Brain Fog? These Hidden Causes Could Signal Dementia

1. Chronic Stress

Chronic stress exerts a profound impact on brain health, often going unnoticed until symptoms arise. When stress is sustained over long periods, the body produces excess amounts of cortisol, the so-called “stress hormone.” Elevated cortisol has been shown to alter brain chemistry, particularly in regions like the hippocampus, which is essential for memory formation and recall. These changes can manifest as memory lapses, confusion, and persistent brain fog—symptoms that closely resemble the early stages of dementia.

Research indicates that chronic stress not only impairs cognitive function but may also accelerate neurodegenerative processes linked to dementia. Cortisol can damage neurons and disrupt synaptic connections, diminishing the brain’s ability to process and retain information. Over time, these effects can contribute to structural changes in the brain, increasing the risk of developing Alzheimer’s disease or other forms of dementia. Recognizing and addressing chronic stress is therefore vital for both mental clarity and long-term brain health. For further insights into the link between stress and dementia, visit this review published by the National Institutes of Health.

2. Poor Sleep Quality

Sleep is fundamental to cognitive function, playing a crucial role in memory consolidation and mental clarity. When sleep is inadequate or frequently disrupted, the brain does not have sufficient time to process information and form lasting memories. This deficit often leads to symptoms such as confusion, forgetfulness, and persistent brain fog—features that are strikingly similar to those seen in the early stages of dementia.

Scientific research has linked poor sleep quality to impaired cognitive processing and increased risk of neurodegenerative diseases. During deep sleep, the brain clears out toxins and consolidates memories. Without this restorative phase, cognitive performance declines and the risk for diseases like Alzheimer’s increases. In fact, chronic sleep problems have been associated with a greater buildup of beta-amyloid plaques, a hallmark of Alzheimer’s disease. Addressing sleep issues early can help safeguard memory and cognitive abilities as we age. For more information on the connection between sleep and dementia, refer to this resource from the Sleep Foundation and this study from the National Institutes of Health.

3. Vitamin B12 Deficiency

Vitamin B12 is essential for maintaining healthy nerve cells and proper brain function. A deficiency in this crucial nutrient can lead to neurological and cognitive problems that closely resemble the symptoms of dementia. Individuals with insufficient B12 levels may experience confusion, memory lapses, difficulty concentrating, and mental fatigue—all of which contribute to the sensation of brain fog.

B12 plays a pivotal role in the production of myelin, the protective sheath around nerves. Without adequate B12, nerve signaling becomes impaired, leading to cognitive disturbances and, in severe cases, permanent nerve damage. These symptoms can be so similar to those of early dementia that misdiagnosis is possible if B12 deficiency is not considered and tested for. Fortunately, cognitive decline caused by B12 deficiency is often reversible if detected and treated early with supplementation or dietary changes. Risk factors for B12 deficiency include aging, certain medications, digestive disorders, and strict vegetarian or vegan diets. For more information on the neurological effects of vitamin B12 deficiency, visit this detailed article from the National Institutes of Health and the overview provided by the Alzheimer’s Society.

4. Hypothyroidism

Hypothyroidism, or an underactive thyroid, is a condition in which the thyroid gland does not produce enough hormones to regulate the body’s metabolism efficiently. This hormonal deficiency can severely impact cognitive functions, resulting in symptoms such as sluggish thinking, forgetfulness, and persistent brain fog. These cognitive problems often mimic the early warning signs of dementia, leading to potential misdiagnosis if thyroid function is not assessed.

Thyroid hormones are vital for brain health, influencing memory, attention, and mental processing speed. When thyroid activity slows, the brain’s metabolism also decreases, impairing the transmission of nerve signals and reducing the production of neurotransmitters involved in cognition. Individuals with hypothyroidism may notice difficulty concentrating, slowed reaction times, and trouble recalling recent events. Fortunately, the cognitive symptoms associated with hypothyroidism are often reversible with proper diagnosis and hormone replacement therapy. Routine screening for thyroid dysfunction is especially important in older adults, where the symptoms can be subtle or attributed to aging. For more information about the link between hypothyroidism and cognitive changes, see the resources from the NHS and this review from the National Institutes of Health.

5. Depression

Depression is a mood disorder that can significantly affect cognitive function, often leading to symptoms such as forgetfulness, lack of concentration, and persistent feelings of mental sluggishness. These cognitive impairments, sometimes referred to as “pseudodementia,” can closely resemble the early stages of dementia, making it challenging for clinicians and families to differentiate between the two conditions. Individuals with depression may experience notable difficulties with memory, decision-making, and processing information, further blurring the line between mood disorders and neurological decline.

The overlap between depressive symptoms and cognitive decline is well-documented. Depression can slow down brain activity, disrupt sleep, and reduce motivation, all of which contribute to cognitive symptoms. In older adults, depression can be particularly deceptive, as mood changes might be less pronounced than cognitive complaints. Distinguishing between depression-related cognitive issues and true dementia is crucial, as the former is often reversible with appropriate treatment such as therapy or medication. Left untreated, depression can exacerbate cognitive problems and potentially increase the long-term risk of developing dementia. For more information, consult this article from the Alzheimer’s Association and research from the National Institutes of Health.

6. Medication Side Effects

Many commonly prescribed and over-the-counter medications can cause significant cognitive side effects, particularly in older adults. Drugs with anticholinergic properties—including certain antihistamines, antidepressants, bladder medications, and muscle relaxants—are particularly notorious for impairing memory, attention, and overall mental clarity. These medications work by blocking acetylcholine, a neurotransmitter crucial for learning and memory, and their usage can lead to confusion, disorientation, and persistent brain fog that closely resembles the early stages of dementia.

The risk is especially high when multiple medications with anticholinergic effects are taken together, a scenario known as a high “anticholinergic burden.” Older adults are more susceptible to these adverse effects, and the cognitive symptoms can sometimes be mistaken for irreversible dementia. In many cases, simply adjusting or discontinuing the offending medication can result in significant cognitive improvement. It is essential for individuals and caregivers to review all medications regularly with a healthcare provider, especially when new symptoms of confusion or memory loss arise. For further details on how medications can affect cognitive function, refer to this resource from the Alzheimer’s Association and this article from the National Institutes of Health.

7. Dehydration

Dehydration, or insufficient fluid intake, is a surprisingly common cause of cognitive impairment, especially among older adults. When the body lacks adequate water, the brain’s ability to function optimally is compromised, often resulting in symptoms such as confusion, disorientation, and memory difficulties. These manifestations can mimic the early signs of dementia, making it crucial to consider hydration status when evaluating sudden cognitive changes.

The aging process itself increases vulnerability to dehydration. Older individuals may have a reduced sense of thirst, take medications that promote fluid loss, or have mobility challenges that make it harder to access fluids. Even mild dehydration can lead to acute confusion or delirium, which can be mistaken for the onset of dementia. Fortunately, these cognitive symptoms are often rapidly reversible with proper hydration. Recognizing the signs of dehydration—such as dry mouth, dizziness, dark urine, and decreased urine output—can prevent unnecessary alarm and help restore cognitive clarity. For more information on how dehydration impacts brain function, visit this resource from the NHS and review this study by the National Institutes of Health.

8. Sleep Apnea

Sleep apnea is a common but often underdiagnosed sleep disorder characterized by repeated interruptions in breathing during sleep. These breathing pauses can last from a few seconds to a minute, resulting in decreased oxygen levels to the brain and frequent awakenings throughout the night. The chronic reduction in oxygen supply impairs neural function and can contribute to significant cognitive issues, including morning confusion, poor concentration, and memory lapses. Over time, these symptoms can closely mimic those of mild cognitive impairment or even early dementia.

People with untreated sleep apnea often experience excessive daytime sleepiness, irritability, and persistent brain fog, all of which can be mistaken for age-related cognitive decline. Research indicates that sleep apnea may even accelerate the progression of neurodegenerative conditions such as Alzheimer’s disease by disrupting the brain’s ability to clear toxins during deep sleep. Early recognition and treatment—such as continuous positive airway pressure (CPAP) therapy—can restore oxygen flow, improve sleep quality, and reduce cognitive symptoms. For more information on the cognitive effects of sleep apnea, refer to this overview by the Sleep Foundation and this research summary from the National Institutes of Health.

9. Diabetes

Diabetes is a chronic condition marked by abnormal blood sugar regulation, which can have far-reaching effects on brain health. Fluctuating blood glucose levels, whether too high (hyperglycemia) or too low (hypoglycemia), damage blood vessels throughout the body, including those supplying the brain. This vascular damage impairs the delivery of oxygen and nutrients to brain cells, leading to cognitive symptoms such as brain fog, slowed thinking, and memory problems. Over time, poorly controlled diabetes significantly increases the risk of developing both vascular dementia and Alzheimer’s disease.

Studies have shown that people with diabetes are at a higher risk of experiencing mild cognitive impairment and dementia compared to those without the condition. Chronic hyperglycemia can promote inflammation and the formation of harmful proteins in the brain, while episodes of hypoglycemia can cause acute confusion and even permanent brain injury if severe. Effective management of blood sugar levels is essential not only for physical health but also for preserving cognitive function. For more on how diabetes affects the brain and raises dementia risk, see this resource from the Alzheimer’s Association and this research from the National Institutes of Health.

10. Urinary Tract Infections (UTIs)

Urinary tract infections (UTIs) are a frequent and often underestimated cause of sudden cognitive changes, particularly among older adults. Unlike younger individuals, who typically experience classic symptoms like pain or burning during urination, seniors may present with acute confusion, disorientation, or even hallucinations when a UTI develops. This sudden mental decline—known as delirium—can easily be mistaken for the onset or rapid worsening of dementia.

The underlying cause of this confusion is believed to be a combination of the body’s inflammatory response to infection and the spread of toxins that can temporarily disrupt brain function. UTIs often go undiagnosed in older adults because the cognitive symptoms overshadow the physical ones. Fortunately, when the infection is identified and treated with antibiotics, mental clarity usually returns to baseline. Recognizing this link is crucial for families and healthcare providers, as prompt diagnosis and treatment can prevent unnecessary distress and complications. For more information about the effects of UTIs on mental status in the elderly, review this article from the National Institute on Aging and this research summary from the National Institutes of Health.

11. Alcohol Abuse

Chronic alcohol abuse is a major risk factor for cognitive decline and increased dementia risk. Prolonged heavy drinking exerts toxic effects on the brain, disrupting the structure and function of neurons and impairing the communication between brain cells. Over time, this neurotoxicity can lead to persistent cognitive impairments such as memory loss, poor judgment, difficulty concentrating, and pronounced brain fog. These symptoms not only diminish quality of life but also closely resemble those of early dementia.

Alcohol-related brain damage is linked to both direct effects—such as the loss of brain volume, especially in regions critical for memory and learning—and indirect effects, including vitamin deficiencies and liver dysfunction, which further compromise brain health. Conditions like Wernicke-Korsakoff syndrome are specific forms of alcohol-induced cognitive decline that can be prevented or mitigated with early recognition and treatment. Studies indicate that people who engage in long-term, heavy drinking are significantly more likely to develop both Alzheimer’s disease and vascular dementia. For more on how alcohol abuse impacts cognitive function and dementia risk, see this overview by the Alzheimer’s Society and this research summary from the National Institutes of Health.

12. Head Injuries

Traumatic brain injuries (TBIs), including concussions and more severe blows to the head, can have lasting consequences on cognitive function. Even a single significant head injury can disrupt normal brain activity, leading to symptoms such as confusion, memory loss, difficulty concentrating, and persistent brain fog. These effects may be temporary for some, but research shows that TBIs can also increase the risk of developing dementia later in life.

The mechanism behind this link involves both immediate and long-term changes in the brain. After a TBI, inflammation, bleeding, and the disruption of neural pathways can impair cognitive abilities. Over time, repeated injuries or even a single severe trauma can accelerate brain atrophy and promote the accumulation of abnormal proteins, which are characteristic of Alzheimer’s disease and other dementias. Older adults, athletes, and individuals with repeated head injuries are especially at risk. Early intervention, cognitive rehabilitation, and protective measures can help reduce long-term consequences. For more information about the relationship between head injuries and cognitive decline, visit the Alzheimer’s Association and review this study from the National Institutes of Health.

13. Hearing Loss

Untreated hearing loss is increasingly recognized as a significant and modifiable risk factor for cognitive decline and dementia. When individuals struggle to hear, the brain must work harder to interpret sounds, diverting cognitive resources away from other vital functions such as memory and reasoning. This increased mental effort can lead to persistent brain fog, reduced attention, and problems with information retention—all symptoms that may resemble early dementia.

Research has shown a strong association between hearing loss and a higher risk of developing cognitive impairment and dementia. One proposed explanation is that the brain undergoes structural changes due to a lack of auditory stimulation, which may accelerate neurodegeneration. Additionally, hearing loss can lead to social isolation and depression, both of which are independent risk factors for cognitive decline. Addressing hearing loss with timely interventions, such as hearing aids or assistive devices, can help preserve cognitive function and improve quality of life. For more information about how hearing loss impacts dementia risk, visit this resource from the National Institute on Aging and read this review from the National Institutes of Health.

14. Social Isolation

Social isolation and loneliness are increasingly recognized as significant threats to brain health and cognitive function, especially among older adults. When individuals lack regular social interaction, the brain receives less stimulation, which can lead to a decline in cognitive abilities over time. Persistent loneliness has been linked to symptoms such as brain fog, difficulty concentrating, and memory lapses—effects that can mimic or exacerbate early dementia.

Numerous studies have demonstrated a robust association between social isolation and an elevated risk of developing dementia. The mechanisms behind this link may include increased stress, higher rates of depression, and reduced opportunities for cognitive engagement, all of which can accelerate neurodegenerative changes. Socially isolated individuals are also more likely to experience health problems such as high blood pressure and weakened immune systems, further compounding their risk of cognitive decline. Encouraging meaningful social connections, participation in community activities, and maintaining regular communication with family and friends can help protect brain health. For further reading on the impact of loneliness and isolation on dementia risk, consult this overview from the Centers for Disease Control and Prevention and this research summary from the National Institutes of Health.

15. Chronic Inflammation

Chronic inflammation is a persistent, low-grade immune response that can develop from conditions such as obesity, autoimmune disorders, infections, or even long-term stress. While inflammation is a natural defense mechanism, its ongoing presence in the body has been linked to a host of health problems, including cognitive decline and an increased risk of dementia. The inflammatory process can cross the blood-brain barrier, leading to neuroinflammation and the gradual breakdown of brain cells.

Neuroinflammation is believed to play a crucial role in the development of Alzheimer’s disease and other forms of dementia. It can accelerate the accumulation of abnormal proteins in the brain, disrupt communication between neurons, and impair the brain’s ability to repair itself. Individuals with chronic inflammatory conditions often report symptoms such as brain fog, impaired memory, and reduced mental sharpness—cognitive effects that may precede or accompany dementia. Addressing the root causes of inflammation through lifestyle changes, medical management, and a healthy diet is vital for preserving cognitive health. For a deeper look at the connection between chronic inflammation and dementia, see this article from the Alzheimer’s Society and this research from the National Institutes of Health.

16. Heavy Metal Exposure

Exposure to heavy metals such as lead, mercury, arsenic, and cadmium poses significant risks to nervous system health. These toxic substances can accumulate in the body over time, damaging neural tissue and interfering with normal brain function. Even low-level, chronic exposure may cause subtle cognitive symptoms, including brain fog, memory loss, and decreased attention span—effects that can resemble the early signs of dementia.

Heavy metals disrupt cellular processes in the brain, promote oxidative stress, and trigger neuroinflammation, all of which contribute to neural degeneration. Both children and adults are susceptible, but older adults may be at greater risk for cognitive decline due to cumulative exposure and reduced detoxification capacity. Sources of heavy metal exposure include contaminated water, old paint, certain seafood, industrial pollution, and some traditional medicines. Limiting exposure and ensuring proper detection and treatment are crucial for protecting cognitive health. For more on how heavy metal toxicity impacts the brain and cognition, see this article from the Centers for Disease Control and Prevention and this research summary from the National Institutes of Health.

17. High Blood Pressure

High blood pressure, or hypertension, is a major risk factor for both vascular and Alzheimer’s dementia. Over time, consistently elevated blood pressure damages the delicate blood vessels throughout the body, including those that supply the brain. This vascular damage can cause the arteries to stiffen and narrow, limiting blood flow and reducing the delivery of oxygen and nutrients essential for healthy brain function. As a result, individuals with uncontrolled hypertension are more likely to experience cognitive symptoms such as brain fog, slowed thinking, and memory lapses.

Reduced cerebral blood flow impairs the brain’s ability to clear metabolic waste and maintain normal neural activity. Chronic hypertension is also linked to small vessel disease and “silent” strokes, which can further compromise cognitive function and accelerate the progression of dementia. Early detection and effective management of high blood pressure through lifestyle changes and medication can lower the risk of cognitive decline. For more information on the impact of hypertension on brain health, see the guidance from the Centers for Disease Control and Prevention and this research review by the National Institutes of Health.

18. Chronic Pain

Chronic pain is more than just a physical burden—it can have far-reaching effects on mental clarity, memory, and overall cognitive health. Persistent pain continuously activates the body’s stress response and demands constant attention from the brain, diverting mental resources away from tasks related to concentration, learning, and memory. As a result, individuals with chronic pain often report symptoms such as brain fog, trouble focusing, and forgetfulness, which can closely resemble the cognitive decline seen in early dementia.

The relationship between chronic pain and cognition is complex. Ongoing pain disrupts sleep, increases anxiety and depression risk, and can even alter brain structure and function over time. Neuroimaging studies have shown that chronic pain can shrink areas of the brain responsible for memory and executive function, accelerating cognitive aging. Addressing chronic pain with effective medical management, physical therapy, and psychological support is essential for preserving both physical and cognitive well-being. For more information on how chronic pain impacts the brain and cognitive function, consult this article from the Harvard Health Blog and this research from the National Institutes of Health.

19. Nutritional Deficiencies

Beyond vitamin B12, deficiencies in other essential nutrients can have a profound impact on brain function and increase the risk of cognitive decline and dementia. Nutrients such as vitamin D, folate, omega-3 fatty acids, iron, and antioxidants play critical roles in maintaining neuronal health, supporting neurotransmitter synthesis, and protecting the brain from oxidative stress. When these nutrients are lacking, individuals may experience symptoms like brain fog, poor concentration, and memory lapses, which can closely mimic or accelerate the progression of dementia.

For example, vitamin D is essential for brain development and immune regulation, while omega-3 fatty acids are crucial for cell membrane integrity and anti-inflammatory processes in the brain. Folate and iron deficiencies are linked to impaired neurotransmitter production and reduced oxygen delivery to the brain, further contributing to cognitive problems. Poor nutritional status is especially common in older adults, individuals with restrictive diets, or those suffering from chronic illness. Ensuring a balanced diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats is vital for cognitive health. For more on the relationship between nutrition and dementia risk, review information from the Alzheimer’s Society and this research from the National Institutes of Health.

20. Sedentary Lifestyle

A sedentary lifestyle—characterized by prolonged periods of physical inactivity—has been shown to negatively impact both body and brain health. Lack of regular movement reduces overall blood flow, including to the brain, which can impair the delivery of oxygen and essential nutrients needed for optimal neural function. This diminished circulation may result in symptoms such as brain fog, slowed thinking, and memory difficulties, which are commonly mistaken for early cognitive decline or dementia.

Physical activity also plays a crucial role in stimulating neurogenesis, the process by which new brain cells are created, particularly in the hippocampus, an area vital for learning and memory. Inactivity not only reduces neurogenesis but also promotes inflammation and increases the risk for chronic diseases like diabetes and hypertension—both of which are linked to dementia. Incorporating regular exercise, even light to moderate activity such as walking, can enhance cognitive performance, improve mood, and help protect against age-related decline. For more information about how a sedentary lifestyle influences brain health and dementia risk, refer to this overview by the Centers for Disease Control and Prevention and this research from the National Institutes of Health.

21. Obstructive Sleep Disorders (Beyond Apnea)

While sleep apnea is widely recognized for its impact on cognitive health, other obstructive sleep disorders—such as restless legs syndrome (RLS) and periodic limb movement disorder—can also significantly disrupt restorative sleep and impair brain function. Restless legs syndrome causes uncomfortable sensations and an irresistible urge to move the legs, particularly at night, often leading to frequent awakenings and poor sleep quality. Similarly, periodic limb movements can fragment sleep cycles, preventing the brain from entering deep, restorative stages essential for memory consolidation and cognitive processing.

Chronic sleep disruption from these conditions is associated with symptoms like brain fog, memory lapses, and difficulty concentrating. Over the long term, sleep disorders that limit deep sleep can contribute to neurodegenerative changes and elevate the risk of developing dementia. Individuals with untreated RLS or other sleep-related movement disorders may also experience increased daytime fatigue, mood disturbances, and a decreased quality of life. Early diagnosis and management—through lifestyle interventions, medications, or sleep hygiene improvements—can help restore sleep quality and protect cognitive health. For more details, consult this resource from the Sleep Foundation and this review from the National Institutes of Health.

22. Heart Disease

Heart disease, encompassing conditions such as heart failure, coronary artery disease, and arrhythmias, is a major contributor to impaired brain health. When the heart’s ability to pump blood effectively is compromised, the brain receives less oxygen and fewer vital nutrients. This reduction in cerebral blood flow can lead to cognitive symptoms such as mental fatigue, confusion, memory problems, and persistent brain fog—signs that can resemble or hasten the onset of dementia.

Research shows that poor cardiac output directly affects the brain’s structure and function, increasing the risk of both vascular dementia and Alzheimer’s disease. Chronic hypoperfusion (low blood flow) can cause white matter lesions, shrinkage in critical brain areas, and impaired clearance of neurotoxic substances. Individuals with heart disease often experience more rapid cognitive decline compared to those with healthy cardiovascular systems. Maintaining heart health through the management of risk factors—such as high blood pressure, cholesterol, and diabetes—along with regular exercise and a heart-healthy diet, is vital for protecting both cardiovascular and cognitive function. For more information on the connection between heart health and cognition, visit the American Heart Association and review this study from the National Institutes of Health.

23. Chronic Kidney Disease

Chronic kidney disease (CKD) not only affects physical health but also has profound implications for cognitive function. As the kidneys lose their ability to effectively filter waste products from the bloodstream, toxins and metabolic byproducts gradually accumulate in the body. This buildup can cross the blood-brain barrier and disrupt normal brain activity, leading to symptoms such as brain fog, decreased mental sharpness, and memory difficulties—cognitive issues that can be mistaken for the early stages of dementia.

Research indicates that individuals with CKD are at higher risk for both mild cognitive impairment and more severe forms of dementia. The underlying mechanisms include chronic inflammation, vascular damage, and imbalances in electrolytes and hormones—all of which can negatively influence brain health. Dialysis can help reduce toxin levels, but cognitive symptoms may persist, particularly in advanced stages of kidney disease. Early detection and management of CKD, along with the treatment of contributing factors like high blood pressure and diabetes, are crucial for preserving cognitive abilities. For more information on how chronic kidney disease impacts the brain, consult this overview from the National Kidney Foundation and this research summary from the National Institutes of Health.

24. Liver Dysfunction

Liver dysfunction, particularly in advanced liver disease, can severely impact brain health by allowing toxins to accumulate in the bloodstream. The liver’s primary role is to filter and detoxify harmful substances; when it fails, ammonia and other metabolic byproducts can reach the brain and disrupt normal neural activity. This condition, known as hepatic encephalopathy, can cause symptoms ranging from mild confusion and forgetfulness to severe disorientation and even coma.

Hepatic encephalopathy is a reversible cause of cognitive impairment and is often mistaken for dementia, especially in older adults. Symptoms include personality changes, mood swings, difficulty concentrating, and “clouded” thinking—collectively referred to as brain fog. Early recognition and treatment, which may involve medications to reduce toxin levels or dietary adjustments, can lead to substantial recovery of mental function. Addressing underlying liver disease is also essential for long-term cognitive health. For more information about the effects of liver dysfunction and hepatic encephalopathy on the brain, see this resource from the Mayo Clinic and this research article from the National Institutes of Health.

25. Uncontrolled Epilepsy

Uncontrolled epilepsy, characterized by frequent or poorly managed seizures, poses a significant threat to cognitive function over time. Each seizure episode can temporarily disrupt neural circuits, and recurrent seizures may cause cumulative damage to brain cells, especially in regions responsible for memory and executive function. As a result, individuals with poorly controlled epilepsy often experience symptoms such as persistent brain fog, memory lapses, slowed thinking, and difficulty concentrating—cognitive issues that can sometimes be mistaken for early signs of dementia.

In addition to the direct effects of seizures, certain anti-seizure medications can have cognitive side effects. These drugs may contribute to drowsiness, attention difficulties, and impaired short-term memory, further complicating the cognitive profile of individuals with epilepsy. Careful management of both the underlying condition and medication regimens is crucial to minimize these risks. Regular neurological assessments and medication reviews can help optimize seizure control while reducing cognitive side effects. For more information on the long-term cognitive impact of epilepsy and its treatments, visit this overview by the Epilepsy Foundation and this research article from the National Institutes of Health.

26. Autoimmune Disorders

Autoimmune disorders such as systemic lupus erythematosus (lupus), multiple sclerosis, and Sjögren’s syndrome occur when the immune system mistakenly attacks the body’s own tissues, including those of the brain and nervous system. In these conditions, chronic inflammation can develop within the brain—a phenomenon known as neuroinflammation. This inflammatory response can disrupt normal neural signaling, leading to cognitive symptoms including confusion, memory difficulties, poor concentration, and persistent brain fog.

Lupus, for example, is well known for its neuropsychiatric manifestations, which can range from subtle cognitive changes to severe episodes of delirium or psychosis. These symptoms are sometimes referred to as “lupus brain” or lupus cerebritis. The cognitive effects of autoimmune disorders may be mistaken for early dementia, especially if they occur gradually or fluctuate in severity. Prompt diagnosis and management with immunosuppressive medications can help control inflammation and often lead to improvement in cognitive function. For more information about how autoimmune diseases affect the brain and cognition, refer to this resource from the Lupus Foundation of America and this research review from the National Institutes of Health.

27. Chronic Obstructive Pulmonary Disease (COPD)

Chronic Obstructive Pulmonary Disease (COPD) is a progressive lung condition that restricts airflow and impairs the exchange of oxygen and carbon dioxide in the body. As COPD advances, blood oxygen levels may drop, a state known as hypoxemia. The brain is highly sensitive to even small reductions in oxygen supply, and persistent hypoxemia can lead to cognitive symptoms such as brain fog, confusion, trouble concentrating, and forgetfulness—effects that can be mistaken for dementia, particularly in older adults.

Studies have shown that individuals with COPD are at a higher risk for cognitive impairment and even dementia, especially if their oxygen levels are not adequately managed. Chronic low oxygen impairs neuronal metabolism, increases oxidative stress, and may even result in small areas of brain damage. Managing COPD with medications, supplemental oxygen, and lifestyle changes can help mitigate these cognitive effects and improve overall quality of life. Recognizing and addressing cognitive changes early is crucial, as some symptoms may be reversible with better oxygenation. For more details on the impact of COPD on cognition, see this resource from the American Lung Association and this research from the National Institutes of Health.

28. Hormonal Imbalances (Other Than Thyroid)

Hormonal imbalances involving estrogen, testosterone, cortisol, and insulin can significantly affect brain function and mood, leading to symptoms such as brain fog, memory lapses, and difficulty concentrating. Estrogen, for example, plays a crucial role in protecting neurons, supporting synaptic plasticity, and regulating neurotransmitter systems involved in cognition. Declining estrogen levels during menopause are associated with increased forgetfulness, trouble focusing, and mood swings—symptoms sometimes referred to as “menopause brain.”

Similarly, low testosterone in men has been linked to reduced mental clarity, decreased motivation, and a greater risk of depression. Imbalances in other hormones, such as elevated cortisol from chronic stress or disrupted insulin signaling in diabetes, can also impair cognitive processes and emotional stability. These hormonal changes may mimic or exacerbate early signs of dementia if left unaddressed. Addressing hormonal imbalances through medical evaluation, hormone replacement therapy when appropriate, and healthy lifestyle changes can help restore both cognitive and emotional well-being. For more on the impact of non-thyroid hormonal imbalances on cognition and mood, refer to this overview from the Harvard Health and this research summary from the National Institutes of Health.

29. Sleep Deprivation (Acute)

Acute sleep deprivation, defined as a single night or short period of insufficient sleep, can have immediate and noticeable effects on cognitive performance. Even one night of poor or disrupted sleep can impair working memory, slow reaction times, and reduce the ability to concentrate. These symptoms, often described as “brain fog,” can mimic those seen in the early stages of dementia, leading to temporary confusion, forgetfulness, and difficulty processing information.

The brain relies on sleep to consolidate memories, clear metabolic waste, and restore neural connections. Lack of adequate rest disrupts these processes, resulting in reduced attention span and impaired decision-making the following day. While the cognitive consequences of acute sleep deprivation are typically reversible with recovery sleep, chronic patterns of poor sleep can increase long-term dementia risk. Recognizing the impact of even short-term sleep loss on mental clarity highlights the importance of prioritizing good sleep hygiene. For further information on how acute sleep deprivation affects memory and cognitive function, see this article from the Sleep Foundation and this research review from the National Institutes of Health.

30. Smoking

Smoking is a well-established risk factor for cognitive decline and dementia, with its harmful effects stemming largely from damage to blood vessels and impaired oxygen delivery to the brain. Tobacco use accelerates atherosclerosis, or the buildup of plaque in the arteries, which narrows blood vessels and restricts blood flow. As a result, the brain receives less oxygen and fewer nutrients, leading to chronic “brain fog,” memory impairment, and slowed processing speed—symptoms commonly seen in the early stages of dementia.

Chemicals in tobacco smoke also contribute to oxidative stress and inflammation, both of which can damage neurons and promote the formation of abnormal proteins associated with Alzheimer’s disease. Studies have shown that smokers are at higher risk for both vascular dementia and Alzheimer’s disease compared to non-smokers. The cognitive benefits of quitting smoking are significant, as cessation can help restore blood flow, reduce inflammation, and slow or even reverse vascular damage. For more on the relationship between smoking and dementia risk, review this resource from the Alzheimer’s Society and this research summary from the National Institutes of Health.

31. Hyponatremia (Low Sodium)

Hyponatremia, a condition characterized by abnormally low sodium levels in the blood, can have a profound impact on brain function. Sodium plays a crucial role in maintaining the electrical activity of nerve cells and regulating fluid balance within the body and brain. When sodium levels drop too low—due to illness, excessive fluid intake, certain medications (such as diuretics or antidepressants), or underlying hormonal imbalances—the brain can swell, leading to neurological symptoms.

The cognitive effects of hyponatremia often manifest as confusion, disorientation, attention deficits, and memory problems—symptoms that can closely resemble the early stages of dementia or delirium. In severe cases, individuals may experience seizures, decreased consciousness, or even coma. The elderly are particularly vulnerable, as age-related changes and polypharmacy increase the risk of sodium imbalance. Fortunately, correcting the underlying cause of hyponatremia usually leads to a rapid improvement in cognitive symptoms. Prompt recognition and appropriate management are critical for preventing serious complications. For more information on how low sodium levels affect cognition, refer to this overview from the Mayo Clinic and this clinical review from the National Institutes of Health.

32. Chemotherapy (Chemo Brain)

The phenomenon known as “chemo brain” refers to cognitive changes experienced by many individuals undergoing cancer treatment, particularly chemotherapy. Common symptoms include memory lapses, difficulty concentrating, trouble finding words, slowed thinking, and persistent mental fog. These effects can be distressing, sometimes resembling the cognitive difficulties seen in early dementia, though chemo brain is generally considered temporary and reversible for most people.

The exact cause of chemo brain is not fully understood, but it is believed to result from a combination of direct effects of chemotherapy drugs on the brain, inflammation, fatigue, anemia, and emotional stress related to cancer diagnosis and treatment. Some individuals may experience cognitive symptoms for months or even years after completing treatment, while others recover more quickly. Supportive strategies such as cognitive exercises, adequate rest, and stress reduction can help manage symptoms. Awareness of chemo brain is important so that patients and caregivers can distinguish it from other causes of cognitive decline. For further information, see this resource from the National Cancer Institute and this review from the National Institutes of Health.

33. Anxiety Disorders

Chronic anxiety disorders, such as generalized anxiety disorder, panic disorder, and social anxiety disorder, can significantly impair cognitive function. Persistent anxiety floods the body with stress hormones like cortisol, which can disrupt neural pathways involved in memory, attention, and executive function. As a result, individuals with unmanaged anxiety often experience symptoms like difficulty concentrating, forgetfulness, and persistent mental fog—symptoms that can closely resemble those of early dementia.

The cognitive effects of anxiety are sometimes referred to as “anxiety-induced cognitive impairment” or “brain fog.” These symptoms may fluctuate with the severity of anxiety and are often reversible with effective treatment. Unfortunately, chronic anxiety can also exacerbate underlying risks for cognitive decline, particularly when it leads to sleep disturbances or social withdrawal. Differentiating anxiety-related cognitive changes from those of neurodegenerative conditions is crucial, as anxiety is highly treatable through therapy, medication, and lifestyle interventions. For more information about the impact of anxiety on cognition and its potential to mimic dementia, visit this resource from the Alzheimer’s Association and review this research summary from the National Institutes of Health.

34. Bipolar Disorder

Bipolar disorder is a mood disorder characterized by episodes of depression and mania or hypomania, both of which can significantly impact cognitive function. During depressive episodes, individuals may experience slowed thinking, poor concentration, and memory difficulties. Conversely, manic episodes can bring about distractibility and impulsivity, making it challenging to focus or retain new information. These fluctuations in cognitive performance can sometimes be mistaken for the early stages of dementia, particularly in older adults.

In addition to mood-related cognitive changes, certain medications commonly used to manage bipolar disorder, such as lithium and some antipsychotics, can have cognitive side effects. These may include mental sluggishness, difficulty with word-finding, and impaired short-term memory. While these effects are often mild and manageable, they can add to the cognitive burden already posed by the disorder itself. Careful medication management and regular monitoring by healthcare professionals can help minimize these cognitive effects. For further reading on the relationship between bipolar disorder, cognition, and dementia risk, see this overview from the Alzheimer’s Society and this research article from the National Institutes of Health.

35. Lyme Disease

Lyme disease, caused by the bacterium Borrelia burgdorferi and transmitted through tick bites, can have severe neurological consequences if left untreated. In some cases, the infection spreads to the central nervous system, a complication known as neuroborreliosis. This condition can cause a range of cognitive symptoms, including confusion, difficulty concentrating, memory loss, and persistent brain fog. These effects may be mistaken for early dementia, particularly in older adults or those with preexisting health issues.

Neuroborreliosis results from inflammation of the brain and surrounding tissues, disrupting normal neural communication and impairing cognitive function. Symptoms can fluctuate in severity and may be accompanied by mood changes, sleep disturbances, and neuropathic pain. Early diagnosis and prompt antibiotic treatment are critical for minimizing long-term neurological damage. In most cases, cognitive symptoms improve with successful treatment, although recovery may take time. For more information on the cognitive effects of Lyme disease and neuroborreliosis, see this resource from the Centers for Disease Control and Prevention and this clinical review from the National Institutes of Health.

36. Untreated Sleep Disorders (e.g., Narcolepsy)

Sleep disorders beyond sleep apnea, such as narcolepsy, insomnia, and circadian rhythm disorders, can have a profound impact on cognitive health if left untreated. Narcolepsy, for instance, is characterized by excessive daytime sleepiness and sudden “sleep attacks,” which can significantly disrupt daily functioning. Individuals with narcolepsy or chronic insomnia often experience persistent brain fog, memory lapses, difficulty concentrating, and slowed reaction times—symptoms that can be mistaken for early dementia.

These disorders interfere with the brain’s ability to achieve restorative sleep, which is essential for memory consolidation, toxin clearance, and overall neural health. Chronic sleep fragmentation or deprivation impairs attention, executive function, and information processing. Over time, untreated sleep disorders may increase the risk of developing long-term cognitive decline or neurodegenerative diseases. Early diagnosis and management, through behavioral therapies, medication, and improved sleep hygiene, can help restore cognitive clarity and reduce the risk of misdiagnosis. For more information about how sleep disorders like narcolepsy affect cognition, consult this overview from the Sleep Foundation and this research article from the National Institutes of Health.

37. Celiac Disease and Gluten Sensitivity

Celiac disease is an autoimmune condition triggered by the ingestion of gluten, a protein found in wheat, barley, and rye. In individuals with celiac disease, exposure to gluten causes the immune system to attack the small intestine, leading to inflammation and impaired nutrient absorption. Beyond gastrointestinal symptoms, celiac disease can also manifest with neurological and cognitive issues, including persistent brain fog, memory problems, confusion, and difficulty concentrating. These symptoms may be present even in the absence of classic digestive complaints and can resemble early dementia, especially if left untreated.

Non-celiac gluten sensitivity, while not autoimmune, can also provoke cognitive fog and mental sluggishness after gluten consumption. The mechanisms may involve immune activation and inflammation affecting the brain. Adhering to a strict gluten-free diet is the cornerstone of treatment for celiac disease and typically results in significant improvement in cognitive and neurological symptoms. Awareness of the neurological impact of gluten-related disorders is essential for timely diagnosis and intervention. For more information about how celiac disease and gluten sensitivity can affect brain health, visit the Celiac Disease Foundation and review this research article from the National Institutes of Health.

38. Multiple Sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease in which the immune system attacks the protective myelin sheath covering nerve fibers in the central nervous system. This damage disrupts the efficient transmission of electrical signals between the brain and body, leading to a variety of neurological symptoms. Cognitive changes are common in MS and may include brain fog, slowed thinking, impaired memory, reduced attention span, and difficulty with problem-solving or planning. These cognitive issues can fluctuate in severity and sometimes resemble early signs of dementia.

MS-related cognitive impairment is believed to result from both the direct loss of myelin and the subsequent degeneration of nerve fibers. Inflammation and lesion formation within the brain can further contribute to difficulties with information processing and executive function. While not everyone with MS experiences significant cognitive decline, up to 65% of individuals report some degree of cognitive difficulty during the course of their illness. Early intervention, disease-modifying therapies, cognitive rehabilitation, and lifestyle adjustments can help manage symptoms and support brain health. For more information on the cognitive effects of multiple sclerosis, visit the National Multiple Sclerosis Society and this research review from the National Institutes of Health.

39. Exposure to Toxic Molds

Exposure to toxic molds, particularly those producing mycotoxins such as Stachybotrys chartarum (commonly known as black mold), can have severe effects on brain health. Mycotoxins are toxic compounds released by certain molds found in damp or water-damaged indoor environments. When inhaled or ingested, these substances can trigger a wide array of neurocognitive symptoms, including persistent brain fog, confusion, memory loss, difficulty concentrating, and even mood disturbances. These effects can sometimes be mistaken for the onset of dementia, especially in sensitive or immunocompromised individuals.

Mycotoxins may cause inflammation in the brain, disrupt neurotransmitter function, and impair mitochondrial activity, all of which contribute to cognitive dysfunction. Prolonged exposure increases the risk of more severe neurological and systemic symptoms. Addressing mold-related illness involves identifying and removing the source of mold, improving ventilation, and sometimes medical intervention to treat symptoms or support detoxification. For more information about the neurocognitive impact of toxic mold exposure, consult this resource from the Centers for Disease Control and Prevention and this research review from the National Institutes of Health.

40. Chronic Fatigue Syndrome

Chronic Fatigue Syndrome (CFS), also known as myalgic encephalomyelitis (ME), is a complex disorder characterized by profound, persistent fatigue that is not relieved by rest and is often worsened by physical or mental activity. Alongside extreme tiredness, individuals with CFS commonly experience “brain fog,” which includes difficulties with memory, concentration, information processing, and word-finding. These cognitive symptoms can be severe enough to interfere with daily functioning and are sometimes mistaken for early signs of dementia.

The exact cause of CFS remains unclear, but research suggests that immune dysfunction, hormonal imbalances, and abnormal responses to stress may contribute to both fatigue and neurocognitive symptoms. Patients often report that mental exertion quickly exacerbates their cognitive issues, further distinguishing CFS from typical age-related cognitive decline. There is no cure for CFS, but symptom management—such as pacing activities, cognitive behavioral therapy, and tailored medical interventions—can provide relief. For more on the cognitive impact of Chronic Fatigue Syndrome, see this information from the Centers for Disease Control and Prevention and this research review from the National Institutes of Health.

41. Fibromyalgia

Fibromyalgia is a chronic pain disorder characterized not only by widespread musculoskeletal pain but also by a range of cognitive symptoms commonly referred to as “fibro fog.” Individuals with fibromyalgia often report difficulties with memory, attention, verbal fluency, and mental clarity. This “fibro fog” can manifest as forgetfulness, confusion, an inability to concentrate, and slowed thinking—symptoms that may be mistaken for early dementia, particularly in older adults.

The underlying mechanisms of fibro fog are not completely understood, but research suggests that chronic pain, sleep disturbances, and abnormal levels of neurotransmitters may all contribute to cognitive dysfunction. Stress and emotional distress associated with persistent pain can further exacerbate cognitive symptoms. While there is no cure for fibromyalgia, effective management—including pain relief strategies, regular exercise, cognitive behavioral therapy, and sleep hygiene—can help reduce both physical and cognitive symptoms. Recognizing fibro fog as a legitimate and common part of fibromyalgia is important for accurate diagnosis and support. For more information on the cognitive symptoms of fibromyalgia, see this overview from the Arthritis Foundation and this research review from the National Institutes of Health.

42. Parkinson’s Disease

Parkinson’s disease is a progressive neurodegenerative disorder best known for its impact on movement, such as tremors, rigidity, and slowed motion. However, it can also significantly affect cognitive function. Many individuals with Parkinson’s experience difficulties with memory, attention, executive function, and mental processing speed. Confusion, forgetfulness, and trouble organizing thoughts—sometimes collectively referred to as “Parkinson’s disease dementia”—can appear during the disease’s later stages but may also manifest earlier as mild cognitive impairment.

The cognitive symptoms of Parkinson’s disease are believed to stem from the loss of dopamine-producing neurons, which disrupts communication between different brain regions. In addition to dopamine, changes in other neurotransmitters like acetylcholine can further impact cognition and mood. These cognitive changes may fluctuate in severity and can be worsened by certain medications, infections, or other health issues. Early recognition and intervention, including cognitive training, medication adjustments, and support therapies, can help manage symptoms and maintain quality of life. For more information on the cognitive effects of Parkinson’s disease, see this resource from the Parkinson’s Foundation and this research review from the National Institutes of Health.

43. Early-Onset Alzheimer’s Disease

Early-onset Alzheimer’s disease refers to cases where symptoms develop before the age of 65, sometimes as early as in a person’s 40s or 50s. Unlike typical late-onset Alzheimer’s, early cases often begin with subtle cognitive changes that can be easily overlooked or misattributed to stress or normal aging. One of the first warning signs may be persistent brain fog—feelings of mental sluggishness, trouble concentrating, and difficulty planning or organizing tasks—well before the hallmark symptom of profound memory loss becomes evident.

These early symptoms can lead to challenges at work, problems managing daily responsibilities, and increased frustration or anxiety. As the disease progresses, more noticeable memory lapses, confusion, and language difficulties emerge. Because early-onset Alzheimer’s is rare, these initial signs are sometimes misdiagnosed as depression, burnout, or another neurological condition. Early diagnosis is crucial for accessing treatment options, planning for the future, and potentially participating in clinical trials. For more information on how early-onset Alzheimer’s disease may present and how to seek help, visit the Alzheimer’s Association and review this research from the National Institutes of Health.

44. Untreated High Cholesterol

Untreated high cholesterol is a significant risk factor for vascular problems that extend beyond heart health and can negatively impact cognitive function. Elevated levels of low-density lipoprotein (LDL) cholesterol contribute to the formation of plaques in the arteries, including those that supply blood to the brain. Over time, this buildup—known as atherosclerosis—can narrow or block cerebral arteries, restricting the flow of oxygen and nutrients necessary for healthy brain activity. The result may be symptoms such as brain fog, slowed thinking, memory lapses, and an increased risk of stroke or vascular dementia.

Studies have shown that midlife high cholesterol is associated with a greater risk of developing Alzheimer’s disease and other forms of dementia later in life. The damage to blood vessels not only impedes circulation but can also trigger inflammation and oxidative stress, further harming brain cells. Managing cholesterol through diet, exercise, and medication when necessary is crucial for preserving both cardiovascular and cognitive health. For further information on how high cholesterol affects brain function and dementia risk, see this resource from the American Heart Association and this research review from the National Institutes of Health.

45. Encephalitis

Encephalitis is an acute inflammation of the brain, most often caused by viral infections such as herpes simplex, West Nile virus, or enteroviruses. Bacterial, fungal, or autoimmune causes are also possible. The inflammation resulting from encephalitis disrupts normal brain function, leading to a wide range of neurological and cognitive symptoms. Common manifestations include confusion, memory loss, changes in behavior, difficulty with speech, and severe brain fog. In some cases, seizures or loss of consciousness may occur.

The cognitive changes associated with encephalitis can be profound and may persist even after the acute infection has resolved. Early symptoms are sometimes mistaken for psychiatric disorders or the onset of dementia, especially in older adults. Prompt diagnosis and treatment with antiviral, antibiotic, or immunosuppressive therapies are essential to limit brain damage and improve outcomes. Rehabilitation, including cognitive therapy, may help individuals recover lost functions over time. For more information on the cognitive effects and management of encephalitis, visit this resource from the Centers for Disease Control and Prevention and review this article from the National Institutes of Health.

46. Delirium

Delirium is a sudden, severe state of confusion that often develops over hours or days and is typically triggered by acute illness, surgery, infection, medication changes, or metabolic disturbances. Unlike dementia, which is chronic and progressive, delirium is an acute, fluctuating condition that can present with disorientation, attention deficits, hallucinations, agitation, and significant memory problems. In older adults, delirium is particularly common during hospitalizations or after surgical procedures and is frequently mistaken for the onset or rapid worsening of dementia.

The underlying causes of delirium are varied but generally involve disruptions in brain metabolism or neurotransmitter function. Risk factors include advanced age, preexisting cognitive impairment, dehydration, infection, and polypharmacy. Recognizing delirium promptly is crucial, as it is often reversible when the underlying cause is identified and treated. Delirium not only causes distress for patients and families but is also associated with poorer health outcomes if not addressed. For more information on the symptoms, causes, and treatment of delirium, consult this overview from the National Institute on Aging and this research article from the National Institutes of Health.

47. Long COVID

Long COVID, also known as post-acute sequelae of SARS-CoV-2 infection (PASC), refers to lingering symptoms that persist for weeks or months after the initial COVID-19 infection has resolved. One of the most frequently reported and disruptive symptoms is persistent brain fog—a constellation of cognitive difficulties that includes trouble with memory, attention, processing speed, and word-finding. Many individuals with long COVID describe feeling mentally sluggish, easily distracted, or unable to concentrate, sometimes to the extent that daily functioning is affected.

The mechanisms behind COVID-related brain fog are still being studied but may include ongoing inflammation, immune system dysregulation, vascular damage, or direct viral effects on neural tissue. These cognitive symptoms can occur even in people who had mild or moderate initial illness and may overlap with fatigue, sleep disturbances, and mood changes. Early research suggests that most people improve over time, but some may experience prolonged or even chronic cognitive symptoms. Recognizing long COVID as a potential cause of new or persistent brain fog is important for timely support and rehabilitation. For more information, see this overview from the Centers for Disease Control and Prevention and this research summary from the National Institutes of Health.

48. HIV/AIDS-Related Neurocognitive Disorders

HIV/AIDS-related neurocognitive disorders (HAND) are a group of conditions that affect the central nervous system in individuals living with untreated or advanced HIV infection. The virus can cross the blood-brain barrier and directly infect brain cells, leading to inflammation, neuronal damage, and disruption of normal cognitive processes. As a result, people with HAND may experience symptoms such as confusion, memory loss, slowed thinking, difficulty concentrating, and changes in motor skills or behavior—symptoms that can be mistaken for dementia in severe cases.

The risk of neurocognitive complications increases as HIV progresses, especially if antiretroviral therapy (ART) is not started early or consistently maintained. With effective HIV treatment, the incidence and severity of HAND have decreased, but milder forms of cognitive impairment still affect a significant portion of people living with HIV. Ongoing monitoring, early intervention, and adherence to ART are key to minimizing the impact of neurocognitive disorders. For more information about HIV/AIDS-related impacts on brain health, visit this resource from the National Institute of Mental Health and review this clinical guide from the National Institutes of Health.

49. Sepsis and Systemic Infections

Sepsis is a life-threatening reaction to a systemic infection, marked by widespread inflammation throughout the body. When infection spreads via the bloodstream, the resulting inflammatory response can quickly disrupt brain function, leading to acute confusion, disorientation, agitation, and memory difficulties—a syndrome commonly known as “septic encephalopathy.” These cognitive changes can develop rapidly and often mimic the symptoms of dementia or delirium, making diagnosis challenging, especially in older adults or those with underlying cognitive impairment.

The mechanism behind sepsis-induced cognitive dysfunction involves inflammatory mediators crossing the blood-brain barrier, impairing neurotransmitter balance, and reducing cerebral blood flow. Prompt recognition and treatment of sepsis are critical, as prolonged or severe cases can lead to lasting neurological deficits or even permanent cognitive decline. Survivors of sepsis may continue to experience memory and concentration problems for months or years after recovery. For more information about how sepsis and systemic infections can impact cognition, visit this overview from the Sepsis Alliance and review this research summary from the National Institutes of Health.

50. Brain Tumors

Brain tumors, whether benign or malignant, can produce a wide range of neurological symptoms depending on their size, location, and rate of growth. One of the earliest and most subtle signs may be changes in cognition, including brain fog, memory lapses, confusion, difficulty concentrating, or changes in personality. These cognitive symptoms can sometimes precede more obvious neurological signs such as headaches, seizures, or problems with movement and speech, making early detection challenging.

Tumors may cause cognitive dysfunction by directly compressing or infiltrating brain tissue, disrupting neural pathways, or increasing intracranial pressure. The specific cognitive deficits will vary depending on which part of the brain is affected—for instance, tumors in the frontal lobes often impact judgment and executive function, while those in the temporal lobes may impair memory. Early evaluation and neuroimaging are critical if new or unexplained cognitive symptoms arise, particularly in the absence of other risk factors for dementia. For more information on how brain tumors can cause cognitive changes, visit this resource from the American Cancer Society and review this research article from the National Institutes of Health.

Conclusion

Unexplained or persistent brain fog should never be dismissed, as it may signal an underlying medical condition—including causes that are reversible or treatable if identified early. Timely screening and consultation with a healthcare provider are essential for anyone experiencing ongoing cognitive changes, confusion, or memory lapses. Early intervention can dramatically improve outcomes by distinguishing between reversible factors and the onset of true dementia. Recognizing these subtle symptoms empowers individuals and families to seek appropriate care and support. For more guidance on cognitive health and when to seek help, visit the CDC Alzheimer’s and Dementia Resource and the Alzheimer’s Association.

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