Dementia with Lewy bodies is a complex brain disorder that affects thinking, movement, behavior, and sleep, caused by abnormal protein deposits that damage nerve cells throughout the brain.

Dementia with Lewy bodies, often called DLB, stands as one of the most challenging forms of dementia that a person can face. This condition emerges when clumps of a specific protein called alpha-synuclein begin to accumulate inside brain cells. These abnormal deposits, known as Lewy bodies, were first discovered more than a century ago by Dr. Friedrich Lewy while he worked in Dr. Alois Alzheimer’s laboratory. Today, we understand that these protein clumps interfere with how brain cells communicate with each other, gradually damaging the parts of the brain responsible for thinking, memory, movement, and automatic body functions.^[1]

The disease develops slowly over time, with symptoms that can vary dramatically from one person to another. What makes this condition particularly distinctive is that it doesn’t just affect memory—it creates a constellation of symptoms that touch nearly every aspect of a person’s life. Unlike some other forms of dementia, memory problems may not appear as the earliest warning sign. Instead, people might first notice vivid hallucinations, sudden changes in alertness, movement difficulties similar to Parkinson’s disease, or unusual sleep behaviors where they physically act out their dreams.^[2]

Understanding dementia with Lewy bodies requires looking at it as part of a broader family of related conditions. The term “Lewy body dementia” actually serves as an umbrella that covers both dementia with Lewy bodies and Parkinson’s disease dementia. The key difference lies in which symptoms appear first. When cognitive problems and memory issues show up before or at the same time as movement problems, doctors call it dementia with Lewy bodies. When movement difficulties typical of Parkinson’s disease appear first and cognitive decline develops later, it’s diagnosed as Parkinson’s disease dementia. Despite these different starting points, both conditions share the same underlying cause—those troublesome Lewy body proteins building up in the brain.^[3]

Epidemiology

Dementia with Lewy bodies affects a substantial number of people, though it remains less well-known than Alzheimer’s disease. In the United States alone, more than one million people live with this diagnosis, making it one of the most common forms of dementia. Some experts estimate that approximately 1.4 million individuals across the country are affected by Lewy body dementias as a whole, which includes both dementia with Lewy bodies and Parkinson’s disease dementia.^[4][6]

After Alzheimer’s disease, dementia with Lewy bodies stands as the second most common type of progressive dementia. Among adults over the age of 65, this condition accounts for a significant portion of dementia cases. Research suggests that DLB may represent up to 15 percent of all dementia cases, though many diagnoses are missed or mistaken for other conditions. The actual prevalence in the general population of older adults is estimated at about 0.4 percent of those over 65 years of age.^[5][8]

This condition typically begins in people aged 50 or older, though younger individuals can occasionally develop it as well. The average age at diagnosis tends to be around 76 years. Research has shown that the disease appears to affect men slightly more often than women, though the reasons for this difference remain unclear. Understanding these demographic patterns helps researchers identify who might be at higher risk and ensures that healthcare providers remain vigilant in recognizing the condition in vulnerable populations.^[1][8]

Causes

The fundamental cause of dementia with Lewy bodies lies in the abnormal accumulation of a protein called alpha-synuclein within brain cells. Under normal circumstances, this protein exists throughout the brain, though scientists still don’t fully understand its usual function. In people with DLB, this protein begins to clump together, forming deposits called Lewy bodies inside neurons, which are the nerve cells that make up the brain. These clumps also form thread-like structures called Lewy neurites. Together, these abnormal protein deposits disrupt the normal functioning of brain cells and eventually cause them to die.^[1]

The protein deposits affect multiple regions of the brain simultaneously, particularly those areas responsible for thinking, visual perception, memory, and muscle movement. They also damage parts of the nervous system that control automatic bodily functions, which explains why people with this condition often experience problems with blood pressure regulation, digestion, temperature control, and bladder function. The widespread nature of these deposits throughout the brain explains why the disease creates such a diverse range of symptoms affecting so many different body systems.^[7]

What triggers the formation of these abnormal protein deposits remains a mystery to researchers. Scientists don’t yet know why some people develop these Lewy bodies while others don’t. The deposits appear to interfere with chemical messengers in the brain that allow cells to communicate with each other. When these signals get disrupted, the brain struggles to carry out its normal functions, leading to the cognitive, movement, behavioral, and other symptoms characteristic of the disease.^[4]

Dementia with Lewy bodies usually occurs sporadically, meaning it appears without any clear family history or inheritance pattern. The vast majority of cases arise in people with no relatives affected by the condition. However, there have been extremely rare instances where the disease seems to run in families, suggesting that genetic factors might play a role in some cases. Still, these familial cases represent a very small minority of all DLB diagnoses.^[7]

Risk Factors

Age stands out as the most significant risk factor for developing dementia with Lewy bodies. The condition overwhelmingly affects individuals who are 50 years old or older, with most people receiving their diagnosis well into their later years. The risk continues to increase as people age, with the condition being particularly common in those over 65. While younger people can develop this form of dementia, such cases remain uncommon.^[1]

Having a biological family member with dementia with Lewy bodies or Parkinson’s disease appears to increase a person’s risk of developing the condition. This familial connection suggests that genetic factors may contribute to susceptibility, even though most cases occur in people without affected relatives. Researchers have identified certain genetic variants that may raise the chances of developing dementia with Lewy bodies. Two genes in particular, called APOE and GBA, have been associated with increased risk. However, carrying these genetic variants doesn’t guarantee that someone will develop the disease—it only means they face a higher likelihood compared to those without these variants.^[5]

The slight predominance of the condition in men compared to women represents another demographic pattern, though researchers haven’t determined why this gender difference exists. Scientists continue to study other potential factors that might increase the risk of developing dementia with Lewy bodies, but much remains to be discovered about what makes certain individuals more vulnerable to this condition than others.^[1]

Symptoms

Dementia with Lewy bodies creates a remarkably diverse array of symptoms that affect multiple aspects of a person’s functioning. The severity and combination of symptoms can differ widely from one individual to another, and not everyone experiences all possible symptoms. This variability makes the condition challenging to recognize and diagnose, particularly in its early stages.^[2]

Visual hallucinations stand among the most characteristic symptoms of this condition. Up to 80 percent of people with dementia with Lewy bodies experience these hallucinations, often quite early in the disease’s progression. Individuals may see animals, people, or objects that aren’t actually present. Sometimes they might also hear sounds or voices, smell odors, or feel sensations that don’t have a real source. These hallucinations can range from benign to frightening, and they tend to recur regularly. Unlike hallucinations in some other conditions, those in DLB are typically well-formed and detailed.^[4]

Problems with thinking and cognition represent another core feature of the disease. People may struggle with attention, concentration, and staying alert. They might have difficulty planning activities, solving problems, making decisions, or handling multiple tasks at once. Visual and spatial abilities often suffer, leading to trouble judging distances and depths or difficulty recognizing objects. While memory problems do occur, they may not be as prominent or appear as early as they do in Alzheimer’s disease. Language difficulties can emerge, with people finding it hard to find the right words or follow conversations.^[2]

One of the most distinctive features of dementia with Lewy bodies involves dramatic fluctuations in cognitive function, attention, and alertness. These changes can happen within minutes or hours, creating an unpredictable pattern. A person might seem extremely drowsy, confused, or disconnected one moment, then suddenly become much more alert and capable. They might stare into space for extended periods or experience episodes where their thinking becomes extremely muddled. These fluctuations can be disconcerting for both the person experiencing them and their caregivers.^[7]

Movement problems similar to those seen in Parkinson’s disease frequently occur in dementia with Lewy bodies. This parkinsonism includes symptoms such as muscle stiffness and rigidity, slowed movements, tremors or shaking (often in the hands), a shuffling way of walking, problems with balance that increase fall risk, reduced facial expressions, and difficulties with speech or swallowing. These movement symptoms may appear at the same time as cognitive problems or develop later in the disease course.^[2]

Sleep disturbances represent another hallmark of the condition. Many people with DLB experience a disorder called REM sleep behavior disorder, where they physically act out their dreams while sleeping. This might involve talking, shouting, moving their arms and legs, or even getting out of bed during dreams. The condition occurs because people lose the normal muscle paralysis that typically prevents movement during the dreaming stage of sleep. This sleep disorder can appear years or even decades before other symptoms of dementia with Lewy bodies become apparent. Other sleep problems include excessive daytime sleepiness, trouble falling or staying asleep at night, and restless legs syndrome.^[4]

Mood and behavioral changes frequently accompany the disease. Depression affects many people with this condition and can significantly impact quality of life. Anxiety, apathy (lack of interest or motivation), agitation, and restlessness may also occur. Some individuals develop delusions—false beliefs that persist despite evidence to the contrary. For example, they might become convinced that a spouse is being unfaithful or that someone is trying to harm them. These psychiatric symptoms can be just as challenging as the cognitive and physical difficulties.^[6]

Problems with the autonomic nervous system—the part of the nervous system that controls automatic body functions—create additional complications. Blood pressure may drop suddenly when standing up, causing dizziness, lightheadedness, or fainting. Temperature regulation becomes unreliable, with people having difficulty staying warm or cool. Digestive problems are extremely common, with constipation being one of the most frequent complaints. People may have trouble controlling their bladder or bowels. Sweating patterns may change. Sexual function can be affected. An early loss of the sense of smell often occurs, sometimes years before other symptoms appear.^[2][5]

Prevention

Currently, no proven methods exist to prevent dementia with Lewy bodies. Scientists don’t yet understand enough about what triggers the formation of Lewy body proteins to develop specific prevention strategies. The sporadic nature of most cases, occurring without clear hereditary patterns, makes it particularly difficult to identify preventive measures that might reduce risk.^[4]

However, maintaining overall brain health through general wellness practices makes good sense, even if their specific effect on preventing this particular form of dementia remains unclear. A healthy lifestyle that includes regular physical activity, a balanced diet, mental stimulation, social engagement, and management of cardiovascular risk factors like high blood pressure and diabetes may support brain health in general. These same practices that help maintain overall health might potentially contribute to reducing dementia risk, though no definitive evidence exists specifically for dementia with Lewy bodies.

For people with a family history of the condition or identified genetic risk factors, no specific screening programs or preventive treatments are currently available. Regular health check-ups and awareness of early symptoms remain the best approach for catching the disease in its earliest stages, when treatment and planning can begin promptly. Research continues to explore whether any interventions might delay or prevent the onset of this condition, but such discoveries remain in the future.^[4]

Pathophysiology

The pathophysiology of dementia with Lewy bodies centers on the accumulation of abnormal alpha-synuclein protein deposits throughout the brain. These protein clumps, called Lewy bodies, and their thread-like counterparts, Lewy neurites, represent the hallmark brain abnormality of the disease. The alpha-synuclein protein normally exists in the brain, but in this condition, it misfolds and aggregates into abnormal formations that collect inside neurons. These deposits fundamentally disrupt how brain cells function.^[3]

The protein deposits interfere with the production and regulation of important chemical messengers in the brain. One particularly affected chemical is acetylcholine, which plays a crucial role in memory, learning, and attention. Another affected system involves dopamine, a chemical messenger important for coordinating movement and emotional responses. When these chemical messaging systems become disrupted, the brain struggles to carry out its normal functions, leading to the cognitive, movement, and behavioral symptoms that characterize the disease.^[1]

The Lewy body deposits don’t accumulate in just one area of the brain—they spread throughout multiple brain regions. They particularly affect areas involved in thinking, memory, visual perception, and movement control. This widespread distribution explains why the disease creates such varied symptoms affecting so many different functions. The deposits also affect the brainstem, a region that controls many automatic body functions, which accounts for the autonomic symptoms like blood pressure problems, digestive issues, and temperature regulation difficulties.^[7]

As the disease progresses, more and more neurons become affected by the protein deposits and eventually die. This gradual loss of brain cells leads to the progressive worsening of symptoms over time. The damage occurs in both the central nervous system (the brain and spinal cord) and the autonomic nervous system (which controls automatic body functions). In fact, the protein deposits can be found throughout the body, affecting nerve cells in the heart and gastrointestinal tract, which explains why symptoms extend beyond just the brain to affect digestion, heart function, and virtually every level of gut function from chewing to elimination.^[8]

Interestingly, Lewy body deposits also appear in other conditions, particularly Parkinson’s disease. They can even be found in some cases of Alzheimer’s disease. This overlap in the underlying pathology helps explain why these conditions can have overlapping symptoms and why distinguishing between them can be challenging. The distribution and timing of when these deposits appear in different brain regions determines whether someone develops dementia with Lewy bodies, Parkinson’s disease dementia, or another related condition.^[3]