Difference Between Alzheimer's and Lewy Body Dementia

Alzheimer’s disease and Lewy body dementia are two types of dementia. There are several similarities but also some clear differences between the two progressive neurological (nervous system-related) disorders.

This article takes a look at how Lewy body dementia differs from Alzheimer's disease. It also compares the causes, symptoms, and prognosis (expected outcome) for each of the conditions and outlines the different risk factors and treatments.

Lewy Body Dementia vs. Alzheimer's Disease

Lewy body dementia and Alzheimer's disease are similar but not the same. This starts with how the features of dementia differ for each disorder:

• Lewy body dementia (LBD) is a form of dementia with characteristics of Parkinson's disease that affects executive function (problem-solving), speed of thinking, memory, movement, and moods. LBD can cause visual hallucinations, problems with attention and alertness, and movement problems such as tremors and stiffness.
• Alzheimer's disease is the more common form of dementia that primarily affects language, behavior, and memory. It mainly manifests with profound memory loss, such as trouble recalling events, recognizing people, naming objects, or learning new information.

LBD and Alzheimer's disease can appear similar in the early stages, and it is not uncommon for someone with LBD to be mistakenly diagnosed with Alzheimer's at first.

The underlying causes of Alzheimer's and LBD can and often do overlap. As a result, a person with LBD might experience Alzheimer-type changes in their brain, resulting in shared characteristics and symptoms referred to as mixed dementia.

The main differences between LBD and Alzheimer's can be summarized in the following chart:

Prevalence

Lewy body dementia is the second most common type of dementia, with an estimated 1.4 million living with LBD in the United States. It is thought to be slightly more common in males than females. Because LBD is thought to be underdiagnosed, the actual number of people with the disease may be higher.

Alzheimer's disease is the most common type of dementia. As many as 5.8 million people in the United States are living with this progressive neurodegenerative disorder. Females are more affected than males but tend to live longer. Around 5% of adults ages 60 to 74 have Alzheimer's increasing to 14% in those 75 to 84.

Causes of Lewy Body Dementia vs. Alzheimer's

Lewy body dementia is caused by the abnormal buildup of proteins, called Lewy bodies, in the brain. When clumps of these proteins accumulate, nerves in the brain start to lose their function and eventually die. The damage in the brain is widespread and affects many domains of thinking and functioning.

Alzheimer's is caused by the abnormal buildup of proteins called amyloid that leads to the formation of plaques in the brain. The abnormal twisting of another protein called tau causes neurofibrillary tangles that block signals between nerve cells. Over time, the progressive damage will kill the cells.

Risk Factors

LBD and Alzheimer's share many of the same risk factors but have some of their own as well. While less is known about LBD, there are five risk factors noted in a 2013 study published in Neurology.

Symptoms

Lewy body dementia and Alzheimer's disease have both similarities and differences in their symptoms. Here is how the two compare:

Loss of Cognition and Memory

Cognition is the mental process of acquiring knowledge and understanding through thought, experience, and the senses. With both LBD and Alzheimer's, cognition is affected but in significantly different ways.

With LBD, the loss of cognition and memory can fluctuate. On one day, a person will LBD will not recognize a grandchild but, on the next, be able to recall the names of each of their grandchildren.

With Alzheimer's, there may be variations, but the decline is generally steady, and there is not usually a big change from one day to the next. Over time, the gaps in lucidity become smaller and smaller.

Physical Movement

One of the early symptoms of LBD is difficulty walking and decreased balance and ability to control movements. These symptoms are similar to Parkinson’s disease. Frequent falling is also common early in the disease.

With Alzheimer's, physical deterioration usually does not occur until the disease is advanced. With that said, because Alzheimer's typically affects older people, falling can occur due to frailty and the loss of orientation.

Some people with LBD display a flat affect, wherein their faces show very little emotion. This is another symptom present early in LBD and overlaps with Parkinson’s. While facial expressions often decrease with Alzheimer's, this usually doesn’t until the later stages.

Sleep Disturbances and Visual Hallucinations

People with LBD sometimes experience a condition known as REM sleep behavior disorder in which they will physically act out situations in their dreams. Some research suggests that REM sleep behavior disorder is an earlier predictor of LBD.

Another common LBD symptom is visual hallucinations, wherein people will see things that aren’t there. These hallucinations typically occur earlier in the course of LBD.

Hallucinations do occur with Alzheimer’s but are not as common. They also tend to occur in the later stages of the disease.

Similarly, REM sleep behavior disorder is not characteristic of Alzheimer's, although other types of sleep disturbances can occur.

Sensitivity to Antipsychotics

People with LBD have a high risk of serious side effects from antipsychotic medications. These are sometimes used as a last resort for people with behavioral symptoms of Alzheimer's. Doing so with LBD can lead to a potentially life-threatening condition called neuroleptic malignant syndrome (NMS).

Symptoms of NMS include:

• High fever
• Muscle stiffness
• Changes in mental state
• Irregular heartbeat
• Excessive sweating
• Swings in blood pressure

By contrast, people with Alzheimer's have only a small risk of developing NSM.

Treatment

Where LBD and Alzheimer's vary significantly is in the ways they are treated. While some drugs, like cholinesterase inhibitors, can be used for both disorders, there are others that have proven to slow progression with Alzheimer's only.

Lewy Body Dementia

There is no cure for LBD. Some symptoms can be managed with a treatment plan that may include medications, physical therapy, and counseling. The plan may also involve improving home safety and the everyday quality of life.

A combination of drugs called carbidopa-levodopa may be prescribed to improve LBD-related mobility problems, although they will not reverse symptoms.

Klonopin (clonazepam) may be prescribed to reduce symptoms of REM sleep behavior disorder, while melatonin can be taken to reduce insomnia.

Cholinesterase inhibitors are a class of drugs that may help treat some of the cognitive and behavioral symptoms of LBD and Alzheimer's, including impaired memory and awareness. Options include Razadyne (galantamine), Exelon (rivastigmine), and Aricept (donepezil).

Alzheimer's Disease

In addition to cholinesterase inhibitors, another class of drugs called N-methyl D-aspartate (NMDA) antagonists may be prescribed to help slow the progression of Alzheimer's. This includes the drug Namenda (memantine).

People with Alzheimer's can also benefit from physical therapy to help them stay mobile and improve their ability to perform daily tasks for as long as possible.

Prognosis

By and large, the prognosis of LBD is less favorable than Alzheimer's.

According to a 2019 study in PLoS One, the median life expectancy of people with LBD is between three and five years after the appearance of symptoms. This is far less than expected in people with Parkinson's, although outcomes can vary. Death is often the result of respiratory failure due to damage to the part of the brain that regulates breathing.

By contrast, people with Alzheimer's survive for between four and 10 years after they are diagnosed. Improved Alzheimer's treatments account for part of the disparity, but it is likely that LBD is simply a more aggressive disorder. The main cause of death from Alzheimer's is secondary infections like pneumonia.

Summary

Lewy body dementia (LBD) and Alzheimer's disease are the two most common forms of dementia that differ in a number of key ways. Both are linked to the abnormal buildup of proteins in the brains, but those involved with LBD are Lewy bodies and those involved with Alzheimer's are amyloids.

LBD also tends to progress faster and affects many different mental and physical domains, including thought, behavior, alertness, awareness, sleep, moods, and movement. Alzheimer's progresses somewhat slower and mainly affects memory, behavior, awareness, and language.

Because the causes and risk factors differ, the treatment of LBD and Alzheimer's also vary. Even so, LBD is frequently mistaken for Alzheimer's and, as such may be treated inappropriately.

A Word From Verywell

Understanding the differences between Lewy body dementia and Alzheimer's disease can help you distinguish between the two and elaborate on symptoms you or a loved one may be experiencing. In this way, you can be better ensured of an accurate diagnosis and appropriate treatment.

You can also help friends and family understand how Lewy body dementia is similar to—and different from—Alzheimer's disease. In this way, they can get a better grasp of the diagnosis and what to expect as caregivers.