The precise cause of Lewy body dementia remains unknown. Lewy body dementia (LBD) involves abnormal deposits of alpha-synuclein, a brain protein, but researchers cannot yet explain why these deposits form in most people. The deposits damage brain cells involved in thinking, movement, mood, sleep, and smell. Age is the strongest established risk factor, while certain symptoms, genes, and family history can indicate higher risk without making LBD inevitable.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- How Lewy bodies damage brain cells
- Which parts of the brain are affected?
- Who has a higher risk?
- How much do genes and family history matter?
- What should someone do with these risk clues?
How Lewy bodies damage brain cells
Alpha-synuclein normally exists within neurons, or nerve cells. In LBD, the protein clumps into deposits called lewy bodies. These deposits interfere with cell function and eventually contribute to neuron death and widespread brain damage, according to the National Institute on Aging.
Researchers understand this damaging process better than its starting point. They do not yet know what triggers alpha-synuclein to clump in most affected people. That distinction matters. Lewy bodies help explain how LBD harms the brain, but their presence does not identify one universal external, behavioral, or genetic cause.
Which parts of the brain are affected?
Lewy-body-related damage can reach several connected brain regions. These include the cortex, limbic system, hippocampus, midbrain and basal ganglia, brainstem, and pathways involved in smell.
The affected regions help explain LBD's varied symptoms: LBD also causes losses among neurons that use acetylcholine and dopamine. Acetylcholine supports cognition, memory, and learning, while dopamine is important for movement, mood, motivation, and sleep. Damage across both systems helps explain why LBD can affect several abilities at once.
- Cortex and hippocampus damage relates to problems with cognition, memory, and learning.
- Limbic system changes relate to emotion, behavior, and motivation.
- Midbrain and basal ganglia damage relates to movement problems.
- Brainstem damage relates to sleep and other automatic functions.
- Damage along smell pathways relates to reduced smell.
Who has a higher risk?
Age is the greatest established risk factor. Most people with LBD develop it after age 50, and the condition affects more men than women, according to the National Institute on Aging. REM sleep behavior disorder is also linked with higher LBD risk.
A person with this disorder physically acts out dreams during rapid eye movement sleep, and it can appear years before other symptoms of dementia with Lewy bodies. Loss of smell is another feature associated with higher risk. These associations do not mean that either symptom confirms LBD. They are reasons to consider the full pattern of cognitive, movement, sleep, mood, and smell changes rather than treating one feature as proof.
How much do genes and family history matter?
LBD is usually not hereditary, although having an affected family member can raise a person's risk. Rare variants in the SNCA and SNCB genes can directly cause dementia with Lewy bodies. Other variants change probability rather than determine the outcome.
GBA1 variants and the APOE ε4 form raise risk, but some people who carry them never develop the disease, according to MedlinePlus Genetics. This difference is important when considering genetic information. A risk variant is not a diagnosis or a prediction, and there is currently no genetic test that can accurately determine who will develop LBD.
What should someone do with these risk clues?
Look for patterns and timing rather than trying to identify one cause. A useful record for a medical appointment may include: No single clinical scan or test can definitively diagnose LBD during life, according to the National Institute on Aging. A detailed symptom timeline can therefore help a clinician assess the overall pattern and consider other explanations.
- When thinking, attention, movement, sleep, mood, or smell changes began
- Whether symptoms fluctuate or occur together
- Any dream-enacting behavior during sleep
- A family history of LBD or related neurological problems
- Current medicines and noticeable changes in daily function
