When someone you love is diagnosed with Lewy body dementia (LBD), one of the first questions you ask is why. What caused this? Could it have been prevented? The honest answer is that scientists don’t fully understand why some people develop LBD, and others don’t. But research has identified what happens in the brain and which factors increase risk.

Key Takeaways

• LBD is caused by abnormal protein deposits called Lewy bodies that build up in brain cells and disrupt normal function
• The exact trigger for Lewy body formation remains unknown in most cases
• Age is the strongest risk factor, with most cases occurring after age 50
• Men are more likely to develop LBD than women
• Having a family member with LBD or Parkinson’s disease slightly increases risk, but LBD is not typically inherited
• REM sleep behavior disorder and loss of smell are early warning signs linked to higher LBD risk
• There is currently no proven way to prevent LBD

What Causes Lewy Bodies to Form in the Brain

LBD occurs when a protein called alpha-synuclein misfolds and clumps together inside brain cells. These abnormal protein deposits are called Lewy bodies, named after the neurologist who first described them in 1912. Under a microscope, they appear as round masses inside neurons.

In a healthy brain, alpha-synuclein plays a role in communication between nerve cells. But when this protein misfolds, it begins to stick together and form clumps. These clumps damage the neurons that house them, disrupting the brain’s chemical messengers. Two messengers are particularly affected: acetylcholine, which is important for memory and learning, and dopamine, which affects movement, mood, and thinking.

The location of Lewy bodies in the brain determines which symptoms appear. When they accumulate in areas controlling thinking and memory, cognitive symptoms develop. When they form in regions controlling movement, Parkinson-like symptoms emerge. In LBD, Lewy bodies spread throughout the brain, which is why the disease affects so many different functions.

Scientists still don’t know what triggers alpha-synuclein to start misfolding in the first place. Research suggests the abnormal proteins may spread from cell to cell in a chain reaction, but what initiates that process remains one of the central mysteries of the disease.

Risk Factors for Lewy Body Dementia

While researchers can’t point to a single cause, several factors are associated with a higher risk of developing LBD.

Age is the strongest known risk factor. LBD primarily affects people over 50, and risk increases with age. The disease is rare in younger adults.

Sex plays a role. Statistically, men are diagnosed with LBD more often than women, though researchers aren’t certain why. Theories include differences in hormone exposure, genetic factors, or occupational exposures to toxins.

Family history has some influence. Having a close relative with LBD or Parkinson’s disease modestly increases risk. However, LBD is not typically considered a hereditary disease. Most people who develop it have no family history.

Genetics contribute in some cases. Certain gene variants, including APOE (also linked to Alzheimer’s) and GBA, are associated with increased LBD risk. But having these genes doesn’t mean someone will definitely develop the disease, and most people with LBD don’t have identifiable genetic causes.

REM sleep behavior disorder is strongly linked to future LBD. People with this condition physically act out their dreams during sleep. Research shows that many people diagnosed with REM sleep behavior disorder eventually develop LBD or Parkinson’s disease, sometimes decades later. This suggests the disease process may begin long before other symptoms appear.

Loss of smell is another early warning sign associated with a higher risk. Reduced ability to detect odors often appears years before cognitive or movement symptoms.

Can Lifestyle or Environment Cause Lewy Body Dementia?

Researchers are actively studying whether environmental factors contribute to LBD. Some early research suggests possible links to air pollution, certain metals, and some infections. Coffee consumption and the Mediterranean diet may have protective effects. However, none of these findings are definitive enough to guide prevention strategies.

Unlike heart disease or type 2 diabetes, there are no proven lifestyle changes that prevent LBD. That said, what’s good for overall brain health may help. Regular exercise, mental stimulation, social connection, and managing cardiovascular risk factors like high blood pressure and diabetes are reasonable approaches, even without specific evidence for LBD prevention.

Why Your Loved One?

If you’re looking for answers about why this happened to someone you love, you may not find a satisfying explanation. In most cases, there’s no identifiable cause. Your loved one didn’t do anything wrong. They couldn’t have prevented this.

What matters now is understanding the disease so you can provide the best possible care and support. For more information about how LBD progresses and what to expect, see our complete guide to Lewy body dementia.

Our helpline is available every day of the year from 8am to 8pm Eastern time at 516-218-2026 or 833-LBDLINE. You can also reach us by email at norma@lbdny.org.

Frequently Asked Questions

Is Lewy body dementia hereditary? Usually not. While having a family member with LBD or Parkinson’s slightly increases risk, most people with LBD have no family history. Only a small percentage of cases are linked to specific genetic variants.

Can Lewy body dementia be prevented? There is currently no proven way to prevent LBD. Maintaining overall brain health through exercise, mental activity, and managing cardiovascular risk factors is reasonable but not specifically proven to prevent this disease.

Can a virus or infection cause Lewy body dementia? Some research suggests certain infections may be associated with increased risk, but no specific virus or bacteria has been proven to cause LBD. This is an active area of study.

Does head injury cause Lewy body dementia? Traumatic brain injury has been associated with increased risk of various dementias, but a direct causal link to LBD hasn’t been established.

Why do more men get LBD than women? Researchers aren’t sure. Possible explanations include differences in occupational exposures, hormonal factors, or genetic susceptibility, but none have been confirmed.