As the population ages, diseases like dementia are in the spotlight more than ever. Many people might wonder what causes dementia and what their own risk factors are; currently, the answers to those questions are complicated.

Genetic And Lifestyle Risk Factors

The short answer is that the risk of developing dementia is related to a combination of genetics and lifestyle, with age being the biggest risk factor.

In most cases, genetic risk factors come from small influences of many genes, rather than one mutation being responsible for the entire genetic effect. Therefore, it is unlikely that a child will inherit every dementia-related mutation that a parent has.

Dementia-Related Diseases

However, dementia is really a catchall term for different diseases and conditions that all cause (mostly short-term) memory loss, mood changes and communication problems, as well as other related symptoms.

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Different types of dementia have different primary causes, with the more rare types more likely to be caused by genetics. To understand your specific risk factors, it's important to understand these different types of dementia and their known causes. Here are the three most common forms:

Alzheimer's Disease

There are two types of Alzheimer's disease: Early onset and late onset. Late onset Alzheimer's is the most common form of dementia, but researchers are not yet sure what causes it; most likely, there are a combination of genetic, lifestyle and environmental factors that contribute to the disease.

Recent research has pinpointed a gene on chromosome 19 that has instructions for making a protein that helps carry cholesterol through the bloodstream as a strong risk-factor gene, but much more research is necessary to understand exactly how it works.

Early onset Alzheimer's, on the other hand, affects less than 5 percent of Alzheimer's patients, and most cases are familial Alzheimer's disease, an inherited form.

Unlike the mutations associated with late onset Alzheimer's, scientists have identified three single-gene mutations that directly cause early onset Alzheimer's. Usually, these genes affect multiple members of several generations of families with familial Alzheimer's disease.

Vascular Dementia

Vascular dementia is the second most common form of dementia. It occurs as a result of minor strokes, or other conditions that damage smaller blood vessels in the brain.

Because of this, any genetic risk factors for vascular dementia are not risk factors for dementia itself; but rather for raised blood pressure, stroke and other conditions that affect the heart and blood vessels.

Dementia With Lewy Bodies

Lewy bodies are deposits of a particular type of protein that build up in the brain and damage cells. They can sometimes be found in the brains of people with other types of dementia, such as Parkinson's disease dementia and Alzheimer's.

The cause of dementia with Lewy bodies is unknown, but the overlaps with Parkinson's and Alzheimer's suggest there could be a genetic link between different types of dementia. However, familial cases of dementia with Lewy bodies are very rare.

Minimizing The Risk

For most people, there is no way of knowing whether or not you have genetic risk factors for dementia.

Except in rare cases, environment and lifestyle play a large role, if not larger than genetics, in determining dementia risk.

Physical activity and a healthy diet can both help lower your risk of dementia, as can keeping mentally “fit," by doing activities such as crossword puzzles, playing cards or reading.

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