Alzheimer’s disease risk is known to involve both genetics and lifestyle choices. We can actively choose to eat well and exercise, but we do not have control over our genes. Therefore, it is important to understand the relationship between these two types of risk factors and determine if a healthy lifestyle can reduce dementia risk regardless of one’s genetic risk.
A recent study examining 196,383 people over age 60 of European descent from the UK Biobank study offers some insight into this question [1]. Enrolled participants were scored for genetic risk and lifestyle risk and were followed for an average of eight years to see which people developed dementia. The researchers could then determine if people with healthier lifestyles were less likely to develop dementia, and whether genetic risk influenced this association.
The risk score for each person was calculated based on the presence or absence of thousands of genetic variants previously shown to be associated with Alzheimer’s disease risk. It is important to note that the risk gene variants were discovered from large genetic studies of people from European ancestry, thus these study results may only apply to people of similar ancestry.
The healthy lifestyle score consisted of four lifestyle choices known to play a role in Alzheimer’s disease risk: smoking, diet, physical activity, and alcohol consumption. A healthy lifestyle was defined as being a non-smoker, meeting the American Heart Association guidelines for regular physical activity [2], eating a healthy diet containing at least four food groups associated with heart health (High: fruits, vegetables, fish, whole grains; Low: processed meats, red meats, refined grains), and moderate alcohol consumption based on US dietary guidelines (up to one drink per day for women and up to two for men) [3]. It should be noted that that the lifestyle score was based on self-reported questionnaires, and not based on objective measures.
The study found that a high genetic risk and unhealthy lifestyle were each independently associated with a higher risk for dementia, such that the risk associated with genes and the risk associated with lifestyle add together to determine total dementia risk. People with the highest genetic risk were 1.9 times more likely to develop dementia, compared to those with low genetic risk. An unhealthy lifestyle was associated with 1.4 times higher dementia risk relative to a healthy lifestyle, while those with both high genetic risk and an unhealthy lifestyle had 2.8 times higher risk. The combined risk was found to be higher in women, such that women with high genetic risk and an unhealthy lifestyle had 4 times higher dementia risk compared to women with low genetic risk and a healthy lifestyle.
These findings mean that unhealthy lifestyle choices can increase one’s chance of developing dementia whether or not one is at high genetic risk. Genetics and lifestyle factors can be considered as separate sources of risk that together make up one’s overall dementia risk. While people with high genetic risk will still have a higher risk of dementia than those with low genetic risk, everyone can reduce the lifestyle component of risk by making healthy choices, such as taking the seven steps to protect your cognitive vitality.
Betsy Mills, PhD, is a member of the ADDF's Aging and Alzheimer's Prevention program. She critically evaluates the scientific evidence regarding prospective therapies to promote brain health and/or prevent Alzheimer's disease, and contributes to CognitiveVitality.org. Dr. Mills came to the ADDF from the University of Michigan, where she served as the grant writing manager for a clinical laboratory specializing in neuroautoimmune diseases. She also completed a Postdoctoral fellowship at the University of Michigan, where she worked to uncover genes that could promote retina regeneration. She earned her doctorate in neuroscience at Johns Hopkins University School of Medicine, where she studied the role of glial cells in the optic nerve, and their contribution to neurodegeneration in glaucoma. She obtained her bachelor's degree in biology from the College of the Holy Cross. Dr. Mills has a strong passion for community outreach, and has served as program presenter with the Michigan Great Lakes Chapter of the Alzheimer's Association to promote dementia awareness.
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