Both genetic and lifestyle factors contribute to a person's risk of developing Alzheimer's disease and other types of dementia. Researchers conducted a retrospective study to determine if the genetic risk of dementia can be offset by lifestyle factors.

They used data from a population-based cohort of people ages 60 and older who had not self-reported or been diagnosed with cognitive decline or dementia at baseline. The researchers constructed a polygenic risk score based on genetic variants associated with a person's risk of Alzheimer's disease and dementia. They also created a healthy lifestyle score based on four well-established dementia risk factors: smoking status, physical activity, diet, and alcohol consumption. A total of 196,383 participants were followed for 1,545,433 person-years.

Of participants with high genetic risk, 1.23% developed dementia compared with 0.63% of those with low genetic risk. Of participants with an unfavorable lifestyle, 1.16% developed dementia compared with 0.82% of those with a favorable lifestyle. Of participants with both high genetic risk and an unfavorable lifestyle, 1.78% developed dementia compared with 0.56% of those with low genetic risk and a favorable lifestyle. A favorable lifestyle was associated with a lower risk of dementia across genetic groups. Among participants with high genetic risk, 1.13% with a favorable lifestyle developed dementia compared with 1.78% of those with an unfavorable lifestyle.

The study had several limitations, including that the lifestyle score wasn't independently validated, lifestyle factors were self-reported, and participants' mean age at the end of follow-up was 72 years, which limited the number of incident dementia cases.