“The good news is that people who are at the highest genetic risk are likely to have a lower risk of dementia from living the same healthy lifestyle.”
The study looked at 8,823 people of European descent and 2,738 people of African descent who were followed for 30 years. The average age of the people at the start of the study was 54 years.
Study participants reported their levels in all seven health factors. The total scores ranged from 0 to 14, with 0 representing the most unhealthy score and 14 representing the healthiest score. Those with European ancestry had an average score of 8.3 and those with African ancestry had a mean score of 6.6.
Researchers calculated genetic risk scores at the start of the study using genome-wide data from Alzheimer’s disease, which has been used to study the genetic risk of dementia.
Participants of European ancestry were divided into five groups and those of African ancestry into three groups based on genetic risk scores. The group at highest genetic risk included those who had at least one copy of the APOE gene variant associated with Alzheimer’s disease, APOE E4.
Of those of European descent, 27.9% had the APOE e4 variant, while 40.4% of those of African descent had the APOE e4 variant. The lowest-risk group had the APOE e2 variant, which is associated with a lower risk of dementia.
By the end of the study, 1,603 people of European ancestry developed dementia and 631 people of African ancestry developed dementia.
For people of European ancestry, the researchers found that those with the highest scores in lifestyle factors had a lower risk of dementia in all five genetic risk groups, including the group with the highest genetic risk of dementia.
For each one-point increase in the lifestyle factor score, there was a 9% lower risk of developing dementia.
In people of European ancestry, the intermediate and high ranges were associated with a 30% and 43% lower risk for dementia, respectively, compared with a low range of lifestyle factor scores.
Among people of African descent, the intermediate and upper categories were associated with a 6% and 17% lower risk for dementia, respectively.
Among people of African descent, the researchers found a similar pattern of reduced dementia risk in all three groups with higher scores on lifestyle factors. But the researchers said the small number of participants in this group limited the findings, so more research is needed.
“Large sample sizes from different populations are needed to obtain more reliable estimates of the effects of these modifiable health factors on dementia risk within different genetic risk groups and paternal backgrounds,” Tin said.
A limitation of the study was the small sample size among people of African ancestry and the many African American participants recruited from one location.
The study was supported by the National Heart, Lung and Blood Institute, the National Institutes of Health, the Department of Health and Human Services, and the National Human Genome Research Institute.