Seven healthy habits and lifestyle factors may play a role in reducing the risk of dementia in people at highest genetic risk, according to a study published in the online edition of the American Academy of Neurology medical journal Neurology.

The seven factors for cardiovascular and brain health, known as the American Heart Association's include: being active, eating well, losing weight, not smoking, maintaining normal blood pressure, controlling cholesterol, and lowering blood sugar.

The study involved 8,823 people with European roots and 2,738 people with African roots, who were followed for 30 years.

The average age of people at the beginning of the study was 54 years. Study participants reported their scores on all seven health factors. The total scores ranged from 0 to 14, with 0 being the most unhealthy score and 14 being the healthiest.

The median score for people with European ancestry was 8.3, and the median score for people with African ancestry was 6.6.

The researchers calculated genetic risk scores at the start of the study using Alzheimer's genomic statistics, which were used to study the genetic risk for dementia. Participants with European ancestry were divided into five groups, and participants with African ancestry were divided into three groups based on genetic risk scores.

The group with the highest genetic risk included people who had at least one copy of the APOE gene variant associated with Alzheimer's disease, APOE e4.

Among people with European roots, 27.9% had the APOE e4 variant, and among those with African roots, 40.4% had the APOE e4 variant. The lowest risk group had the APOE e2 variant, which was associated with a reduced risk of dementia. By the end of the study, 1,603 people of European descent had developed dementia, while 631 people of African ancestry had dementia.

The researchers found that people of European ancestry who scored highest on lifestyle factors had a lower risk of developing dementia in all five genetic risk groups, including the group with the highest genetic risk for developing dementia.

For every one point increase in the assessment of a lifestyle factor, the risk of developing dementia was reduced by 9%. Among people of European ancestry, compared with the low category of the lifestyle factor score, the intermediate and high categories were associated with a 30% and 43% reduction in the risk of developing dementia, respectively.

Among people of African ancestry, intermediate and high categories were associated with 6% and 17% reduced risk of dementia, respectively. Among people of African ancestry, the researchers found a similar pattern of dementia risk reduction in all three groups among those who scored higher on lifestyle factors.