Diet in midlife not effective for dementia prevention

A high-quality diet in midlife may not be effective for long-term dementia prevention, according to a new study published in the Journal of the American Medical Association.

 In a prospective cohort study of 8,225 participants with an average age of 50 years old, diet quality was assessed through nearly 25 years of follow-up using food frequency questionnaires and the Alternate Health Eating Index (AHEI), a diet quality score with higher scores indicating a healthier diet, according to the study abstract.

The study relied on self-reported food frequency questionnaires. The AEHI diet score is based on 11 components, six of which the highest intake is considered ideal: vegetables, fruits, whole grains, nuts and legumes, long-chain omega-3 fatty acids, and polyunsaturated fatty acids; and four of which the lowest intake or avoidance is considered ideal: sugar-sweetened drinks and fruit juice, red and processed meat, trans fat, and sodium. Moderate alcohol consumption was considered ideal as well.

Based on the diet scores, participants were divided in two three categories of diet quality, worst, intermediate, and best. Physical activity, type 2 diabetes, and dyslipidemia did not vary between the diet quality groups, the study said.  

Researchers found 344 people developed dementia, with no significant different in incidence rate across scores. But despite lack of significant association, researchers say the findings do suggest a slight decrease in diet quality in the years preceding dementia, consistent with other studies that say diet is a feature of preclinical dementia. This could be the basis for future research, the researchers said.