Dietary diversity and risk of late-life disabling dementia in middle-aged and older adults.

Background & Aims: A balanced diet integrating several foods and nutrients may promote the maintenance of brain function. Previous studies have substantiated the above hypothesis in the regional population in Japan. This study aimed to investigate the potential effect of dietary diversity on the risk of disabling dementia in a nationwide large-scale cohort of the Japanese population.

Methods: A total of 38,797 participants (17,708 men and 21,089 women) aged 45-74 years were followed up for a median of 11.0 years. The daily frequencies of the consumption of each of the 133 food and beverage items listed on a food frequency questionnaire (excluding five alcoholic beverages) were measured. The dietary diversity score was calculated as the number of food items consumed per day. Multivariable adjusted Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) of the dietary diversity score quintile groups.

Results: We documented 4302 participants with disabling dementia (11.1%) during the follow-up period. Among women, the dietary diversity score was inversely associated with disabling dementia (highest quintile HR [with the lowest quintile as the reference]: 0.67; 95% CI: 0.56-0.78; Q1-Q5 p for trend <0.001), but this was not true among men (highest quintile HR: 1.06; 95% CI: 0.87-1.29; Q1-Q5 p for trend = 0.415). These results did not change substantially when using disabling dementia with stroke as the outcome; the association remained significant among women but was absent among men.

Conclusions: Our findings indicate that eating a variety of foods may prevent disabling dementia only among women. Thus, the habit of consuming a variety of food items has important public health implications for women.