AimTo clarify the effectiveness of dietary diversity, calculated by dietary records, on cognitive decline.MethodsData were derived from the National Institute for Longevity Sciences - Longitudinal Study of Aging. Participants comprised 298 men and 272 women aged 60-81years at baseline (second wave) who participated in the follow-up study (third to seventh wave) at least once. Cognitive function was assessed with the Mini-Mental State Examination in all study waves. Dietary diversity was determined using the Quantitative Index for Dietary Diversity based on a 3-day dietary record in the second wave. Cumulative data among participants with a Mini-Mental State Examination score >27 in the second wave were analyzed using a generalized estimating equation. Multivariate adjusted odds ratios and 95% confidence intervals for Mini-Mental State Examination scores 27 in each study wave according to a 1 standard deviation (increase), or quartiles of the Quantitative Index for Dietary Diversity at baseline, were adjusted for sex, age, follow-up time, baseline Mini-Mental State Examination score, education, body mass index, annual household income, current smoking status, energy intake and disease history.ResultsMultivariate adjusted odds ratio for a decline in Mini-Mental State Examination score was 0.79 (95% CI 0.70-0.89; P<0.001) with a 1 SD increase in dietary diversity score, or 1.00 (reference), 0.99 (95% CI 0.70-1.43), 0.68 (95% CI 0.46-0.99) and 0.56 (95% CI 0.38-0.83) according to the lowest through highest quartiles of dietary diversity score, respectively (trend P=0.001).ConclusionsDaily intake of various kinds of food might be a protective factor against cognitive decline in community-dwelling Japanese older adults. Geriatr Gerontol Int 2017; 17: 937-944.