Dietary intake of folate, vitamin B6, vitamin B12, and riboflavin and the risk of incident dementia.

Background/objectives: Low intake of B vitamins may increase dementia; However, epidemiological evidence, particularly for riboflavin (vitamin B₂), remains sparse. This study aimed to examine the association between dietary intakes of B vitamins (riboflavin, vitamin B₆, vitamin B₁₂, and folate) and the incidence of disabling dementia necessitating care under Japan's national insurance over a 15-year observation period.

Methods: As part of the Circulatory Risk in Communities Study, a prospective study involving a community-based cohort of 4171 Japanese individuals aged 40-69 years was conducted. Dietary intakes of B vitamins were estimated through a single 24-h dietary recall method. Disabling dementia was defined by the daily living disability status related to dementia based on the long-term care insurance system of Japan. Hazard ratios of disabling dementia were estimated using area-stratified Cox proportional hazard models.

Results: Over a median follow-up of 15.4 years, 887 cases of disabling dementia were identified. Riboflavin intake was inversely associated with the risk of disabling dementia; the multivariable hazard ratio for the highest versus lowest quartiles was 0.51 (95% CI 0.42-0.63; P for trend <0.001). A similar inverse association was observed for vitamin B₆ and folate intakes, with multivariable hazard ratios of 0.80 (0.66-0.97; P for trend = 0.01) and 0.79 (0.65-0.96; P for trend <0.001), respectively.

Conclusions: Our findings suggest that dietary intake of B vitamins, especially riboflavin, vitamin B₆, and folate, is associated with a reduced risk of disabling dementia in Japanese individuals.