Long-term association of vegetable and fruit intake with risk of dementia in Japanese older adults: the Hisayama study

BACKGROUND: Several prospective Western studies have reported an inverse association of vegetable and fruit intake with dementia risk. However, there is limited epidemiologic evidence in Asians. This study investigated the association of intakes of vegetables, fruits, and their nutrients on the risk of incident dementia and its subtypes in a Japanese community. METHODS: A total of 1071 participants (452 men and 619 women) aged ≥60 years without dementia at baseline were prospectively followed up for 24 years. Intakes of vegetables, fruits, and nutrients were evaluated using a 70-item semiquantitative food frequency questionnaire at baseline and were categorized into quartiles separately by gender. The outcome measure was the development of dementia and its subtypes—namely, Alzheimer’s disease (AD) and vascular dementia (VaD). The risk estimates of incident dementia were computed using a Cox proportional hazards model. RESULTS: During the long-term follow-up period, 464 subjects developed dementia, of whom 286 had AD and 144 had VaD. Higher vegetable intake was associated gradually with lower risk of developing dementia and AD (both P-trend < 0.05), but not VaD, after adjusting for confounders. Subjects allocated the highest quartile of vegetable intake had 27 and 31% lower risk of dementia and AD, respectively, than those with the lowest quartile. The risk of dementia decreased significantly with higher intakes of vitamin A, riboflavin, vitamin C, magnesium, calcium, and potassium (all P-trend < 0.05). Subjects with higher total dietary fiber intake tended to be at decreased risk for total dementia (P-trend = 0.07). Meanwhile, there were no significant associations between fruit intake and the risk of dementia and its subtypes. CONCLUSION: Higher intakes of vegetables and their constituent nutrients were associated with a lower risk of dementia in Japanese older adults. A diet rich in vegetables may be beneficial in reducing the dementia risk in Asians. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12877-022-02939-2.