Polyunsaturated fatty acids, fish intake and risk of disabling dementia in Japan: the JPHC Disabling Dementia Study.

Abstract

Objective: The aim of this study was to assess the association between fish intake, n-3 polyunsaturated fatty acids (PUFA), n-6 PUFA and risk of disabling dementia.

Design: Prospective cohort.

Setting: Municipalities within the Japan Public Health Center-based Prospective Study.

Participants: 43,651 participants: (20,002 men and 23,649 women).

Results: Exposure intake of fish, n-3 and n-6 PUFA intake were evaluated in 1995-1997. We defined disabling dementia cases as participants who were certified to receive disability care under the long-term-care insurance program (2006-2016) in participating municipalities with a grade of activities of daily living related to dementia ≥IIa on the dementia rating scale (range 0-IV and M). Cox proportional hazard models were applied to obtain hazard ratios (HR) and 95% confidence intervals (CI) according to quartiles of exposures of interest. In the main analysis, we adjusted for age and area, smoking, body mass index, alcohol, and metabolic equivalent tasks. During 410,350 person years of follow-up with an average follow-up of 9.4 years, 5,278 cases of disabling dementia were diagnosed. Fish intake and most PUFAs were not associated with the risk of disabling dementia in men. In women, n-6 PUFA showed a significant decreasing trend in risk the highest HR (95% CI) compared with the lowest was 0.90 (0.81-0.99) (p for trend=0.024) and alpha-linolenic acid (ALA) was 0.91 (0.82 to 1.00) (p for trend=0.043).

Conclusions: Our findings suggest no association with fish in general and only n-6 PUFA and ALA may be associated with a decreased risk of disabling dementia especially in women.