This study examined the global association between the Traditional Japanese Diet Score and suicide rate.
Average food supply and energy supply by country were obtained from the Food and Agriculture Organization of the United Nations Statistics Division database (FAOSTAT). Traditional Japanese Diet Score (TJDS) was calculated from food group classifications. Age-standardized suicide rates per 100,000 people by country were obtained from the Global Burden of Disease 2017 database. The 26-year associations between TJDS and suicide rates were examined controlling for covariates using a mixed-effects model in 138 countries with populations of 1 million or greater.
A significant negative association was found in the analysis of the relationship between TJDS and the prevalence of suicide [β (se) = -0.126 (0.031), p < 0.001]. The interaction term between TJDS and year was also significant [β (se) = -0.011 (0.003), p < 0.001]. The change in the effect of TJDS on suicide rates by year was examined. The effect of TJDS was not significant from 1991 to 1999 but became significant after 2000; the slope of the TJDS to suicide rate in 2017 was -0.270 (95% confidence interval -0.382, -0.169, p < 0.001).
This was a national ecological study and did not consider individual differences in sex, age, and lifestyle.
TJDS may be is a protective factor for depression, which may prevent suicide. The association between TJDS and suicide rates became stronger over time and was inversely associated with suicide rates after 2000.

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