Adherence to the Japanese Diet is Associated with Lower Risk of Geriatric Depression: A Prospective-Cohort Study Based on the New Integrated Suburban Seniority Investigation (NISSIN) Project.

OBJECTIVES: Geriatric depression is an increasingly important public health issue in an aging society. However, while Japan boasts one of the world's highest and healthiest life expectancies at birth, there was no prospective cohort study dedicated to the specific association between the Japanese diet and geriatric depression. Thus, we aimed to examine this relationship and assess whether such association extends beyond better physical health secondary to higher diet quality. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS: Our study utilized the New Integrated Suburban Seniority Investigation (NISSIN) Project, which is an age-specific prospective cohort study that recruited residents of Nisshin City, Japan who were about to reach 65 years of age between 1996 and 2005. We measured the adherence to the Japanese diet of 1620 elderly Japanese individuals (827 male and 793 female) with a modified version of the Japanese Diet Index (JDI) and assessed the development of geriatric depression with the Geriatric Depression Scale 15 items questionnaire when they reached 70 years of age. RESULTS: A total of 135 individuals developed geriatric depression at 70 years of age. After adjusting for major confounding factors, those within the highest group of adherence to the Japanese diet had significantly reduced risk of developing geriatric depression (adjusted odds ratio [aOR] = 0.525, 95% confidence interval [CI]: 0.286 - 0.962) when compared to those with the lowest adherence, and each point received on the JDI was also associated with reduced risk of geriatric depression (aOR = 0.900, 95% CI: 0.816-0.992). Dietary item-wise analyses showed that fish and shellfish (p = 0.024), green-yellow vegetable (p = 0.003), and soybean-derived products (p = 0.001) were significantly associated with lower risk of geriatric depression. CONCLUSION: Adherence to the Japanese diet, especially those rich in green-yellow vegetables, soybean-derived products, and fish and shellfish, may be protective against geriatric depression.