Association between Japanese balanced diet and frailty: the modifying effects of social connections in Japanese older adults

While the Japanese balanced die is a nutritional-related effort recommended in Japan’s health promotion policies, evidence about its association with frailty is scarce. It’s also worth noting the role of social context, given its wide associations with dietary behaviors and frailty. The present study examined the association between an unbalanced diet and frailty, and whether social connections modify this association in older Japanese adults. Data were collected by a cross-sectional survey of 15,302 community-dwelling adults aged ≥ 65 in Osaka, Japan, 2022. Frailty was measured using the validated Kihon Checklist, with a score of ≥ 8 classified as frailty. A balanced meal was defined as a combination of “staple food, main dishes, and vegetables”, in line with Japan’s health promotion policies. Participants without at least one such meal per day were classified as having an “unbalanced diet.” Social connections included social participation, social contact, and social support. Social participation was defined as participation in any of the organizations or groups. Social contact was defined as regular contact with family or friends. Social support was the presence of a supportive social network. Sex-stratified adjusted logistic models were employed to examine the associations between an unbalanced diet and frailty. We further tested interactions between an unbalanced diet and each social connection variable on both multiplicative and additive scales. The overall prevalence of frailty was 23.1%. Men have a higher proportion of unbalanced diet (29.6%) than women (15.1%). We found an unbalanced diet was associated with frailty in men (OR 1.70, 95% CI 1.38–2.11) and women (OR 1.77, 95% CI 1.38–2.26). In men, significant multiplicative and negative additive interactions were observed between an unbalanced diet and social participation, social contact, and social support (all p < 0.05). No significant interactions were found in women. We identified significant associations between an unbalanced diet and frailty in older Japanese adults. This association varied by social connections status specifically in men. Nutrition-related efforts for frailty may need to consider social context in older men. However, our study was limited by its cross-sectional design.