Sex Difference in the Association Between Protein Intake and Frailty: Assessed Using the Kihon Checklist Indexes Among Older Adults

Dietary protein intake is inversely associated with physical frailty risk. However, it is unknown whether an association exists between dietary protein intake and comprehensive frailty. To evaluate the association between protein intake and comprehensive frailty in older Japanese adults. This cross-sectional study included 5638 Japanese participants (2707 men and 2931 women) aged ≥65 years from Kameoka City, Kyoto, Japan. Dietary intake was estimated using a validated self-administered food frequency questionnaire. Comprehensive frailty was assessed using a 25-item Kihon Checklist (KCL), which comprised instrumental activities of daily living, mobility disability, malnutrition, oral or eating function, socialization and housebound, cognitive function, and depression domains. A KCL score of 4 to 6 was defined as prefrailty, and ≥7 as frailty. In women, but not in men, protein intake showed a lower prevalence for prefrailty (Q1-Q4, 40.2%, 34.3%, 34.3%, and 36.0%). Higher protein intake was associated with lower prevalence of frailty both in men (32.5%, 28.4%, 28.3%, and 27.3%) and women (35.7%, 31.4%, 27.6%, and 28.2%). Moreover, higher dietary protein intake decreased the odds ratio (OR) for frailty after adjustment for potential confounding factors in both men (OR for highest vs lowest quartile, 0.62; 95% CI, 0.43-0.89; P for trend = 0.016) and women (OR 0.64; 95% CI, 0.45-0.91; P for trend = 0.017). The higher dietary protein intake may be inversely associated with the prevalence of comprehensive frailty in Japanese men and women. Future studies are needed to examine associations of dietary protein intake within KCL domains.