Low muscle function and obesity defined by handgrip strength or sit-to-stand performance in relation to depressive symptoms and cognitive impairment in Korean older adults.

Abstract

Background Low muscle function and obesity often coexist in later life, but this combined phenotype is usually defined by handgrip strength (HGS) alone. Whether an upper-extremity strength test and a lower-extremity performance test show comparable associations with depressive symptoms and cognitive impairment is unclear. Methods This exploratory cross-sectional study included 938 community-dwelling Korean older adults aged 65 years or older. Low HGS followed the 2019 Asian Working Group for Sarcopenia criteria, low 30-second sit-to-stand (30-s STS) performance was the sex-specific lowest quartile, and obesity was a body mass index ≥ 25 kg/m². Participants were cross-classified into normal, low-muscle-function-only, obesity-only, and combined groups. Logistic regression was adjusted for age, sex, education, living alone, physical activity, and medications, and interaction was tested on multiplicative and additive scales. Results Relative to the normal group, the combined HGS-based group was associated with depressive symptoms (odds ratio 4.18, 95% confidence interval 2.29-7.62) and cognitive impairment (2.58, 1.53-4.37); 30-s STS-based estimates were 2.99 and 1.89. The combined groups did not differ from the low-muscle-function-only groups (all p > 0.5), and no interaction was significant. Discriminative ability was similar for the two tests. Conclusion Low muscle function rather than its combination with obesity was the dominant correlate of depressive symptoms and cognitive impairment. These exploratory associations require longitudinal confirmation.