Can grip strength capture what chair standing does? methodological considerations on functional measures and successful aging in three international cohorts

Population aging has accelerated globally, making successful aging a key public health priority. Zhuang and Gao address the prospective association between cumulative average grip strength and successful aging using three international cohorts. While their multi-cohort design offers valuable cross-population insights, several methodological choices warrant consideration. Grip strength may not fully capture functional determinants of successful aging. Self-reported chronic disease introduces misclassification bias varying across socioeconomic groups. The two-stage temporal design does not fully address selection bias and cross-cohort comparability from heterogeneous exposure windows. Additionally, the cohort-relative cognitive threshold undermines cross-population comparability. These considerations highlight the need for methodological reflection and suggest directions for strengthening future multi-cohort studies.