Smart wearable device ownership and depressive symptoms among older adults in China: a longitudinal fixed-effects analysis

Background Smart wearable devices are increasingly incorporated into later-life health management, but longitudinal evidence concerning device ownership and depressive symptoms remains limited. Objective This study examined the within-person association between smart wearable device ownership and depressive symptoms among older adults in China, alongside concurrent psychosocial and behavioral characteristics and variation across digital and sociodemographic contexts. Methods Data were drawn from the 2018, 2020, and 2023 waves of the China Longitudinal Aging Social Survey. The baseline analytical sample comprised 30,255 person-year observations from 16,752 respondents. Two-way fixed-effects models were estimated using 22,536 observations from 9,033 repeatedly observed respondents, including 902 ownership switchers. Depressive symptoms were measured using a reverse-coded nine-item CES-D score. Additional analyses examined health perception, social adaptation, leisure participation, mobile phone proficiency, sociodemographic heterogeneity, sample selection, and attrition. Results Smart wristband or smartwatch ownership was positively associated with the reverse-coded CES-D score within individuals ( β = 0.719, 95% CI [0.414, 1.024]), indicating fewer depressive symptoms during waves in which ownership was reported. The association remained positive across multiple sensitivity analyses. Ownership also covaried positively with health perception, social adaptation, and leisure participation, although their contemporaneous measurement precluded causal mediation claims. Contemporaneous analyses showed a more favorable ownership association at higher levels of self-rated mobile phone proficiency (linear interaction β = 1.890, p < .001), whereas prior-proficiency analyses produced weaker evidence. Heterogeneity was statistically supported for hukou origin, but not for gender, age, or education after multiplicity adjustment. Conclusions Smart wearable device ownership was positively associated with fewer depressive symptoms within individuals, but the findings do not establish a causal effect. Digital capabilities and institutional context appear important for understanding heterogeneity in the ownership–depressive-symptom association. Clinical trial number Not applicable.