Joint association of physical function and sleep duration with incident depressive symptoms among middle-aged and older Chinese

TL;DR

This study finds that poor physical function and short sleep duration together increase the risk of developing depressive symptoms in middle-aged and older Chinese adults.

Contribution

The study identifies optimal sleep and physical function combinations to reduce depressive symptoms risk in older Chinese adults.

Findings

Physical dysfunction and short sleep duration independently increase the risk of depressive symptoms.

The combination of physical dysfunction and short sleep duration confers the highest risk for depressive symptoms.

Longer nighttime sleep (≥6 hours) can mitigate depressive symptoms risk in individuals with physical dysfunction.

Abstract

To explore the independent, joint, interactive, and mediating effects of physical function (PF) and sleep duration (SD) on incident depressive symptoms (IDS) among Chinese adults aged ≥ 45 years, and to recommend appropriate PF-SD combination strategy to lower IDS risk.

Data were obtained from the China Health and Retirement Longitudinal Study (CHARLS), with a nine-year follow-up from 2011 to 2020. Physical function was assessed with a 9-item questionnaire, SD was self-reported, and IDS was defined by the Center for Epidemiological Studies Depression Scale ( CES-D). Cox regression, restricted cubic spline (RCS) model, Subgroup and sensitivity analysis, interaction, and mediation analyses were applied.

Among 6,189 community-dwelling adults (mean age 56.6 ± 7.9 years; 52.4% male), 1,815 incident IDS events (29.3%) were documented over 9 years of follow-up. Both physical dysfunction (PD) and short sleep duration (SSD) were independently associated with IDS (PD: HR = 1.37; SSD: HR = 1.15–1.34; all P < 0.05). The SSD–IDS association remained robust across PD and non-physical dysfunction (NPD) subgroups (HR = 1.13–1.38; all P < 0.05 except for midday nap duration [MND] < 30 min in NPD). Relative to the PD + SSD referent, all other combinations exhibited significantly lower hazard ratios (HR = 0.53–0.85; all P < 0.05). Restricted cubic spline analyses revealed non-linear relationships of total sleep duration (TSD) and nighttime sleep duration (NSD) with IDS (P for non-linearity = 0.002), with no further risk reduction beyond TSD > 8 h or NSD > 7.5 h (both P > 0.05). Mediation analysis indicated that TSD and NSD accounted for 3.55% and 4.0%, respectively, of the PD–IDS effect.

PD and SSD are independent risk factors for IDS among middle-aged and older Chinese, with PD + SSD combination conferring the highest risk. Recommended risk-mitigation strategies are: for NPD individuals, NSD ≥ 6 h; for PD individuals, NSD ≥ 6 h or MND ≥ 30 min. TSD and NSD partially mediate the PD-IDS relationship. Long sleep duration did not increase the risk of IDS.

The online version contains supplementary material available at 10.1186/s12889-026-26677-x.

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