Associations of physical activity, dietary quality, and their changes with all-cause mortality in older Chinese adults: a prospective study

Physical activity (PA) and dietary quality are important modifiable behaviors in later life, but evidence on the association between their changes and all-cause mortality remains limited, particularly among older Chinese adults. We examined the associations of PA, dietary quality, and their joint changes over time with all-cause mortality. This study included 11,528 older adults aged ≥ 65 years from the Chinese Longitudinal Healthy Longevity Survey (2002–2018). Physical activity (PA) was assessed using self-reported activity frequency, and dietary quality was evaluated using the Simplified Healthy Eating Index (SHE) and Dietary Diversity Score (DDS). Separate exposure measures included baseline levels and annualized changes in PA, SHE, and DDS. Joint changes in PA and dietary quality were assessed using 16 prespecified patterns derived from two assessments. In a secondary analysis, group-based multi-trajectory modeling (GBMTM) identified joint trajectories of PA and dietary quality among 6,008 participants with at least three assessments. Multivariable Cox regression models estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality. During 69,288 person-years of follow-up (median follow-up of 6 years), 7,168 participants died. Each 1-point/year increase in ∆PA, ∆SHE, and ∆DDS was associated with lower all-cause mortality risk, with HRs of 0.78 (95% CI: 0.76–0.80), 0.95 (95% CI: 0.92–0.97), and 0.91 (95% CI: 0.88–0.95), respectively. Among the joint change patterns, improvement in either behavior was generally associated with a lower mortality hazard than persistently low levels of both. Persistently high PA and dietary quality were associated with the lowest hazards in the PA-SHE and PA-DDS analyses (HRs, 0.55–0.57; both P < 0.01). GBMTM showed directionally consistent associations. No significant multiplicative or additive interaction between PA and diet quality was observed. These findings suggested that sustained high PA and diet quality in were associated with reduced all-cause mortality risk among Chinese adults aged 65 years and older, highlighting the importance of maintaining regular PA and healthy dietary habits for extending lifespan.