Using data from the CLHLS, we examined the relationship between physical activity and all-cause mortality among Chinese older adults. Our findings indicate that maintaining exercise habits and transitioning from inactivity to an active lifestyle are associated with longer survival, regardless of covariate consideration.In exploring the nexus between physical activity and all-cause mortality, particularly in the elderly, many studies have provided consistent insights as presented in this article. For example, a longitudinal study of 85,545 elderly Australians found that a high-quality diet combined with high levels of moderate-to-vigorous physical activity (MVPA) significantly reduced risks of cardiovascular disease (CVD) and all-cause mortality [23]. The National Health and Nutrition Examination Survey (NHANES) 2011–2014 data emphasized that objective measures of physical activity, above age, are the strongest predictors of all-cause mortality [24].A retrospective cohort study utilizing Korean National Health and Nutrition Examination Survey (KNHANES)-mortality linked data underscored the joint influence of physical activity and socioeconomic status (SES) on mortality, revealing a notable decrease in mortality risk among older adults with low SES who engage in regular physical activity [25]. Similarly, among low-income older Americans, a cohort study showed that high sitting time is an independent risk factor for all-cause and CVD mortality, while leisure-time physical activity (LTPA) mitigated this risk [26].In the Indian context, the Longitudinal Aging Study evidence suggests that adequate physical activity significantly lowers the risk of CVD among the elderly, emphasizing the importance of regular exercise in reducing CVD burden [27].Collectively, these findings highlight the pivotal role of physical activity in promoting longevity and reducing all-cause mortality in the elderly, transcending geographical and socioeconomic barriers. The shift from a sedentary to an active lifestyle is associated with longer survival, a benefit consistent across varying covariates. This underscores the need for public health interventions that encourage and facilitate active lifestyles among the elderly, thereby enhancing their health and well-being.
WWI has garnered attention as an emerging indicator for assessing obesity. Experimental findings indicate that a reduction in WWI significantly decreases the risk of multimorbidity in older adults [28] and is positively associated with all-cause mortality in this population [13].All these results strongly support the premise of this paper that higher WWI values are associated with an increased risk of death. Furthermore, we identified that a WWI threshold of ≥ 11.38 cm/√kg may indicate an elevated risk of death among Chinese older adults, as demonstrated by the RCS curve. This finding slightly differs from those of other studies.For example, according to the NHANES database, a study of a non-Asian population aged 18 to 80 years found that when WWI exceeded 10.46 cm/√kg, all-cause mortality increased by 20% for each unit increase in WWI [HR = 1.20, 95% CI: (1.08, 1.33)] [29]. Additionally, a cohort study conducted in rural China recruited 10,338 non-hypertensive participants aged 18 years and older in Henan Province. This study found a positive association between WWI and the prevalence of hypertension over a subsequent six-year follow-up, revealing a significantly higher odds ratio (OR) for developing hypertension, particularly when WWI was ≥ 10.91 cm/√kg [OR = 1.50, 95% CI: 1.24–1.82] [29]. The subtle differences in WWI thresholds may be attributed to the fact that the study population in this paper comprised individuals aged 60 years and older.
Given that both physical activity as well as WWI have been shown to be strongly associated with all-cause mortality, a thought-provoking question is: Is there some potential correlation between the two? In order to explore this topic, subgroup analyses and interaction analyses were carefully designed with the aim of revealing possible subtle links between them.The results of the study showed significant interaction effects between physical activity and a range of socio-demographic factors and lifestyle habits, including gender, marital status, alcohol consumption, and health insurance status, when all-cause mortality was taken into account. These findings not only enrich our knowledge of health risk factors, but also highlight the importance of individual differences in influencing health outcomes.However, it is worth noting that when exploring whether there was an interaction between physical activity and WWI, our analyses did not find a statistically significant association between the two (P for interacton = 0.462).It is important to note that the assessment of physical activity in our study was based on self-reported data, which could introduce potential bias [30].
Further, we analysed in depth the mediating effect of WWI between physical activity level and survival status. By constructing a mediating effect model, we found that WWI partially mediated this relationship. Although the proportion of the mediating effect was relatively low, at 3.06%, this finding is still clinically significant. Physical activity may have an indirect positive impact on all-cause mortality by reducing WWI values, which in turn may contribute to lowering all-cause mortality.Furthermore, despite the low proportion of the mediating effect, it serves as a reminder that other potential mediating variables or pathways should not be overlooked when exploring the relationship between physical activity and health outcomes. Future research could further explore how physical activity affects all-cause mortality through other mechanisms, such as improving cardiovascular health[31], reducing the inflammatory response[32], strengthening the immune system[33], promoting mental health[34], and improving metabolic function[35], and how these mechanisms interact with WWI.