Background Questions remain about the effect on mortality of physical activity and sedentary behaviour over time. We summarized the evidence from studies that assessed exposure from multiple time points and critiqued the analytic approaches used. Methods A search was performed on MEDLINE, Embase, Emcare, Scopus and Web of Science up to January 2021 for studies of repeatedly assessed physical activity or sedentary behaviour in relation to all-cause or cause-specific mortality. Relative risks from individual studies were extracted. Each study was assessed for risk of bias from multiple domains. Results We identified 64 eligible studies (57 on physical activity, 6 on sedentary behaviour, 1 on both). Cox regression with a time-fixed exposure history (n = 45) or time-varying covariates (n = 13) were the most frequently used methods. Only four studies used g-methods, which are designed to adjust for time-varying confounding. Risk of bias arose primarily from inadequate adjustment for time-varying confounders, participant selection, exposure classification and changes from measured exposure. Despite heterogeneity in methods, most studies found that being consistently or increasingly active over adulthood was associated with lower all-cause and cardiovascular-disease mortality compared with being always inactive. Few studies examined physical-activity changes and cancer mortality or effects of sedentary-behaviour changes on mortality outcomes. Conclusions Accumulating more evidence using longitudinal data while addressing the methodological challenges would provide greater insight into the health effects of initiating or maintaining a more active and less sedentary lifestyle.

中文翻译：

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成年期身体活动和久坐行为与全因和特定原因死亡率的关系：对分析策略和研究结果的系统评价

背景问题仍然存在于身体活动和久坐行为对死亡率的影响。我们总结了从多个时间点评估暴露的研究的证据，并批评了所使用的分析方法。方法截至 2021 年 1 月，在 MEDLINE、Embase、Emcare、Scopus 和 Web of Science 上进行搜索，以寻找与全因或特定原因死亡率相关的反复评估的身体活动或久坐行为的研究。提取了个别研究的相对风险。每项研究都评估了来自多个领域的偏倚风险。结果 我们确定了 64 项符合条件的研究（57 项关于身体活动，6 项关于久坐行为，1 项关于两者）。具有时间固定暴露史 (n = 45) 或时变协变量 (n = 13) 的 Cox 回归是最常用的方法。只有四项研究使用了 g 方法，这些方法旨在调整随时间变化的混杂因素。偏倚风险主要源于对时变混杂因素、参与者选择、暴露分类和测量暴露变化的调整不足。尽管方法存在异质性，但大多数研究发现，与始终不运动相比，在成年期持续或越来越多地运动与较低的全因和心血管疾病死亡率相关。很少有研究检查身体活动变化和癌症死亡率或久坐行为变化对死亡率结果的影响。结论 在解决方法学挑战的同时，使用纵向数据积累更多证据，可以更深入地了解开始或保持更积极和更少久坐的生活方式对健康的影响。