Bidirectional reallocations of sitting time, physical activity, and sleep in relation to risk of all-cause mortality and cardiovascular disease: An analysis of the Prospective Urban Rural Epidemiology (PURE)-China cohort study
Year: 2026
Type: article
Abstract: • A J-shaped association between daily sitting time and risks of all-cause mortality and cardiovascular disease was found in the PURE-China cohort, with increased risks at both low and high sitting levels. • Reallocating 30 min of sitting to physical activity in individuals sitting ≥4 h/day linked to 3%–4% lower composite outcome risk and 6%–7% lower all-cause mortality. • A “sitting paradox” was observed in those with low sedentary time (<4 h/day): reallocating 30 min of physical activity or prolonged sleep to sitting was linked to a 4%–6% lower risk of the composite outcome and a 4%–10% lower risk of all-cause mortality. Prolonged sedentary time is associated with adverse outcomes, but evidence in low-exposure ranges remains limited. The health effects of reallocating time between sitting, physical activity, and sleep have not been comprehensively examined. We analyzed 41,733 adults (mean age = 50.6 years) from the Prospective Urban Rural Epidemiology (PURE)-China cohort, recruited between 2005–2009 and followed for a median of 11.9 years. Sitting, physical activity, and sleep were assessed using validated questionnaires. The primary outcome was a composite of all-cause mortality and major cardiovascular events. Cox frailty and isotemporal substitution models were applied. Median sitting time was 3.0 h/day (interquartile range (IQR): 1.7–4.6). Sitting showed a J-shaped association with outcomes, with lowest risk around 4 h/day. Both low (<2 h/day) and high (≥6 h/day) sitting were associated with higher risk. Among participants sitting ≥4 h/day, replacing 30 min of sitting with physical activity was associated with a 3%–4% lower risk of the composite outcome, with stronger associations observed for all-cause mortality (6%–7%). In contrast, among those sitting <4 h/day, reallocating 30 min of physical activity or prolonged sleep to sitting was associated a 4%–6% lower risk of the composite outcome and a 4%–10% lower risk of all-cause mortality. Sitting time demonstrates context-dependent associations with health. The finding that moderate sitting was protective in highly active individuals reflects a potential “sitting paradox”. Our study highlights the bidirectional effects of reallocating sitting, activity, and sleep, underscoring the need for more context-specific guidance.
Institutions: Chinese Academy of Medical Sciences & Peking Union Medical College, Fu Wai Hospital, Nanchang University, First Affiliated Hospital of Jiangxi Medical College, First Affiliated Hospital of Nanchang University, University College London, Chinese University of Hong Kong, Peking Union Medical College Hospital, Capital Medical University, Beijing Anzhen Hospital, Population Health Research Institute, Hamilton Health Sciences, McMaster University, Simon Fraser University
Language: English
Topic: Physical Activity and Health
Subfield: Physiology
Field: Medicine
Domain: Health Sciences
Open Access status: diamond
OpenAlex ID: W7154222468