摘要：Highlights
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Sedentary behavior is associated with higher risks of cancer incidence, cancer mortality and all-cause mortality, as well as earlier onset of cancer and shorter life expectancy, among the Chinese population.
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J-shaped dose–response relationships were observed between daily sedentary time and risks of cancer incidence and mortality, and the lowest risks were seen at 6 h/day.
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Significant adverse effects of sedentary behavior on cancer incidence and mortality are independent of the level of moderate-to-vigorous physical activity.
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The present study indicates that a reduction in sedentary behavior, in addition to an increase in physical activity, is recommended for the prevention of cancer and mortality.<END HIGHLIGHTS>
Background
Inconsistent results have been reported in developed countries for relationships between sedentary behavior and cancer incidence and mortality, and evidence from the Chinese population is scarce. This study aimed to investigate such relationships in large Chinese population-based prospective cohorts and to explore the joint effect and interaction of sedentary behavior and moderate-to-vigorous physical activity (MVPA) on these relationships.
Methods
We included 95,319 Chinese adults without cancer from 3 large cohorts and assessed their sedentary behavior and physical activity with a unified questionnaire. Cancer incidence and mortality were confirmed by interviewing participants or their proxies and checking hospital records and death certificates. Hazard ratios (HRs) and 95% confidence intervals (95%CIs) for cancer and mortality were estimated using Cox proportional hazards regression models.
Results
During 559,002 person-years of follow-up, 2388 cancer events, 1571 cancer deaths, and 4562 all-cause deaths were recorded. Sedentary behavior was associated with increased risk of developing cancer and deaths in a dose–response manner. The multivariable-adjusted HRs (95%CIs) were the following: HR = 1.16, 95%CI: 1.01‒1.33; HR = 1.24, 95%CI: 1.04‒1.48; and HR = 1.15, 95%CI: 1.04‒1.28 for cancer incidence, cancer mortality, and all-cause mortality, respectively, for those having ≥10 h/day of sedentary time compared with those having <6 h/day of sedentary time. Sedentary populations (≥10 h/day) developed cancer or died 4.09 years and 2.79 years earlier, respectively, at the index age of 50 years. Failure to achieve the recommended level of MVPA may further aggravate the adverse associations, with the highest cancer and mortality risks being observed among participants with both ≥10 h/day of sedentary time and <150 min/week of MVPA. Limitations of this study include the fact that physical activity information was obtained via questionnaire instead of objective measurement and that there were insufficient incident cases for the analysis of associations between sedentary behavior and site-specific cancers.
Conclusion
Sedentary behavior was associated with an increased risk of cancer and all-cause mortality among Chinese adults, especially for those with ≥10 h/day of sedentary time. It is necessary to reduce sedentary time, in addition to increasing MVPA levels, for the prevention of cancer and premature death.
Graphical abstract
Image, graphical abstract
