Independent and Joint Association of Physical Activity and Sedentary Behavior on All-Cause Mortality
Introduction The lack of physical activity (PA) and high levels of sedentary behavior (SB) have emerged as significant risk factors for mortality worldwide. Inadequate PA is responsible for over 5 million deaths annually, while prolonged SB is associated with increased risks of chronic diseases and mortality. Despite extensive research in Western populations, there is limited data on the independent and joint associations of PA and SB with all-cause mortality among the Chinese population. This study aimed to prospectively examine these associations in a cohort from southern China.
Background Physical inactivity is a primary risk factor for mortality, contributing significantly to global disease burden. High amounts of SB, such as prolonged sitting, driving, and TV viewing, have been linked to increased risks of chronic diseases and mortality. A meta-analysis involving 54 countries estimated that SB accounts for 3.8% of all-cause mortality. In China, the transformation from a labor-intensive lifestyle to a more sedentary one has raised concerns about the health impacts of reduced PA and increased SB. This study seeks to fill the gap in understanding these associations within the Chinese context.
Methods Study Design and Participants The study included 12,608 participants aged ≥35 years from the China Hypertension Survey, conducted from 2013 to 2014 in Jiangxi Province, southern China. Participants were followed up for an average of 5.4 years. After excluding those with missing data on PA and SB, 11,744 participants were included in the analysis.
Exposure Variables PA and SB were assessed using the International Physical Activity Questionnaire (IPAQ). PA was categorized into low, moderate, and high levels based on metabolic equivalents of task (MET)-minutes per week. SB was defined as any waking behavior with an energy expenditure ≤1.5 METs while sitting or reclining, and participants were categorized based on daily SB duration (<6 h, ≥6 h).
Potential Confounders Baseline demographic characteristics, lifestyle factors, disease history, and body measurement indices were collected and adjusted for in the analysis. These included sex, age, education, residence, employment status, marital status, current smoking, current drinking, sleep duration, history of stroke, myocardial infarction (MI), hypertension, body mass index (BMI), basal metabolism rate (BMR), and visceral fat rate (VAI).
Outcome Ascertainment All-cause deaths were identified through telephone interviews, consultations with local public health doctors, and records from the Jiangxi Province Center for Disease Control and Prevention. Information on death time, location, cause, and diagnostic institution were collected and verified.
Statistical Analysis Data were analyzed using statistical packages R and Empower. Kaplan-Meier curves and Cox proportional hazards models were used to evaluate the associations of PA and SB with all-cause mortality. Additive interactions between PA and SB were assessed using relative excess risk due to interaction (RERI), attributable proportion (AP), and synergy index (S).
Results Participant Characteristics The study included 11,744 participants with an average age of 58.9 years. Mean SB duration was 3.8 hours per day. Participants were categorized into four groups based on PA and SB levels: high PA and SB <6 h, high PA and SB ≥6 h, low to moderate PA and SB <6 h, and low to moderate PA and SB ≥6 h. The group with low to moderate PA and SB ≥6 h had the highest age, VAI, SB duration, systolic and diastolic blood pressure, and the largest proportion of males, current smokers, and individuals with hypertension, stroke, and higher education.
Independent Associations Over the follow-up period, 796 deaths occurred. Participants with high PA had a lower risk of all-cause mortality compared to those with low to moderate PA (5.2% vs. 8.9%; HR: 0.75, 95% CI: 0.61–0.87). Participants with SB ≥6 h had a higher risk of all-cause mortality than those with SB <6 h (7.8% vs. 6.0%; HR: 1.37, 95% CI: 1.17–1.61).
Joint Associations Participants with prolonged SB (≥6 h) and inadequate PA (low to moderate) had the highest risk of all-cause mortality compared to those with SB <6 h and high PA (11.2% vs. 4.9%; HR: 1.67, 95% CI: 1.35–2.06). Even among participants with high PA, prolonged SB (≥6 h) was associated with a higher risk of all-cause mortality compared to SB <6 h (7.0% vs. 4.9%; HR: 1.33, 95% CI: 1.12–1.56).
Discussion The findings of this study highlight the significant independent and joint associations of PA and SB with all-cause mortality among the Chinese population. Adequate PA was associated with a lower risk of mortality, while prolonged SB was linked to a higher risk. The combination of inadequate PA and prolonged SB posed the greatest risk, emphasizing the importance of both increasing PA and reducing SB for mortality prevention.
Mechanisms Several mechanisms may explain these associations. SB has been linked to metabolic risk factors such as elevated fasting glucose, triglycerides, and reduced high-density lipoprotein cholesterol, contributing to increased mortality risk. Additionally, SB can lead to mitochondrial dysfunction, increased inflammation, and cellular senescence. On the other hand, PA promotes favorable changes in glucose tolerance, lipid levels, blood pressure, and BMI, and has direct vascular conditioning effects that reduce health risks.
Strengths and Limitations The study’s strengths include its population-based design, large sample size, and comprehensive adjustment for confounders. However, limitations include the reliance on self-reported PA and SB, potential residual confounding, and the focus on a specific region of China, which may limit generalizability.
Conclusion This study provides robust evidence that both PA and SB are significant modifiable risk factors for all-cause mortality in China. Reducing SB and increasing PA are essential strategies for preventing mortality, particularly in physically inactive or sedentary populations. Public health guidelines should emphasize the importance of minimizing SB alongside promoting PA to improve population health outcomes.
doi.org/10.1097/CM9.0000000000001730
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