Association of Sitting Time With Mortality and Cardiovascular Events in High-Income, Middle-Income, and Low-Income Countries based on the PURE study

Increased sitting time has become common in modern society owing to the popularization of electronic products, an increase in sedentary occupations, and changing patterns of transportation. Serial analyses reported total sitting time has substantially increased by nearly 1 hour per day among adults over the past decade in the US. The recent World Health Organization (WHO) 2020 global physical activity guideline now recommends limiting sedentary time and engaging in high levels of physical activity to reduce the detrimental effects of sitting time. Thus far, current evidence has been almost exclusively in high-income countries and China. Previous studies suggested that the contextual patterns in which sedentary behavior occurs might vary substantially by socioeconomic status and social class. On June 15, 2022, JAMA Cardiology published a new analysis aiming to determine the associations of self-reported sitting time with all-cause mortality and major cardiovascular diseases (CVD) in countries at varying income levels using data from the Prospective Urban Rural Epidemiology (PURE) study.

This population-based cohort study included participants aged 35 to 70 years recruited from January 1, 2003, and followed up until August 31, 2021, in 21 high-income, middle-income, and low-income countries with a median follow-up of 11.1 years. Daily sitting time measured using the International Physical Activity Questionnaire (IPAQ). The primary outcome was the composite of all-cause mortality and major CVD (defined as cardiovascular death, myocardial infarction, stroke, or heart failure).

Of 105 677 participants, 61 925 (58.6%) were women, and the mean (SD) age was 50.4 (9.6) years. During follow-up, 6233 deaths and 5696 major cardiovascular events (2349 myocardial infarctions, 2966 strokes, 671 heart failure, and 1792 cardiovascular deaths) were documented. Compared with the reference group (<4 hours per day of sitting), higher sitting time (≥8 hours per day) was associated with an increased risk of the composite outcome (hazard ratio [HR], 1.19; 95% CI, 1.11-1.28; P for trend < .001), all-cause mortality (HR, 1.20; 95% CI, 1.10-1.31; P for trend < .001), and major CVD (HR, 1.21; 95% CI, 1.10-1.34; P for trend < .001). When stratified by country income levels, the association of sitting time with the composite outcome was stronger in low-income and lower-middle–income countries (≥8 hours per day: HR, 1.29; 95% CI, 1.16-1.44) compared with high-income and upper-middle–income countries (HR, 1.08; 95% CI, 0.98-1.19; P for interaction = .02). Compared with those who reported sitting time less than 4 hours per day and high physical activity level, participants who sat for 8 or more hours per day experienced a 17% to 50% higher associated risk of the composite outcome across physical activity levels; and the risk was attenuated along with increased physical activity levels.

That is, reducing sedentary time along with increasing physical activity may be an important strategy for easing the burden of premature deaths and CVD in economically diverse settings, especially in low-income and lower-middle–income countries.


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