In lower-income countries, association of prolonged sitting with mortality is more pronounced
Association of Sitting Time With Mortality and Cardiovascular Events in High-Income, Middle-Income, and Low-Income Countries
Introduction and methods
Prolonged sitting has become commonplace in modern society, owing to the popularization of electronic products, an increase in sedentary occupations, and changing patterns of transportation. Over the past decade, the total sitting time among American adults has increased by nearly 1 hour per day [1,2]. Research from high-income countries and China shows that prolonged sitting is associated with mortality and CVD [3-7]. However, sedentary behavior can vary substantially by socioeconomic status and social class [8,9].
Aim of the study
The aim of this study was to study the association of sitting time with mortality and major CVD in low-, middle- and high-income countries.
The researchers used data from 105,677 35-70-year-olds who participated in the Prospective Urban Rural Epidemiology (PURE) study, a large-scale, prospective cohort study based on the general population in Africa, Europe, the Middle East and North and South America. Participants were recruited from January 1, 2003 and followed up until August 31, 2021. Median follow-up was 11.1 years (IQR: 8.6-12.2). They came from 21 countries, classified according to the 2006 World Bank classification into high-income countries (n = 4), upper-middle-income countries (n = 7), lower-middle-income countries (n = 5) and low-income countries (n = 5). Information on sitting time and physical activity was collected using a validated questionnaire, the Physical Activity Questionnaire (IPAQ).
The primary outcome was the composite of all-cause mortality and major CV events, defined as cardiovascular mortality, nonfatal myocardial infarction, stroke, or heart failure. The secondary outcomes included the individual components of the primary outcome.
- Compared with the reference group (<4 h/day sitting), prolonged sitting (≥8 h/day) was associated with an increased risk of the composite outcome (HR: 1.19; 95%CI: 1.11-1.28; P for trend <0.001), total mortality (HR: 1.20; 95%CI: 1.10-1.31; P for trend <0.001) and major CV events (HR: 1.21; 95%CI: 1.10-1.34; P for trend <0.001).
- Stratified by country income level and compared with the reference group (<4 hours/day sitting), the risk of prolonged sitting (≥8 hours/day) on the composite outcome was higher in low- and lower-middle-income countries (HR: 1.29; 95%CI: 1.16-1.44) than in upper-middle and high-income countries (HR: 1.08; 95%CI: 0.98-1.19; P for interaction = 0.02).
- Stratified by geographic region and compared with the reference group (<4 hours/day sitting), prolonged sitting (≥8 hours/day) was associated with an increased risk of the composite outcome in all regions except North America and Europe (HR: 1.06; 95%BI: 0.89-1.26; P for interaction = 0.004); the risk was highest in South Asia (HR: 1.82; 95%BI: 1.41-2.34).
- Compared with the reference group (<4 h/day sitting and high physical activity level), participants who sat for 8 or more hours per day had a 17-50% higher risk of the composite outcome across physical activity levels; the risk attenuated along with increased physical activity levels.
Prolonged sitting is associated with an increased risk of mortality and major CV events, especially in low-income and lower-middle-income countries. Reduction of sitting time combined with increased physical activity could be an important strategy to prevent premature death and CVD.