Sedentary time and the risk of metabolic syndrome: A systematic review and dose-response meta-analysis

The dose-response association between sedentary time and the risk of metabolic syndrome is unclear, which indicates an important knowledge gap in public health. The objective of this study was to determine the categorical and continuous dose-response associations between sedentary time and the risk of metabolic syndrome. A systematic literature search of English articles published in PubMed, CINHAL, Embase, and Web of Science Core Collection prior to June 2022 was conducted. All cohort and cross-sectional studies that examined the association between sedentary time and the risk of metabolic syndrome were considered, and duplicate and non-related studies were excluded. Data extraction using a standardized chart and quality assessment using two appraisal tools were also performed. Two independent reviewers were involved in these processes. In categorical meta-analyses, the pooled effect sizes for metabolic syndrome associated with different categories of sedentary time were calculated by comparing the highest and intermediate with the lowest categories. In continuous meta-analyses, the linear and nonlinear dose-response associations were estimated using generalized least squares and restricted cubic spline models, respectively. Data were collected and analyzed from March to June 2022. Four prospective cohort studies and 22 cross-sectional studies with 105,239 participants and 16,185 MetS cases were included in this study. In categorical analyses, both intermediate (median duration: 4.11 h/day; pooled OR: 1.17, 95% CI: 1.08-1.26, P < 0.001) and high levels (median duration: 7.26 h/day; pooled OR: 1.71, 95% CI: 1.43-2.04, P < 0.001) of total sedentary time were significantly associated with an increased risk of metabolic syndrome. Similarly, a significant association between screen time and the risk of metabolic syndrome was also found in intermediate (median duration: 2.22 h/day; pooled OR: 1.20, 95% CI: 1.10-1.32, P < 0.001) and high levels (median duration: 3.40 h/day; pooled OR: 1.63, 95% CI: 1.44-1.86, P < 0.001) of exposure. Of note, these associations were significantly stronger in women. Different patterns of the behavior-disease association were not observed in children, adolescents, and adults. The findings of continuous meta-analyses could not provide solid evidence for the linearity and nonlinearity of the behavior-disease association. This study demonstrated that long-time sedentary behavior was associated with a higher risk of MetS independent of physical activity and the patterns of association varied by gender instead of age. These findings have implications for future guideline recommendations on physical activity, sedentary behavior, and prevention of metabolic syndrome.