Objectively Measured Physical Activity, Sedentary Behavior, and Metabolic Syndrome in Adults: Systematic Review of Observational Evidence.

Objective measurement of physical activity (PA) and sedentary behavior (SB) associated with metabolic syndrome (MetS) has gained more attention among researchers in recent years. Although almost similar trends of results have been reported worldwide, they were not always statistically significant. This systematic review summarizes the evidence of observational studies reporting the associations between objectively measured PA, SB, and MetS in adults. Registration in PROSPERO was made (CRD42017078929). Literature search was conducted in the PubMed database for observational studies associating objectively measured PA and SB with MetS among adults. Secondary manual search was also conducted to find more related studies. A total of 44 studies were included in this systematic review. The quality score of studies obtained using National Institutes of Health Quality Assessment Tool ranged between 4 and 11. For total PA, most studies showed negative association with MetS. Similar association with MetS was reported in most studies assessing moderate-to-vigorous PA (MVPA) (total, bouts, sporadic), vigorous-intensity PA (VPA) (total, bouts), moderate-intensity PA (MPA) (total, bouts), and light-intensity PA (LIPA) bouts. However, more studies assessing LIPA total and LIPA sporadic found no significant association with MetS, with only a few studies reporting negative association. Meanwhile, all studies assessing step counts reported negative association with MetS. In contrast, MetS was positively associated in all studies investigating physical inactivity. MetS was also positively associated in most studies reporting sedentary (SED) time and bouts, while SED breaks showed no significant association with MetS. Further studies are required to ascertain the interaction and independent contribution of objectively measured PA and SB to the overall risk of MetS.