Diurnal timing and volume of physical activity in relation to metabolic syndrome in US adults: a population-based cohort study.

Objective: To examine the independent and joint associations between physical activity (PA) timing and volume patterns in relation to metabolic syndrome (MetS).

Methods: Data from the NHANES 2011-2014 cycles, involving 5065 participants, were used. PA was measured using triaxial accelerometers. PA timing patterns were determined using the K-means clustering algorithm, and PA volumes were categorized based on tertiles (low, moderate, and high). Logistic regression models were used to assess the associations between PA patterns and MetS and its components. We also used restricted cubic spline curves to fit the PA to the MetS and its component non-linear associations.

Results: Three distinct PA timing patterns were identified using K-means clustering (morning, midday-afternoon, and late afternoon-evening). Independent analyses indicated that engaging in PA during the morning or midday-afternoon PA was with lower odds of MetS compared to late afternoon-evening. The adjusted odds ratios (95% confidence intervals) were 0.79 (0.63-0.99) and 0.78 (0.62-0.98), respectively. In joint analyses, compared with the late afternoon-evening/low PA pattern, the morning and midday-afternoon PA timing patterns were associated with lower odds of MetS when combined with moderate or high PA volume. In contrast, the late afternoon-evening PA pattern was significantly associated with lower odds of MetS only at high PA volumes. Additionally, a nonlinear association with MetS was identified in the morning PA pattern, whereas dose-dependent associations with MetS were observed in the midday-afternoon and late afternoon-evening PA patterns.

Conclusions: Our study shows that morning and midday-afternoon PA patterns are associated with lower odds of MetS compared to late afternoon-evening PA. Higher total PA volume is also linked with lower odds of MetS. Conversely, prolonged PA during the late evening or nighttime is associated with higher odds of poorer metabolic outcomes.