Cardiometabolic Benefit of Replacing Sedentary Time with Light-Intensity Physical Activity: Compositional Data Analysis of the Nijmegen Exercise Study

Purpose The cardiometabolic benefits of replacing sedentary time with light-intensity physical activity (LIPA) are unclear. We studied the associations of hypothetically reallocating sedentary time toward LIPA with changes in cardiometabolic risk factors using thigh-worn accelerometery. We also explored whether reallocation effects differed across subgroups with low, moderate, and high sedentary time and compared proportionally similar reallocations to either LIPA or moderate-to-vigorous physical activity. Methods We assessed physical behaviors across 8 consecutive days using thigh-worn accelerometers among adults from the Nijmegen Exercise Study. Multiple cardiometabolic risk factors were assessed and categorized as 1) anthropometrics, 2) cardiovascular biomarkers, and 3) glucose metabolism. Reallocation effects were estimated for each cardiometabolic risk factor using compositional isotemporal substitution models adjusted for confounders. Analyses were repeated in sedentary time subgroups, that is, <8.5, 8.5-10, and >10 h·d^-1. Results We included 1041 participants (64 (standard deviation 11) yrs; 39.5% female). Reallocating sedentary time toward LIPA was associated with improvements in anthropometrics, some cardiovascular biomarkers, and glucose metabolism; for example, replacing 60 min·d^-1 of sedentary time with LIPA was associated with improvements in body mass index (-0.28 (-0.42 to -0.13) kg·m^-2), estimated glomerular filtration rate (0.68 (0.15 to 1.20) mL·min^-1·1.73m^-2), and glucose (-0.05 (-0.08 to -0.03) mmol·L^-1). Trends suggested that reallocation benefits were strongest in those with >8.5 h·d^-1 of sedentary time. Proportionally similar replacements of sedentary time with either LIPA or moderate-to-vigorous physical activity were associated with similar cardiometabolic benefits. Conclusions Reallocation of sedentary time to LIPA was associated with improvements in cardiometabolic risk factors, predominantly in anthropometrics and glucose metabolism, with greater benefits in the most sedentary individuals. Time reallocation from sedentary time to LIPA may be an effective and arguably feasible strategy to improve population-wide cardiometabolic health.