Nathan T. Adams1, Jillian Poles1, Craig Paterson2, Lee Stoner, FACSM1. 1University of North Carolina at Chapel Hill, Chapel Hill, NC. 2University of Gloucestershire, Gloucester.

BACKGROUND: Acute bouts of prolonged sitting have been found to detrimentally impact the cardiovascular system, including acute increases in blood pressure (BP). Repeated increases in BP can damage the heart and blood vessels. While the responses to prolonged sitting have been reported independently in many studies, a multi-level meta-analysis that can consider non-independence of measurements and effect sizes of blood pressure change during prolonged sitting has not been explored. Therefore, we conducted a meta-analysis to track BP change during uninterrupted prolonged sitting. METHODS: Four databases were searched through September 2021. Inclusion criteria were sitting trials > 1 hour, adults (18+ years old), and brachial measurements of either mean arterial pressure (MAP), systolic BP (SBP), diastolic BP (DBP) obtained at a minimum of three time points in the seated posture. Trials with interruption strategies were eligible if they included an uninterrupted prolonged sitting control condition. A random-effects 3-level meta-analysis was conducted to account for the potential interdependence of multiple data points from the same participants and the same trials. RESULTS: Twenty-four articles (28 trials, n = 465) met inclusion criteria. Prolonged uninterrupted sitting resulted in significant increases of all BP indices; MAP (ꞵ = 0.60 mmHg/hr, 95% CI: 0.18, 1.02, p = 0.004), SBP (ꞵ = 0.60 mmHg/hr, 95% CI: 0.30, 0.90, p < 0.001), and DBP (ꞵ = 0.48 mmHg/hr, 95% CI: 0.18, 0.72, p < 0.001). In trials where sitting was interrupted with either standing, aerobic-, or simple resistance exercise, there were non-significant effects of time on MAP (ꞵ = 0.06 mmHg/hour, 95% CI: -0.24, 0.36, p = 0.750), and small significant decreases in SBP (ꞵ = -0.24 mmHg/hr, 95% CI: -0.42, -0.06, p = 0.018) and DBP (ꞵ = -0.24 mmHg/hr, 95% CI: -0.42, 0.06, p = 0.004). Significant heterogeneity between studies was observed for all outcomes (MAP, SBP, DBP: I2 > 85%, p < 0.001). CONCLUSIONS: All BP indices increased progressively with uninterrupted sitting. Over time, prolonged-sitting-induced increases in BP could lead to decreased elasticity in arteries, left-ventricular hypertrophy, or other cardiovascular diseases and symptoms. While considerable heterogeneity was observed (potentially due to variability in age and baseline BP status), results suggest that detrimental increases in BP can be avoided by regularly interrupting sitting.

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