Relationship Between The 24-Hour Activity Cycle Composition And 24-Hour Blood Pressure

BACKGROUND: Hypertension is a major modifiable risk factor for cardiovascular disease. Ample evidence suggests that the different components comprising the 24-hour activity cycle [24H-ACT; sleep, sedentary behavior (SED), light physical activity (LIPA), moderate to vigorous physical activity (MVPA)] are independently associated with hypertension. However, the relationship between the full 24H-ACT composition and 24-hour mean blood pressure (24H-BP) is not well understood. PURPOSE: Determine the relationship between the composition of the 24H-ACT and 24H-BP in healthy working adults. METHODS: Data for this study come from the Masked Hypertension Study, a multi-site study that examined the prevalence and predictors of masked hypertension. Analysis included 660 participants (59% female, mean [SD] age 45 years [10 years]) were fitted with two different accelerometers worn on their waist and wrist for 24-hours to estimate the 24H-ACT and wore an ambulatory blood pressure monitor to measure 24H-BP with readings taken every 28-30 minutes over a 24-hour period. RESULTS: Over the 24 h day, participants on average spent 28.5% (SD: 4.8%) sleeping, 50.6% (9.7%) being sedentary, 17.5 (7.4%) in LIPA and 3.4% (3.1%) in MVPA. Mean 24 h systolic (SBP)/diastolic (DBP) was 118/73 (10/7) mmHg. After controlling for age, sex, race, ethnicity and site, partial correlations (rp) revealed that sleep was negatively related with 24 h SBP (rp = -0.08, p = 0.04) and DBP (rp = -0.12, p = 0.003). Time spent in SED, LIPA and MVPA were not associated with 24 h SBP (SB: rp = -0.002, LIPA: rp = 0.001, MVPA: rp = -0.01) or DBP (SED: rp = 0.02, LIPA: rp = 0.04, MVPA: rp = 0.03) (all p > 0.25). Substituting 1 hour of sedentary time for sleep was significantly associated with a -0.65 mmHg (95% CI: -1.27 to -0.02) decrease in SBP and -0.67 mmHg (95% CI: -1.14 to -0.20) decrease in DBP. No associations were observed when substituting sedentary time with LIPA [SBP: -0.03 mmHg (95% CI -0.49 to 0.44); DBP: 0.02 mmHg (95% CI: -0.33 to 0.37)] and MVPA [SBP: 0.36 mmHg (95% CI 0.66 to 1.37); DBP: 0.19 mmHg (95% CI: -0.57 to 0.95)]. CONCLUSION: Sleep had a negative relationship with 24H-BP but SED, LIPA, and MVPA did not have a relationship with 24H-BP. These findings suggest greater time spent sleeping is associated with reductions in 24H-BP during a single 24-hour measurement period. P01-HL47540