Associations Of Actigraphy-assessed Sleep And Nighttime Blood Pressure In Sedentary Office Workers

Blood pressure (BP) follows a diurnal rhythm, with higher values in the daytime and lower values at night. Those whose nocturnal systolic blood pressure (SBP) dips less than 10% of daytime values are at greater risk for adverse cardiovascular outcomes. It remains unclear whether disrupted sleep is associated with nocturnal BP dipping. PURPOSE: To examine the associations between actigraphy-assessed sleep and nocturnal BP dipping in sedentary office workers with elevated BP. METHODS: Data were collected from 172 participants (SBP = 133.8 ± 9.8 mmHg; diastolic BP [DBP] = 81.5 ± 7.1 mmHg; 60.1% female; 83.4% White; age = 44.5 ± 10.8 y; body mass index [BMI] = 31.6 ± 6.6 kg/m2). Sleep was measured using a wrist-worn Actiwatch Spectrum accelerometer concurrently with an Oscar 2 24-hour ambulatory BP monitor on up to 2 occasions per participant. BP was assessed every 30 min during the daytime and 60 min during the nocturnal period (based on participants’ typical bed and wake times). The magnitude of nocturnal dip was calculated as [(daytime SBP - nighttime SBP)/daytime SBP*100]. Linear mixed models were used to examine the associations between sleep and nocturnal SBP dipping, adjusting for age, sex, BMI, race, and daytime SBP. Additional sensitivity analyses accounted for obstructive sleep apnea (OSA) severity in a subsample (n = 115). RESULTS: Across 322 nights of data, participants had a nocturnal SBP = 113.3 ± 11.5 mmHg, dipping 13.7 ± 6.5% lower than daytime SBP. Participants had a mean total sleep time (TST) = 431.1 ± 70.3 min, sleep efficiency (SE) = 90.2 ± 6.2%, wake after sleep onset (WASO) = 40.9 ± 30.4 min, and bedtime = 23.2 ± 1.2 h. For every 1% increase in SE, the magnitude of nocturnal SBP dip increased by 0.27 ± 0.05% (p < 0.001). Each 1-min increase in WASO, the magnitude of nocturnal SBP dip decreased by 0.05 ± 0.01% (p < 0.001). TST, bedtime, sleep midpoint, and sleep onset latency were not statistically significantly associated with the magnitude of nocturnal dipping (each p > 0.3). After accounting for OSA severity, SE and WASO remained significantly associated with the magnitude of nocturnal SBP dip (each p < 0.001). CONCLUSIONS: In sedentary office workers, actigraphy-assessed SE and WASO were associated with nocturnal SBP dipping. Future studies should examine whether improving sleep enhances nighttime BP regulation. Supported by: NIH R01 HL147610, NIH R01 HL134809