OBJECTIVE: Sleep restriction alters daytime cardiac activity, including elevating heart rate (HR) and blood pressure (BP). There is minimal research on the cumulative effects of sleep loss and the response after subsequent recovery sleep on HR and BP. This study examined patterns of HR and BP across baseline, sleep restriction, and recovery conditions using multiple daytime cardiac measurements.
METHODS: Participants (15 healthy men, M = 22.3 years, SD = 2.8) completed an 11-day inpatient protocol with three nights of 10 hours/night baseline sleep opportunity, five sleep restriction nights (5 hours/night sleep opportunity), and two recovery nights (10-hours/night sleep opportunity). Resting HR and BP were measured every two hours during wake. Multilevel models with random effects for individuals examined daytime HR and BP across study conditions and days into the study.
RESULTS: Mean daytime HR was 1.2 ± 0.5 beats/minute lower during sleep restriction compared to baseline, p < 0.001. During recovery, HR was 5.5 ± 1.0 beats/minute higher, p < 0.001, and SBP was 2.9 ± 1.1 mmHg higher, p = 0.009. When accounting for days into the study (irrespective of condition) and measurement timing across the day, HR increased 7.6 beats/minute and SBP increased 3.4 mmHg across the study period, p < 0.001.
CONCLUSIONS: Our findings suggest that daytime HR and SBP increase following successive nights of sleep restriction, even after accounting for measurement time of day. HR and SBP did not recover to baseline levels following two recovery nights of sleep, suggesting longer recovery sleep may be necessary to recover from multiple, consecutive nights of moderate sleep restriction.