Key result
Sleep restriction with circadian misalignment significantly increased 24-hour urinary norepinephrine (30 vs 21 μg; P=0.005) and nocturnal heart rate compared to circadian alignment.
Why the study?
Does circadian misalignment combined with sleep restriction impair autonomic function compared to sleep restriction alone in healthy young adults?
Does circadian misalignment combined with sleep restriction impair autonomic function compared to sleep restriction alone in healthy young adults?
Absolute Event Rate: 30% vs 21%
p-value: p=0.005
Circadian misalignment combined with sleep restriction exacerbates autonomic dysfunction compared to sleep restriction alone, providing experimental evidence for a mechanism linking irregular sleep to cardiovascular risk.
Circadian misalignment may impair autonomic function despite equal sleep time; leaves open causal links to hypertension in larger trials.
Insufficient sleep and circadian rhythm disturbances have been each associated with adverse cardiovascular outcomes in epidemiological studies, but experimental evidence for a causal link is scarce. The present study compares the impact of circadian misalignment (CM) to circadian alignment (CA) on human autonomic function using a nonrandomized parallel group design to achieve the same total sleep time in both conditions. After baseline assessments (3 days with 10-hour bedtimes), 26 healthy young adults were assigned to sleep restriction (SR; eight 5-hour bedtimes) with either fixed nocturnal bedtimes (CA; n=13) or bedtimes delayed by 8.5 hours on 4 of the 8 days (CM; n=13). Daytime ambulatory blood pressure and heart rate (HR; CA, n=11; CM, n=10) and 24-hour urinary norepinephrine levels (CA, n=13; CM, n=13) were assessed at baseline and the end of SR. Nocturnal HR and HR variability were analyzed during sleep at baseline and during the fourth and seventh nights of SR (CA, n=8; CM, n=12). SR resulted in a significant increase in daytime HR in both groups, without changes in blood pressure. SR increased 24-hour urinary norepinephrine in the CM group (30±4 versus 21±2 μg), but not in the circadian alignment group (group×condition, P=0.005). In contrast to the lack of detectable impact of CM on daytime autonomic function, SR with CM elicited greater increases in nocturnal HR, as well as greater reductions in vagal indices of HR variability, than SR without CM (group×condition, P<0.05). In conclusion, SR and CM both result in impaired autonomic function that could lead, under chronic conditions, to enhanced cardiovascular risk.
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Grimaldi et al. (2016) studied Healthy (n=26). Sleep restriction with circadian misalignment vs. Sleep restriction with circadian alignment (fixed 5-hour bedtimes) was evaluated on 24-hour urinary norepinephrine levels (p=0.005). Sleep restriction with circadian misalignment significantly increased 24-hour urinary norepinephrine (30 vs 21 μg; P=0.005) and nocturnal heart rate compared to circadian alignment.
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