Blunted heart rate recovery to spontaneous nocturnal arousals in short-sleeping adults.

Chronic insufficient sleep is a common occurrence around the world and results in numerous physiological detriments and consequences, including cardiovascular complications. The purpose of the present study was to assess the relationship between habitual total sleep time (TST) measured objectively via at-home actigraphy and heart rate (HR) reactivity to nocturnal cortical arousals. We hypothesized that short habitual TST would be associated with exaggerated cardiac reactivity to nocturnal cortical arousals. Participants included 35 healthy individuals [20 men, 15 women, age: 24 ± 1 yr, body mass index (BMI): 27 ± 1 kg/m2], and were split using a median analysis into short-sleeping (SS; n = 17) and normal-sleeping (NS; n = 18) adults based on a minimum of 7 days of at-home actigraphy testing. All participants underwent a full overnight laboratory polysomnography (PSG) testing session, including continuous HR (electrocardiogram, ECG) sampling. HR reactivities to all spontaneous cortical arousals were assessed for 30 cardiac cycles following the onset of the arousal in all participants. Baseline HR was not significantly different between groups (P > 0.05). Spontaneous nocturnal arousal elicited an augmented HR response in the SS group, specifically during the recovery period [F(5.261,163.08) = 3.058, P = 0.01, ηp2 = 0.09]. There were no significant differences in HR reactivity between sexes [F(3.818,118.368) = 1.191, P = 0.318]. These findings offer evidence of nocturnal cardiovascular dysregulation in habitual short sleepers, independent from any diagnosed sleep disorders.NEW & NOTEWORTHY Short habitual sleep is associated with poor cardiovascular outcomes, but mechanisms remain equivocal. The present study used objectively measured habitual sleep via wrist actigraphy, and reports that habitual short sleepers have augmented heart rate recovery responses to spontaneous arousals as determined by gold-standard polysomnography. There were no reported sex differences. The augmented heart rate recovery to spontaneous cortical arousals may be an important mechanism contributing to the associations between insufficient sleep and cardiovascular risk.