Heart rate and vascular responses to spontaneous arousals following experimental sleep restriction.

Chronic short sleep duration is associated with cardiovascular disease (CVD) risk, especially in females. The impact of biological sex on hemodynamic reactivity to spontaneous nocturnal arousals following experimental sleep restriction remains largely unknown. We therefore investigated the effect of 9-day 4-h sleep restriction on heart rate (HR) and pulse transit time (PTT) changes following spontaneous arousals in healthy males and females. We hypothesized that HR and PTT reactivity would be augmented following sleep restriction, and these responses would be more robust in females. Nineteen participants (8 females; 23 ± 5 yr) were enrolled into this study, which included two 16-day in-patient studies comprised of sleep restriction (4-h sleep opportunity) and normal sleep (9-h sleep opportunity) study arms. Overnight polysomnography on days 2 (acclimation), 5 (early experimental), 11 (late experimental), and 14 (recovery) of each sleep intervention was used to analyze HR and PTT responses to spontaneous arousals. Sleep restriction did not alter HR or PTT reactivity in males or females during the early experimental phase (day 5; interaction: P > 0.05). The HR response to arousal was altered in a sex-dependent manner following sleep restriction during the late experimental phase (day 11, interaction: P = 0.013). Continued sleep loss resulted in greater PTT reduction following spontaneous arousals in females, but not in males (day 11, interaction: P = 0.007). Sustained sleep curtailment disrupts nocturnal vascular responsiveness to spontaneous arousals, more evident in females than in males. These findings provide mechanistic insight into the sex-specific relationship between shortened sleep duration and CVD risk in females. Clinical Trials Registration: Physiologic Effects of Sleep Restriction, https://clinicaltrials.gov/study/NCT01433315?term=NCT01433315&rank=1, NCT01433315.NEW & NOTEWORTHY Augmented cardiovascular responses to spontaneous nocturnal arousals were previously shown in chronic short-sleeping adults, without known sex differences. Sustained 4-h sleep restriction produced a sex-dependent alteration in heart rate responses to arousals and resulted in a prolonged reduction in postarousal pulse transit time in females only. These findings yield the first sex-specific characterization of nocturnal cardiovascular responses to spontaneous arousals following sleep restriction, and may place females at greater sleep truncation-related cardiovascular disease risk.