Effect of five nights of sleep extension on peripheral vascular function: a randomized crossover investigation into long sleep duration

Abstract

Long sleep duration, defined as ≥9 h, is associated with increased cardiovascular mortality. We sought to determine the effect of sleep extension on peripheral vascular health. Twelve middle-aged adults were randomly assigned to spend five nights with 8 h (control) or 10+ hours time in bed (TIB) in a crossover fashion. Sleep was assessed using wrist actigraphy. Peak reactive hyperemia in the forearm was measured using venous-occlusion plethysmography as an index of microvascular vasodilation. Nighttime and morning blood pressure was recorded along with pulse wave velocity (arterial stiffness). Average sleep duration was 7.1 ± 0.3 and 9.3 ± 0.3 h for 8 and 10+ hours TIB (P < 0.001), respectfully. On average, sleep was extended by 127 ± 29 min with nine participants reaching average sleep durations >9 h. Extended sleep did not change nighttime or morning blood pressure, or pulse wave velocity (all P > 0.05). In contrast, peak forearm vascular conductance (FVC, 0.27 ± 0.08 vs. 0.23 ± 0.07 ml/100 ml/min/mmHg, P = 0.02) and total excess blood flow (28 ± 9 vs. 24 ± 11 ml/100 ml, P < 0.01) were increased following sleep extension. The change in FVC and total excess blood flow were inversely correlated with the change in wake after sleep onset and TIB (both r = -0.62, P < 0.05), but not with sleep duration. These results demonstrate that extended time in bed accompanied by long sleep durations does not impair peripheral vascular function, but rather, may increase microvasculature vasodilatory capacity in midlife adults.

Keywords: Arterial stiffness; Blood pressure; Reactive hyperemia; Sleep duration; Sleep extension; Vasodilation.

Fig. 1.

CONSORT diagram showing the flow of participants through each stage of the randomized crossover study.

Fig. 2.

Comparison of brachial and central aortic blood pressure at night (i.e., during sleep) between 8 and 10+ hours time in bed (TIB) protocols. Solid lines represent brachial blood pressure and dashed lines represent central aortic blood pressure. #, significantly different than all other time points (main effect for time, P < 0.05). Values are mean ± SEM.

Fig. 3.

Top panel is a representative figure of the forearm blood flow curve after combining data from all participants. Peak was the highest value measured, which was the first or second measurement for all participants. Total excess blood flow was calculated as the area under the curve above resting blood flow. Lower panel compares total excess blood flow between time in bed (TIB) protocols. Solid individual lines are those that had an average sleep duration >9 hours. Bars are mean ± SEM.

Fig. 4.

Relationship between the change in time in bed with the change in total excess blood flow. Δ, 10+h – 8h TIB is the difference between values measured the night before testing.