Long-term administration of low-dose aspirin has been shown to decrease blood pressure (BP) only when taken at bedtime (before sleep), not daytime. However, the underlying mechanisms are unknown. The objective of the present study was to investigate whether or not sleep plays a role in lowering BP following bedtime administration of low-dose aspirin.
Design and method:
Seven healthy participants completed two in-hospital stays to run through the experimental protocol. Prior to each in-hospital stay, participants took placebo or aspirin (81 mg) at bedtime (within 2 h before sleep) for 2 weeks. During both in-hospital stays, participants were permitted 8 h sleep on the first night (D1), and on the following two nights (D2 and D3) were exposed to interrupted sleep (40 min sleep opportunity and 20 min experimental awakening monitored by staff, repeated between midnight and 6am). Electroencephalogram and ECG were recorded for 24 h on the first night (D1: consolidated sleep) and third night (D3: interrupted sleep).
Slow wave sleep was reduced from D1 to D3 (-11 minutes) in placebo but was slightly increased during the aspirin condition (+2 minutes). There was a significant difference in the delta changes (D1vsD3) between placebo and aspirin stays (p = 0.037). Twenty-four hour heart rate was not different between placebo and aspirin on D1, but heart rate was higher in the placebo than aspirin following interrupted sleep (D3 (p = 0.024)).
The preliminary data suggest that 2 weeks of aspirin at bed-time may preserve slow wave sleep and prevent increase in heart rate when sleep is interrupted. The findings implicate sleep as a mediator of the blood pressure lowering effects of bedtime low-dose aspirin.
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