Background: Aspirin has been found to prevent angiotensin II-induced hypertension and to induce nitric oxide (NO) release from vascular endothelium. Low-dose aspirin has also been shown to reduce blood pressure (BP) when administered at bedtime, as opposed to upon awakening, in untreated hypertensive patients and high-risk pregnant women. Accordingly, we investigated the effects on ambulatory BP of aspirin administered at different times of the day in prehypertension.
Methods: We studied 244 subjects with prehypertension, 43.0 +/- 13.0 years of age, randomly divided in three groups: nonpharmacological hygienic-dietary recommendations; the same recommendations and aspirin (100 mg/day) on awakening; or the same recommendations and aspirin at bedtime. BP was measured for 48 consecutive hours before and after 3 months of intervention.
Results: Ambulatory BP was unchanged in subjects randomized to either nonpharmacological intervention or aspirin on awakening. A significant ambulatory BP reduction was, however, observed in the subjects who received aspirin at bedtime (decrease of 6/3 mm Hg in the 24-h mean of systolic (SBP)/diastolic BP (DBP), respectively; P < 0.001), without changes in heart rate (HR) from baseline. BP was homogeneously controlled along the 24 h after bedtime aspirin administration (6/4 mm Hg reduction in activity mean of SBP/DBP; 6/3 mm Hg reduction in sleep-time mean, respectively).
Conclusions: This prospective trial documents a significant effect on BP of low dose aspirin only when ingested at bedtime by prehypertensive subjects. The timed administration of low-dose aspirin could thus provide a valuable and cost-effective approach for BP control in subjects at elevated risk of developing hypertension.
Trial registration: ClinicalTrials.gov NCT00295542.