Taking anti-hypertensives at bedtime improves blood pressure control and significantly lowers cardiovascular risk, according to a large new study.

The researchers followed 19,000 patients who took their pills upon waking or at bedtime. The bedtime cohort had nearly half the risk (45% reduction) of dying from or suffering heart attacks, stroke or heart failure compared to their morning medication peers.

The analysis was adjusted to account for factors such as age, sex, type 2 diabetes, kidney disease, smoking and cholesterol levels.

Hypertension treatment guidelines do not specify preferred medication timing. But the common clinician prescription – to take them early to lower morning blood pressure – is “misleading,” claims Ramón C. Hermida, Ph.D. He and his colleagues determined that the average systolic blood pressure during sleep is the most significant and independent indication of cardiovascular disease risk. Furthermore, no studies show that morning hypertension treatment lowers the risk of cardiovascular disease, said Hermida, of the University of Vigo, Spain.

“[D]ecreasing the average systolic blood pressure while asleep and increasing the sleep-time relative decline in blood pressure towards more normal dipper blood pressure patterns are both significantly protective, thus constituting a joint novel therapeutic target for reducing cardiovascular risk,” Hermina concluded.

The research is part of the Hygia Project, composed of 40 primary care centers in northern Spain. A total of 292 doctors are involved in the project and have been trained in ambulatory blood pressure monitoring.