Blood pressure medication timing and nocturnal rhythm research

Recent medical research has challenged the long-held theory that taking blood pressure medication at night offers superior cardiovascular protection compared to morning administration. While the 2019 Hygia Chronotherapy Trial suggested a 45% reduction in serious cardiovascular events for nighttime users, subsequent large-scale studies have failed to confirm these results. The TIME study published in The Lancet involving over 21,000 adults in the UK found no significant difference in mortality or hospitalization rates between morning and evening dosing. Similarly, a 2025 Canadian study published in JAMA involving 3,357 patients could not prove that nighttime intake reduces the risk of heart attack, stroke, or heart failure.

Complementary research from the University of Waterloo has investigated why some individuals, known as ‘non-dippers,’ do not experience the natural drop in blood pressure during sleep. Using computational modeling, researchers identified that the synchronization of internal biological clocks is critical. Specifically, even minor shifts in how the kidneys process sodium within a 24-hour cycle can disrupt the body’s ability to lower blood pressure overnight, potentially increasing the risk of kidney disease and cardiovascular events.