The study also shows that participants taking at least one blood pressure pill at bedtime had lower blood pressure while asleep.
Earlier studies have suggested that bedtime dosing of at least one blood pressure medication may help control blood pressure. But the new study is believed to be the first to look at whether the timing makes a difference in terms of heart attacks, strokes, and death.
Ramon C. Hermida, PhD, director of the bioengineering and chronobiology labs at the University of Vigo in Spain, studied 661 people with both high blood pressure and chronic kidney disease.
"Taking blood-pressure-lowering medication at bedtime, compared to [taking] all medication upon awakening, not only improved blood pressure control, but significantly reduced the risk of cardiovascular events," Hermida says in a news release.
The research appears in the Journal of the American Society of Nephrology.
Timing of Blood Pressure Medicines
Hermida's team asked half of the men and women to take all their blood pressure medicine when they got up in the morning. On average, each person took two medicines. Many took more than three.
The researchers asked the other half to take at least one of their blood pressure medicines at bedtime.
They measured blood pressure by using 48-hour ambulatory monitoring at the start of the study -- not just a single daytime measurement used in most earlier studies. They also measured blood pressure three months after any treatment changes or, at the least, every year.
The researchers followed the men and women for about five and a half years. They looked to see which heart problems developed. They tracked death from any cause and from heart disease or stroke.They also tracked heart attack, angina, heart failure, and other problems.
More than half of those with chronic kidney disease also have high blood pressure, according to the National Kidney Foundation. High blood pressure increases the risk of the kidney disease worsening. Overall, one in three U.S. adults has high blood pressure, according to the researchers.
Bedtime Dosing of Blood Pressure Medicine
Those who took at least one blood pressure medicine at bedtime had lower nighttime blood pressure while asleep. They were also more likely to have overall good control of their blood pressure.
Improved overnight blood pressure with bedtime dosing had a real benefit. Each 5-point drop in sleep-time blood pressure was linked with a 14% reduction in risk for heart attack, stroke, or heart failure.
"Cardiovascular event rates in patients with hypertension can be reduced by more than 50% with a zero-cost strategy of administering blood pressure-lowering medications at bedtime rather than in the morning," Hermida says in a news release.
Why Blood Pressure Drugs Work Best at Bedtime
Hermida tells WebMD that some of the body's blood pressure control systems are most active while we sleep. So medicines designed to control those systems work better when taken close to the time when the systems are activated most fully.
The study results ''make absolute sense to me," says Robert Graham, MD, MPH, an internist and director of residency research at Lenox Hill Hospital. Graham, an assistant professor of medicine at New York University, reviewed the study findings for WebMD.
Graham has been prescribing blood pressure medicines to be taken at bedtime for years, he says, as it seems to help with the top side effects of blood pressure medicine: fatigue and drowsiness.
"If you do have high blood pressure, and have a hard time getting it [down to your] goal, maybe you should talk with your doctor about changing the time [you take the medicine]," he says.