The type of blood pressure medicine that your doctor prescribes for you may not be as important as when you are taking it. Taking your blood pressure medication at bedtime instead of in the morning, or at other times during the day, appears to provide substantial benefits according to The Hygia Chronotherapy Trial, recently published in the European Heart Journal.
The study of more than 19,000 patients with high blood pressure, performed between 2008 and 2018, found that taking blood pressure medication at night lowered the risk of heart-related death and cardiovascular disease by nearly half. “The same medication ingested at different times of the day actually has different pharmacological properties, behaving like totally different medications,” said the study’s lead author, Ramón Hermida, director of the Bioengineering and Chronobiology Labs at the University of Vigo in Spain. 29, 201900:24
The study protocol randomly assigned half of the study participants to take their blood pressure medications upon waking in the morning. The other half was told to take their medications at bedtime. The researchers then followed the patients for approximately six years, while monitoring their blood pressure levels continuously over 48 hours, with an ambulatory blood pressure monitor, on at least a yearly basis.
Compared with the group who took their blood pressure medications in the morning, those who took the medications at bedtime had a 45 percent lower risk of experiencing a heart attack, heart failure, stroke, needing procedures to open clogged coronary arteries, or cardiovascular related death. In fact, their risk of dying from heart problems during the study period was cut by 56 percent. This finding was consistent regardless of the patient’s age, sex, blood pressure treatment upon entry into the study, cholesterol levels, or presence of pre-existing cardiovascular disease.
What might explain the findings in this study? In most people, blood pressure begins to rise in the early hours of the morning (around the time we wake) and reaches its peak around mid-day. It generally falls during sleep, reaching its lowest point between midnight and 3:00-4:00 am. This drop is sometimes called nocturnal “dipping” (usually dropping by 10-20%). But people who have high blood pressure are often found to have little or no decrease in their blood pressure at night.
Previous research has shown that having high blood pressure during sleep, being a “non-dipper”, and having only small differences between blood pressure readings during the day and night, are important risk factors for cardiovascular events. The study reports that while the impact on daytime blood pressure was similar, those assigned to take their medication at bedtime had a significantly greater decrease in blood pressure during sleep compared with those taking medication on waking, as well as a greater difference in blood pressure when sleeping compared with being awake.
While the findings are certainly encouraging, there are some caveats to consider. The study included only white participants, so it’s unclear whether the apparent benefits would be as effective other ethnic groups, such as African Americans. While most blood pressure medications are taken once a day, some are meant to be taken twice daily, so a morning dose would still be necessary. Additionally, some medications that lower blood pressure are prescribed for different clinical reasons, which may necessitate taking them during the day or in the morning. Certain kinds of blood pressure medications, such as diuretics, may not be convenient to take at night, because they increase urination.
The bottom line is that the same medications appear to have different effects if taken at a different point in time (a phenomenon known as “chronotherapy”). This difference appears to result in improved outcomes when blood pressure medication is taken at bedtime. It is important to discuss any changes that you would like to make with your prescribing physician.