TOCHIGI, Japan — People who have high blood pressure while asleep are more likely to suffer cardiovascular disease, especially heart failure, in the future, a new study reveals. In fact, researchers at Jichi Medical University in Japan warn that even when a patient’s daytime blood pressure is within normal ranges, they are still more likely to have a heart attack or a stroke.
Medical practitioners typically use in-office and daytime blood pressure measurements to determine a patient’s hypertension medication needs and dosages. But many patients may have undetected high blood pressure while sleeping, also known as nocturnal hypertension, scientists say.
“Nighttime blood pressure is increasingly being recognized as a predictor of cardiovascular risk,” says lead author Professor Kazuomi Kario, a professor of cardiovascular medicine, in a statement to the American Heart Association. “This study provides much more in-depth information about the cardiovascular risk associated with high nighttime blood pressure and different nighttime blood pressure phenotypes than have been reported previously.”
Patients’ blood pressure monitored during the day and while sleeping
For the study, data was collected from 6,359 adults from across Japan between 2009 and 2017. Nearly half of the study participants were male, and more than half were at least 65 years old. The patients all had at least one cardiovascular risk factor, and three-quarters of them were taking blood pressure medications. None had symptomatic cardiovascular disease when the study began.
Researchers measured daytime and nighttime blood pressure levels using an at-home, wearable monitor. Measurements were taken for at least 24 hours at a time, and device data were periodically downloaded at a health care clinic. Participants were instructed to self-report their daily activities along with sleep and wake times in a diary. A
Almost every participant recorded 20 daytime and seven night-time automated blood pressure measurements. Follow-ups occurred annually via phone or clinic visit, with total follow up ranging from two to seven years.
Researchers analyzed the rates of cardiovascular disease events, including heart attacks, strokes, heart failure and death, among the participants. The occurrence and timing of heart events in relation to blood pressure variations was analyzed to determine whether there were any associations.
In all, participants experienced a total of 306 cardiovascular events, including 119 strokes, 99 diagnoses of coronary artery disease, and 88 diagnoses of heart failure.
‘Significant, independent risk factor for cardiovascular events’
Authors say that an abnormal reading, or a systolic blood pressure measuring 20 mm Hg above a person’s daytime systolic reading, is significantly linked to the risk of atherosclerotic cardiovascular disease and heart failure. Similarly, participants with an abnormal circadian pattern, which occurs when sleep blood pressure exceeds daytime readings, were at particular risk of developing heart failure and had a greater risk of experiencing any heart disease event.
Excessive reduction of blood pressure during sleep may also be detrimental. Patients with well-controlled hypertension showed a significantly increased risk of stroke when nighttime systolic pressure took extreme dips.
“Results indicate that nighttime systolic blood pressure was a significant, independent risk factor for cardiovascular events,” says Kario. “The study highlights the importance of including nighttime blood pressure monitoring in patient management strategies and will hopefully encourage physicians to ensure that antihypertensive therapy is effectively lowering blood pressure throughout the 24-hour dosing period.”
But the authors note that their study is not without limitations.
Ambulatory data were obtained once at the start of the study. However, no information was available regarding the contributions of subsequent changes in ambulatory blood pressure levels up until the time of diagnosis of a cardiac event. The study also focused on systolic, rather than diastolic, measurements due to the older age of the participants.
The authors say study evaluations did not include echocardiograms, thus preventing some degree of differentiation for types of heart failure.
The new research is published in the American Heart Association’s flagship journal Circulation.