Researchers examined data on 6,359 patients with at least one risk factor for cardiovascular events but no symptoms of cardiovascular disease at baseline. Participants had a mean age of 68.6 years at baseline, when they underwent 24-hour ambulatory blood pressure monitoring.
After a mean follow-up of 4.5 years, there were 306 cardiovascular events, including 119 strokes, 99 incidents of coronary artery disease, and 88 cases of heart failure.
Each 20 mmHg increase in nighttime systolic blood pressure was associated with an elevated risk of atherosclerotic cardiovascular disease (adjusted hazard ratio 1.18) and heart failure (aHR 1.25).
Compared with a normal circadian rhythm, a disrupted circadian rhythm with a "riser" pattern of nighttime blood pressure higher than daytime blood pressure was associated with increased risk of cardiovascular disease (HR 1.48) and heart failure (HR 2.45).
"During sleep, supine position increased the venous return from the lower body, resulting in increased preload of the heart," said lead study author Dr. Kazuomi Kario of Jichi Medical University School of Medicine in Tochigi, Japan.
"Thus, on the top of the increased preload, increased nighttime systolic blood pressure will extensively increase the cardiac wall strain by increase in both preload and afterload," Dr. Kario said by email.
In particular, the riser versus "dipper" pattern was associated with a significantly increased risk of total CVD (P=0.024) and HF (P=0.004), independent of office and 24-hour systolic blood pressure, the authors note in Circulation.
Among participants with well-controlled systolic blood pressure over 24 hours, individuals with disrupted diurnal blood pressure, or "extreme dippers," who experienced substantial decreases in nighttime blood pressure, had an increased risk of stroke (HR 1.61).
"In the era of heart failure after surviving stroke and coronary artery disease, antihypertensive strategy targeting nighttime blood pressure, and restoring disrupted circadian blood pressure variation should be an important and effective intervention," Kario said.
The majority of patients (76.7%) in the study took antihypertensive medications. For the baseline 24-hour blood pressure assessments, participants were instructed to follow usual activities, and to record what things they did and what times they went to sleep and woke up.
One limitation of the study is that researchers only examined 24-hour blood pressure at one point in time, and lacked data on any changes in ambulatory blood pressure at the time of any cardiovascular events, the authors note. The study also didn't look at diastolic measurements or include echocardiograms needed to differentiate specific types of heart failure.
"The take-home message is that we still don't know everything about the cardiovascular, stroke, and kidney consequences of having hypertension," said Dr. Raymond Townsend, a professor of medicine and director of the hypertension program at the University of Pennsylvania Health System in Philadelphia.
"There is a lot of room to improve how well we understand an individual's pressure-related risk through a better understanding of their blood pressure profile across the day and night," Dr. Townsend, who wasn't involved in the study, said by email.
For example, clinicians currently have little in the way of guidelines to inform what to prescribe, at what dose, and how to time to administer at night or in the morning or at both times of day when people have unusual nighttime blood pressure patterns, Dr. Townsend said.
"We understand that antihypertensive medications have been shown to save lives, hearts, brains and probably kidneys," Dr. Townsend said. "But we can still do even better in disarming hypertension."
By Lisa Rapaport
SOURCE: https://bit.ly/2JuOaOV Circulation, online November 2, 2020.
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