Morning surge in blood pressure linked to strokes in elderly

In older people with high blood pressure, a sharp increase in blood pressure in the morning increases the risk of stroke and is linked to brain lesions known as “silent” strokes, according to a study in today’s rapid access issue of Circulation: Journal of the American Heart Association. “This study is the first to show that an excessive morning blood pressure surge is a predictor of stroke in elderly people with high blood pressure,” says lead author Kazuomi Kario, M.D., from the department of cardiology at Jichi Medical School in Tochigi, Japan. From the American Heart Association:
Morning surge in blood pressure linked to strokes in elderly

DALLAS, March 4 ? In older people with high blood pressure, a sharp increase in blood pressure in the morning increases the risk of stroke and is linked to brain lesions known as “silent” strokes, according to a study in today’s rapid access issue of Circulation: Journal of the American Heart Association.

“This study is the first to show that an excessive morning blood pressure surge is a predictor of stroke in elderly people with high blood pressure,” says lead author Kazuomi Kario, M.D., from the department of cardiology at Jichi Medical School in Tochigi, Japan. “This finding was independent of ambulatory blood pressure levels and target organ damage.”

Ambulatory blood pressure is a 24-hour continuous blood pressure measurement. Target organ damage is the damage to organs such as the brain, heart or kidneys caused by high blood pressure.

“This study also extends previous work showing that people with an extreme dip in blood pressure overnight are at increased risk for stroke, and that the reason may be the morning surge rather than the excessively low blood pressure during the night,” Kario says.

Kario’s team followed 519 Japanese patients with high blood pressure (average age 72) for an average of 41 months. All participants underwent ambulatory blood pressure monitoring and a magnetic resonance imaging (MRI) scan to determine the presence of silent cerebral infarcts (brain lesions that indicate a “silent” stroke). High blood pressure (hypertension) is diagnosed when average systolic pressure (the top number in a blood pressure reading) is 140 millimeters of mercury (mmHg) or greater, or average diastolic pressure (bottom number) is 90 mm Hg or greater.

Researchers calculated the morning blood pressure surge by measuring the average systolic blood pressure during the two hours after awakening, and subtracting the average systolic blood pressure during the one hour that included the lowest sleeping blood pressure.

Participants were divided into two groups. The morning surge (MS) group included 53 patients who had a morning blood pressure increase of 55 mm Hg or greater. The non-MS group included the remaining 466 patients who had a morning blood pressure increase of less than 55 mm Hg. The average morning blood pressure increase was 69 mm Hg in the MS group, and 29 mm Hg in the non-MS group.

The researchers found that participants in the MS group were more likely to have multiple “silent” strokes (57 percent) than the non-MS group (33 percent) according to their MRIs at the start of the study. In addition, 19 percent of those in the MS group had a stroke during the follow-up period compared with 7.3 percent of people in the non-MS group.

Even after adjusting for age and ambulatory blood pressure, the relative risk of stroke for people with a morning surge was nearly three times higher than for people without the surge. Researchers also found that a 10 mm Hg increase in the morning blood pressure surge increased stroke risk by 22 percent.

Kario says, “The results suggest that the morning surge in blood pressure could be a new target for drug treatment to prevent target organ damage and subsequent stroke in patients with high blood pressure.” He adds that even though the study was not designed to investigate the effect of blood pressure-lowering medication on stroke risk, they did observe that such medication was associated with reduced stroke risk.

“Thus, controlling the morning surge with antihypertensive medication might decrease stroke risk,” Kario says.

He adds that these findings should be investigated in other populations and in a large randomized, controlled trial using antihypertensive drugs aimed at suppressing the morning blood pressure surge.

In an accompanying editorial, Norman M. Kaplan, M.D., from the University of Texas Southwestern Medical Center at Dallas, quips, “Some days it just doesn’t pay to get out of bed.”

He says Kario’s study is the largest and most definitive investigation of the long-recognized pattern of higher cardiovascular event rates in the morning hours.

“The clinical inferences of the data from this study are clear,” Kaplan says. “Patients who experience surges of blood pressure after arising are at risk for stroke and likely other cardiovascular events. The presence of such surges can be identified by home blood pressure measurements. And, if the early morning blood pressure is above 140/90 mm Hg, additional antihypertensive therapy is indicated.”

He adds that it would be logical for drug treatment to include antihypertensive medicines that are effective for 24 hours or longer.

Kario’s co-authors are Thomas G. Pickering, M.D.; Yuji Umeda, M.D.; Satoshi Hoshide, M.D.; Yoko Hoshide, M.D.; Masato Morinari, M.D.; Mitsunobu Murata, M.D.; Toshio Kuroda, M.D.; Joseph E. Schwartz, Ph.D.; and Kazuyuki Shimada, M.D.

This research was partly funded by the National Heart, Lung, and Blood Institute.

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