Morning Blood Pressure Surge Linked to Stroke Risk

High blood pressure is diagnosed when a person’s systolic or top number is higher than 140 and a person’s diastolic pressure, or the bottom number, is greater than 90. Often patients undergo an ambulatory blood pressure, which is a 24-hour continuous blood pressure measurement. Researchers from Jichi Medical School in Japan conducted a study to see if surges in morning blood pressure rates were associated with stroke risk.

The study included 519 patients with high blood pressure who were followed for 41 months. All of the patients underwent ambulatory blood pressure monitoring and also had an MRI to determine which patients had a “silent” stroke. An indicator of silent stroke is a lesion on the brain that is detectable in an MRI.

Researchers determined the morning blood pressure surge by measuring the average systolic blood pressure during the two hours after waking up in the morning. They subtracted from that the average systolic blood pressure during one hour at night that included the lowest sleeping blood pressure. After determining these numbers, the participants were divided into two groups. One group included 53 patients who had a morning blood pressure surge increase of 55 millimeters of mercury or greater. The second group included the other 466 patients who had an increase less than 55 millimeters of mercury.

Authors say the participants who had the morning surge were more likely to have multiple “silent” strokes than the participants in the other group. Specifically, 57 percent in the first group had a silent stroke compared to 33 percent in the second group. Furthermore, 19 percent of those in the morning surge group suffered a stroke during the follow-up period compared to 7 percent in the second group. Researcher say even after adjusting for other factors including age and ambulatory blood pressure, the risk of stroke for people with a morning surge was nearly three times higher than for those without a morning surge.

In an accompanying editorial, Norman Kaplan, M.D., from UT Southwestern Medical Center in Dallas, says this research is clear that there is a connection between morning surge of blood pressure and stroke risk. He says it would be logical for drug treatment to include antihypertensive medicines that are effective for 24 hours or longer.