For people who have had a stroke and survived, there is always the threat of another one. The good news is that stroke survivors can cut their risk of a second event in half by consistently keeping their blood pressure under control.

Lowering your blood pressure is good of course, but it appears that keeping good control of your pressure is important, too, according to a new study.

“Fluctuations in blood pressure may be associated with greater cardiovascular risk,” Amytis Towfighi, M.D., lead author and assistant professor of neurology at the Keck School of Medicine at the University of Southern California, said in a statement.

“It's not enough to control blood pressure some of the time. Averages do not take into account variability in blood pressure readings from one check to the next.”

To help patients maintain consistent control of blood pressure, some changes may be needed.

Researchers looked at results from the Vitamin Intervention for Stroke Prevention (VISP) trial, which involved over 3600 ischemic stroke patients age 35 and older. Ischemic Stroke are those caused by a clot or other blockage in a blood vessel supplying the brain.

People enrolled in that trial had had their blood pressure levels taken at the start of the study, a month later, at six months and every six months for up to 24 months thereafter.

The researchers in the current study found that fewer than 30 percent of stroke survivors studied maintained consistent blood pressure control more than 75 percent of the time. Blood pressure was considered "controlled" at 140 mm Hg over 90 mm Hg or lower.

Those who did keep their blood pressure under control were rewarded with a greatly reduced risk of having another stroke.

Stroke survivors with high blood pressure at the first baseline pressure check (systolic blood pressure over 153 mm Hg) and who were able to keep their blood pressure under control more than 75 percent of the time, had a second stroke rate that was 54 percent lower than those who kept their blood pressure under control less than 25 percent of the time.

People with a history of heart attacks were among the most likely to keep their blood pressure under control more consistently. It may be that patients and healthcare practitioners are more aware of controlling blood pressure after heart attack but less diligent after stroke.

The key for stroke survivors is to pay close attention to their blood pressure, monitoring it often, and to pursue regimens that lower blood pressure — reducing salt intake, eating a healthy diet (rich in whole grains, fruits and vegetables) and exercising regularly.

“One of the things we really emphasize is getting patients involved in their own care, and learning how to control their risk factors,” Towfighi said. To help patients maintain consistent control of blood pressure, some changes may be needed, she added. Rather than check blood pressure only during clinic visits, it should be done more regularly, perhaps at home by machines that can remotely transmit the data.

Most concerning is the low percentage of trial participants controlling their blood pressure from one check to the next. As Towfighi put it, “you can only imagine how poor blood pressure control is outside of the clinical trial setting.”

The study is published in the American Heart Association journal, Stroke.