Study finds lower systolic blood pressure reduces risk of stroke

People 60 or older, especially minorities and women, have a lower risk of stroke if the top number (systolic) in their blood pressure is below 140 millimeters of mercury (mm Hg), according to a study conducted by a team of neurologists at the University of Miami Miller School of Medicine and Columbia University.

The findings, presented at the American Stroke Association's International Stroke Conference 2015 in Nashville, challenge a controversial report published recently in the Journal of the American Medical Association.

The JAMA report advised doctors to aim for blood pressure readings of less than 150/90 mm Hg when treating patients 60 or older who do not have diabetes or chronic kidney disease. That raised the standard for systolic blood pressure by 10 points from previous guidance, stirring controversy among healthcare providers, agencies and professional groups.

The 2014 report relied on evidence from clinical trials, but did not consider data from various other studies that support a systolic blood pressure goal of less than 140 for these patients, said Chuanhui Dong, Ph.D., lead author of the new study and research associate professor at the Miller School.

The new study involved 1,706 people older than 60 (average age 72) in the Northern Manhattan Study in New York City, funded by the National Institute of Neurological Disorders and Stroke at the National Institutes of Health. None of the participants had a previous stroke, diabetes or kidney disease. After adjustment for age, sex, race/ethnicity and use of blood pressure medications, stroke risk was 70 percent higher for people with systolic pressure in the 140-149 range, compared with those whose readings fell below 140.

The results support what some health experts had feared, Dong said. "Raising the treatment bar could lead to more strokes."

The study found that the elevated stroke rate for people in the 140-149 range is close to the 80 percent higher risk found for people with systolic readings at or above 150.

"Our study results do not support the Joint National Committee recommended change of systolic blood pressure control level from 140 to 150," said Ralph L. Sacco, M.D., M.S., professor and Chairman of Neurology and Olemberg Family Chair in Neurological Disorders at the Miller School. "Data from our Northern Manhattan Study clearly show that BP from 140-149 among people without chronic kidney disease or diabetes is just as risky for stroke as BP greater than 150."

Among people in the study, 20 percent had systolic readings of 140-149, and 37 percent had readings of 150 or greater. About 40 percent of the subjects were taking blood pressure medicine.

Compared with those whose readings were below 140, the study found measurable differences in those with systolic readings of 140-149: Hispanics had 2.4 times the risk of a first stroke and blacks had twice the risk. No such difference was seen in non-Hispanic whites, but their numbers in the study were too small for firm conclusions to be drawn, according to the researchers.

Dong said healthcare providers should heed the findings because Hispanics and blacks are known to suffer strokes more frequently than whites.

Women in the study with a systolic pressure of 140-149 faced nearly double the risk of a first stroke, compared with those below the 140 threshold. Men in the 140-149 range had a 34 percent higher risk.

Sacco said, "Hypertension remains the strongest modifiable risk factor for stroke and better BP control is beneficial for reducing stroke risk and improving brain health." Dong added, "Reduction in systolic blood pressure below 140 is important in primary stroke prevention, even among those over 60 without diabetes or chronic kidney disease."

Co-authors of the study are Tatjana Rundek, M.D., Ph.D., professor of neurology and Chief of Neurology Clinical and Translational Research, and Clinton B. Wright, M.D., M.S., associate professor of neurology and Director of the Division of Cognitive Disorders at the Miller School. Columbia University co-authors are Mitchell S. V. Elkind, M.D., M.S., M.Phil., professor of neurology and epidemiology, and Chensy Marquez, research assistant in neurology.

Strengths of the research include its real-world population, the fact that few people dropped out, and a high proportion of Hispanics from the same community. The sample size for whites and blacks was relatively small, however, limiting the study's ability to discern differences in risk among groups.