So say British researchers who analyzed the link between blood pressure and cardiovascular death in a million adults. They found that during middle age every drop in systolic pressure (the top number) of 20 millimeters of mercury, and every 10 point decline in diastolic pressure (the lower figure) reduced the risk of deadly strokes, coronary artery disease and other vascular problems by more than 50 percent.
Somewhat surprisingly, lower blood pressure also helped the very elderly avoid cardiovascular deaths, though not by quite as much as in younger people. And the benefits weren't limited to people who brought their blood pressure down from unhealthy levels, according to the researchers, who report their findings in this week's issue of The Lancet.
"If the general population could all reduce their blood pressure by just a few millimeters of mercury, you could prevent about 10 percent of [fatal] strokes and 7 percent" of deadly coronary artery disease, says Sarah Lewington, an Oxford University epidemiologist and a co-author of the study. The coronary arteries are the plumbing for the heart, and they are vulnerable to plaque buildup that can deprive the organ of blood and trigger a heart attack.
Drugs, exercise and reduced salt intake, for certain people, can improve blood pressure, Lewington says.
An estimated one in four Americans has hypertension though a third don't know it, according to the American Heart Association. The condition, called the "silent killer," is the leading changeable cause of stroke in the United States, raising the risk sevenfold compared with people with normal blood pressure. High blood pressure is also a main source of kidney problems, which affect 8 million people in this country.
Lewington and her colleagues analyzed 61 previous studies of blood pressure and cardiovascular disease, which together included 1 million people. Of the 120,000 who died during the nearly 13 years of follow-up, 56,000 suffered fatal strokes, cases of deadly coronary artery disease, and other vascular mortality. Another 66,000 died of causes unrelated to the heart or vessels.
The researchers saw a protective effect of lower blood pressure until it hit about 115/75 mmHg, a low but fairly common reading.
"This study confirms what prior studies have been telling us for a long time, but in a much more powerful way," says Dr. Donald Lloyd-Jones, a researcher on the Framingham Heart Study and a cardiologist at Massachusetts General Hospital in Boston. "It is always better -- as long as it's not too low -- to have a lower blood pressure than a higher blood pressure in terms of your risk for cardiovascular disease."
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