Blood Pressure Even More Strongly Associated with Cardiovascular Mortality than Previously Believed
Blood pressure is the pressure exerted by blood against the walls of arteries. It is expressed as systolic pressure , measured when the heart beats, over diastolic pressure , measured when the heart relaxes between beats. Traditionally, blood pressure is considered normal when it falls below 140/90 mmHg.
Several studies have shown that as blood pressure rises, so does the risk of death from cardiovascular causes. But there has been some disagreement, for example, on whether or not this risk continues to fall as blood pressure moves below 140/90 mmHg, or on the association between blood pressure and disease risk in older people.
In a meta-analysis published in The Lancet , researchers found that higher blood pressure is associated with higher cardiovascular mortality, even within the normal range; that this relationship is stronger than previously thought; and that blood pressure has a greater impact on cardiovascular mortality in people in their 70s and 80s than has been estimated in the past. This meta-analysis adds a great deal to the existing research because it analyzed data from close to one million people, and excluded people with pre-existing vascular disease.
About the Study
Researchers analyzed data from 61 prospective, observational studies that examined blood pressure and mortality, and involved 958,074 participants. Studies were excluded from the meta-analysis if they included participants with a history of stroke or heart disease.
The researchers were interested in finding an association between the risk of death during five decades of age (40–49, 50–59,…,80–89 years) and the estimated blood pressure at the start of that decade.
Of the 958,074 participants, approximately 122,000 died over the course of their respective studies.
The causes of death were:
- Vascular deaths (56,000)
- Nonvascular deaths (66,000)
Blood Pressure and Stroke Mortality
The researchers found a strong, direct relationship between blood pressure and stroke mortality at all ages. Between the ages of 40 and 69, each blood pressure increase of 20 mm Hg systolic or 10 mm Hg diastolic was associated with a more than twofold increase in the stroke death rate. This held true down to a blood pressure of 115/75 mm Hg, which is considered to be in the “optimal” range. The strength of the association declined a bit after age 70, but because stroke is so much more common in old age, the relationship remains important.
Blood Pressure and Ischemic Heart Disease Mortality
There was a strong, direct relationship between blood pressure and ischemic heart disease mortality at all ages. Again, each 20 mm Hg difference in systolic pressure or 10 mm Hg difference in diastolic pressure corresponded to about a twofold difference in ischemic heart disease mortality down to optimal blood pressure, throughout middle age. The relationship is also strong in old age.
Blood Pressure and Other Vascular Mortality
A 20 mm Hg difference in systolic blood pressure was associated with a fourfold difference in mortality from hypertensive heart disease, and a twofold difference in mortality from other serious vascular diseases including ]]>heart failure]]> , ]]>aortic aneurysm]]> , ]]>atherosclerosis]]> , and sudden death.
Blood Pressure and Non-vascular Mortality
A 20 mm Hg reduction in systolic blood pressure lowered the risk of non-vascular death by 12%.
In calculating these results, researchers adjusted for known factors that could contribute to cardiovascular mortality other than blood pressure: total blood cholesterol, lipid fractions (HDL and non-HDL cholesterol), diabetes, weight, alcohol consumption, and smoking.
How Does This Affect You?
This meta-analysis clearly shows that for people of all ages, lowering blood pressure levels—even levels that are in the normal age—can significantly reduce risk of cardiovascular death as well as overall mortality. The researchers commented that a 10 mm Hg reduction of systolic blood pressure or a 5 mm Hg reduction of diastolic blood pressure could, in the long term, be associated with a 40% lower risk of stroke death and a 30% lower risk of death from ischemic heart disease or other vascular causes throughout middle age.
With that kind of incentive, the only question remains how to go about lowering your BP. The first step is to determine what category your blood pressure falls into.
For those with blood pressure in the normal range, it may be possible to further reduce your blood pressure with the following lifestyle changes:
- Follow the DASH diet]]> , one that is rich in fruits and vegetables and low-fat dairy products, and low in saturated fat, total fat, and cholesterol. The DASH diet has been shown to significantly reduce blood pressure.
- Exercise regularly.
- Maintain a healthy weight; lose weight if necessary.
- If you smoke, quit.
- Drink alcohol in moderation. That means no more than two drinks per day for men and one drink per day for women.
If you already have high blood pressure, you might want to supplement these lifestyle changes with stress management. Medication may become necessary if lifestyle changes are not effective.
The main categories of drugs used to treat high blood pressure are:
American Heart Association
National Heart, Lung, and Blood Institute
National Institutes of Health
Prospective Studies Collaboration. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. The Lancet . 2002;360:1903-1913.
Last reviewed Dec 19, 2002 by ]]>Richard Glickman-Simon, MD]]>
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