Prehypertension Leads to Increased Hospitalization and Early Death
Fifty million people in the United States have hypertension, or ]]>high blood pressure]]> , which increases a person’s risk for cardiovascular disease including ]]>heart attack]]> and ]]>stroke]]> . Despite its potentially serious consequences, only about 34% of people with hypertension control it adequately. In 2000, hypertension was responsible for approximately 215,000 deaths.
Until May 2003, anyone with a blood pressure reading of less than 130/90 millimeters of mercury (mm Hg) was considered to have normal blood pressure. But then the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (the JNC 7 Report) issued recommendations classifying a person with a systolic blood pressure (top number) of 120–139 mm Hg or a diastolic blood pressure (bottom number) of 80–89 mm Hg as prehypertensive .
One reason for this new classification was the finding that people who are prehypertensive are more likely to develop hypertension than those with lower blood pressures. But does prehypertension carry its own risks of complications?
A study published in the October 25, 2004 Archives of Internal Medicine found that prehypertension contributes to a substantial number of hospital and nursing home admissions and premature deaths. Another study, published in the same issue of Archives , found that people with prehypertension are more likely than people with normal blood pressures to have additional risk factors for heart disease and stroke.
About the Study
In the first study, researchers created a simulation model to estimate the number of hospital and nursing home admissions and deaths attributable to prehypertension and residual hypertension , a term used to describe people who attempted to control their hypertension with medication, but still had systolic blood pressures ≥ 140 mm Hg.
The researchers used data from The National Health and Nutrition Examination Survey I (NHANES I) as the basis of their simulation model. NHANES I collected information about health risk factors from representative samples of Americans from 1971 to 1975, then followed them for twenty years to track hospitalizations, nursing home admissions, and deaths. The simulation model was then applied to data collected from 12,841 adults, aged 25 to 74, from 1988 to 1994 for NHANES III. The researchers used NHANES III data because the distribution of risk factors (more people who were obese and fewer smokers, for example), more closely reflected risk factors in today’s population.
To estimate the effects of eliminating residual hypertension, the researchers ran their model with the initial NHANES III data and then again after identifying everyone with a systolic blood pressure of 140 mm Hg or higher and resetting that value to 139 mm Hg (in effect, “lowering” their high blood pressure). The difference between the baseline model and the adjusted model reflected the effect of eliminating residual hypertension.
Next, researchers estimated the effects of eliminating prehypertension and residual hypertension by following the same procedure, but identifying everyone with a systolic blood pressure of 120 mm Hg or higher and replacing it with a systolic blood pressure of 119 mm Hg.
To gauge the effects of eliminating only prehypertension, the researchers subtracted the effects of eliminating residual hypertension from the effects of eliminating residual hypertension and prehypertension.
The results were broken down according to gender and age groups: 25 to 44, 45 to 64, and 65 to 74 years.
In the second study, researchers analyzed medical data from 3488 people aged 20 and older, which was collected for NHANES from 1999–2000. The study participants were classified into three blood pressure categories:
Normal (<120/80 mm Hg)
Prehypertensive (120-139/80-89 mm Hg)
Hypertensive (≥140/90 mm Hg)
The researchers also noted whether the study participants had high cholesterol (more than 240 mg/dL [6.2 mmol/L] or use of cholesterol-lowering medication), above-optimal cholesterol (200–239 mg/dL [5.2-6.1 mmol/L]); were overweight (body mass index or BMI≥25) or obese (BMI≥30); had type 2 diabetes; or were smokers.
More than one-third of every age/gender group, except women aged 25 to 44 years, had prehypertension. Two-thirds of men and women aged 45 to 64 years, and 80% of men and women aged 65 to 74 years had either residual hypertension or prehypertension.
After running the simulation model, the researchers found that for every 10,000 people, eliminating residual hypertension would lower hospital admissions by 1.3%, nursing home admissions by 3.2%, and deaths by 4.6% in the first year. Eliminating both residual hypertension and prehypertension would reduce hospital admissions by 4.7%, nursing home admissions by 9.7%, and deaths by 13.7%.
The elimination of prehypertension alone had a strong impact. Prehypertension accounted for 3.4% of hospital admissions, 6.5% of nursing home admissions, and 9.1% of deaths for every 10,000 people.
Women aged 65 to 74 years benefited most from eliminating residual hypertension and prehypertension, followed by men aged 45 to 64 and 65 to 74 years.
Researchers from the second study found that 39% of study participants had normal blood pressure levels, 31% were prehypertensive, and 29% had hypertension.
The study showed that people with prehypertension were 1.65 times as likely as people with normal blood pressure to have at least one risk factor for heart attack and stroke. They were significantly more likely to have above-optimal cholesterol levels or to be overweight or obese than people with normal blood pressures. People with prehypertension were also more likely (but not significantly so) to have type 2 diabetes, but were less likely than people with normal blood pressures to be smokers.
How Does This Affect You?
These studies showed that people with prehypertension are more likely to have other cardiovascular (CVD) risk factors, and are at an increased risk for hospital and nursing home admissions and early death. However, no clinical trials have shown that treatment of prehypertension—either through lifestyle changes or with the use of medication—effectively eliminates these risks or prevents these outcomes.
But prehypertension is often part of what the JNC 7 report refers to as a “lifestyle syndrome”—characterized by a group of coexisting conditions including high cholesterol and type 2 diabetes—that is in large part the result of consuming too many calories and not getting enough physical activity.
So rather than focusing on prehypertension, it might be better to aim for a healthy lifestyle based on good nutrition and regular exercise. This approach should help prevent not only prehypertension, but also many of the other CVD risk factors associated with it.
American Heart Association
National Heart, Lung, and Blood Institute
National Institutes of Health
Daviglus MI et. al. Today’s agenda: we must focus on achieving favorable levels of all risk factors simultaneously. [Editorial]. Arch. Int. Med. 2004; 164: 2086-2087.
Greenlund KJ et. al. Prevalence of heart disease and stroke risk factors in person with prehypertension in the United States, 1999-2000. Arch. Int. Med. 2004; 164: 2113-2118.
Russel LF et. al. Effects of prehypertension on admission and deaths: a simulation. Arch. Int. Med. 2004; 164: 2119-2124.
Last reviewed Oct 29, 2004 by ]]>Richard Glickman-Simon, MD]]>
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