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March 4, 2003

Popular hypertension drug does not increase cholesterol in healthy patients

UW/Group Health study debunks myth that thiazide diuretics usually increase bad cholesterol

Seattle—Hydrochlorothiazide (HCTZ)—a widely used and inexpensive high-blood-pressure drug once suspected of having bad effects on blood cholesterol—actually poses no such threat when given in low doses to healthy adults, according to researchers from the University of Washington and Group Health Cooperative.

That's good news for individuals at risk for multiple health problems, including osteoporosis. Previous studies by the same research team showed that, in addition to lowering high blood pressure, HCTZ lowered patients' risk of hip fractures and increased their bone mineral density.

Still, many physicians have been hesitant to prescribe HCTZ and other similar "thiazide diuretics" to some patients because of long-held beliefs that these drugs could increase the amount of harmful cholesterol in the blood, leading to cardiovascular problems. But this new study—conducted over a three-year period among 320 Group Health members aged 60 to 79—offers reassurance that the drug, when used in low doses by healthy patients, does not lead to increased risk.

Why was the link between thiazide diuretics and cholesterol a concern in the first place? Some past studies of higher doses of the drugs failed to significantly decrease the incidence of coronary artery disease events, explains Susan M. Ott, MD, professor of medicine at the University of Washington and the lead author of the study. This led some investigators to suggest that thiazide diuretics worsen coronary artery disease by causing adverse changes in blood cholesterol levels. However, nearly all these studies had been conducted among people with high blood pressure.

But this new study, released today in the Journal of the American Geriatrics Society, was the largest long-term study of thiazide diuretics among patients with normal blood pressure. While high doses of thiazides can increase bad cholesterol, said Ott, this study showed that 12.5 milligram and 25 milligram doses had minimal effects on cholesterol metabolism in healthy older adults.

Ott said the findings are important in light of recent research showing the harmful effects of estrogen, which many women had been taking to prevent hip fractures. "We need to find a safe, gentle drug that can be taken over a long period of time to stop bone loss," said Ott. "More studies are needed to learn the long-term effects of thiazides, but this study shows that it's certainly a candidate."

Andrea LaCroix, PhD, senior investigator at Group Health's Center for Health Studies, and co-author of the study, agrees. "The goal of our research has been to look at these medications and see how they affect multiple conditions in older people like osteoporosis and heart disease," she said. "I think it's very reassuring to find that one of the least expensive and most effective drugs for lowering blood pressure in older people is also one of the safest and well tolerated."

About Group Health Center for Health Studies
Group Health Center for Health Studies conducts epidemiologic, health-services, and clinical research related to prevention, diagnosis, and treatment of major health problems. Funded primarily through government and private research grants, the Center is located in Seattle, Washington.

Group Health is a consumer-governed, nonprofit health care system that coordinates care and coverage. Based in Seattle, the Cooperative serves nearly 600,000 members in Washington and Idaho.

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