March 25, 2002
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Coffee Raises Blood Pressure, Though Not by Much  

There's good news and bad news for java junkies. Modest coffee drinking is associated with a small increase in blood pressure, Johns Hopkins investigators say, but it's probably not enough to substantially increase your risk of hypertension.

In a long-term study of more than 1,000 men, drinking a daily cup of regular coffee raised systolic pressure (the upper number) by 0.19 mmHg and diastolic blood pressure (the lower number) by 0.27 mmHg. Coffee drinkers also had a greater incidence of hypertension (28 percent) than their non-coffee drinking counterparts (19 percent).

Results of the study, published in the March 25 issue of the Archives of Internal Medicine, also showed that those who drank five or more cups of coffee a day were up to 1.6 times more likely to develop hypertension than non-coffee drinkers, although these associations were less significant after the researchers took into account alcohol intake, smoking and other characteristics associated with coffee drinking.

"Overall, coffee drinkers had higher blood pressures than people who did not drink coffee, but there was no set ‘dose-response' relationship," says Michael J. Klag, M.D., M.P.H., lead author of the study and director of the Division of General Internal Medicine at Hopkins. Still, Klag says people who already have high blood pressure should reduce their coffee intake because other studies have clearly shown that avoiding caffeine-containing drinks can lower blood pressure.

The research team analyzed data from the Johns Hopkins Precursors Study, a long-term study of male medical students who enrolled at Hopkins between 1948 and 1964 and who continue to be followed. In medical school and through the follow-up period, information on family history and health behaviors has been collected.

For this report, coffee intake, blood pressure and presence of hypertension were assessed in 1,017 white males during school and up to 11 additional times over an average follow-up of 33 years. At the study's start, the men were young (average age 26), were at a healthy weight, and had desirable blood pressure and cholesterol levels. Coffee intake was assessed during medical school, every five years after graduation until 1984, and in 1978, 1986, 1989 and 1993. After 1986, participants were asked about caffeinated coffee. Blood pressure and incidence of hypertension were determined annually through mailed surveys.

Overall, 82 percent of the participants reported they drank an average of two cups of coffee daily. Coffee drinkers were more likely to drink alcohol and to smoke cigarettes. During the follow-up period, 281 men developed hypertension around age 53. By age 60, the incidence of hypertension (28 percent) was greater among men who drank coffee in medical school than in those who did not (19 percent). Risk of hypertension was slightly greater in those drinking three or four cups a day compared with those who abstained.

The majority of coffee drank most likely was percolated and unfiltered, Klag says.
"The coffee we drink today is probably a little healthier than what this population consumed, since coffee filters didn't come into widespread use until after 1975," he says. "Passing boiled coffee through a paper filter removes terpenes – chemical particles that raise cholesterol."

The study was supported by the National Institute on Aging, a division of the National Institutes of Health. Other authors were Nae-Yuh Wang, Ph.D.; Lucy A. Meoni, Sc.M.; Frederick L. Brancati, M.D., M.H.S.; Lisa A. Cooper, M.D., M.P.H.; Kung-Yee Liang, Ph.D.; J. Hunter Young, M.D., M.H.S.; and Daniel E. Ford, M.D., M.P.H.

Klag, M.J. et. al., "Coffee Intake and Risk of Hypertension," Archives of Internal Medicine, March 25, vol. 162, pp. 657-662.

Related Links:
Johns Hopkins' Welch Center for Prevention, Epidemiology and Clinical Research

American Medical Association


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