Coffee Doesn't Increase Hypertension Risk, at Least for Women

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Coffee Doesn't Increase Hypertension Risk, at Least for Women



By , MedPage Today Staff Writer

Reviewed by Rubeen K. Israni, M.D., Fellow, Renal-Electrolyte and

Hypertension Division, University of Pennsylvania School of Medicine

Source News Article: Forbes, MSN, MSNBC

MedPage Today Action Points

Explain to patients that the caffeine in coffee causes increases in

heart rate and blood pressure soon after it is drunk.

Point out to patients that this study shows those acute rises do not

increase the risk of long-term hypertension.

Review

BOSTON, Nov. 9 - Starbucks take note. Contrary to popular belief and

clinical lore, there's no link between hypertension and coffee intake

for women.

On the other hand, there is an unexpected association between cola

beverages and high blood pressure, says Wolfgang Winkelmayer, M.D.,

of Brigham and Women's Hospital here.

The findings come from an analysis of high blood pressure and

caffeine intake in the two Nurses Health Studies (NHS), Dr.

Winkelmayer and colleagues reported in the Nov. 9 issue of the

Journal of the American Medical Association. Men were not studied.

The researchers looked at 155,594 women in the two prospective cohort

studies who were free of hypertension at baseline. Over a 12-year

follow-up, 19,541 women in NHS I developed with hypertension and

13,536 were diagnosed in NHS II.

The researchers looked at the association of caffeine intake with

hypertension after adjusting for age, body mass index, alcohol

intake, family history of hypertension, physical activity, and

smoking status.

When the researchers looked at total caffeine intake -- including

everything from coffee to cola to chocolate -- they found an odd

result, Dr. Winkelmayer said. Women whose intake was lowest had the

same risk of developing hypertension as those who had the highest

intake, while those with a moderate consumption had elevated risk.

" This was a little bit of a surprise finding, " he said. " We took a

step back and said we have to deconstruct this result. "

When they looked at coffee itself, he said, there was " no distinct

and positive association " between coffee and hypertension.

In fact, there might even be a slight protective effect -- at the

highest intake (of more than six cups of coffee a day), the odds

ratios for hypertension were 0.88 (95% CI 0.80-0.98) and 0.91 (95% CI

0.80-1.04), for NHS I and II, respectively, compared with the lowest

intake of less than one cup a day. Furthermore, the risk of

developing hypertension decreased as coffee consumption increased

from less than 1 cup to greater than 6 cups (test for trend showed

p=0.02 and p=0.03 respectively for the two NHS cohorts).

When the researchers looked at tea drinkers, the results were

inconclusive.

But when they turned their attention to cola beverages, they saw " the

second surprise of our study -- that we found a very consistent,

direct, and positive association between cola drinks and the risk of

hypertension, " he said.

In fact, the study showed:

In NHS I, women who drank sugared cola had a linear increase in risk,

reaching an odds ratio of 1.44 for the highest intake -- four or more

cans a day -- compared to the lowest (less than one can a day).

The same pattern was seen for women in NHS I who drank sugar-free

cola, with the odds ratio reaching 1.16 at the highest intake. (In

both cases, the 95% confidence intervals crossed one, but the p-

values for trend were 0.03 and 0.02, respectively.)

For NHS II, the researchers found the same pattern:

Women who drank more than four cans a day of sugared cola had an odds

ratio of 1.28 compared to the reference group, with the 95%

confidence interval ranging from 1.01 to 1.62.

Women who drank the most sugar-free cola had an odds ratio of 1.19

compared to the women who drank the least, with the 95% confidence

interval ranging from 1.08 to 1.32.

Exactly why cola should be linked to hypertension in women remains

unclear, Dr. Winkelmayer said.

" We have no clue what biological mechanism ties cola consumption to

high blood pressure, " he said, so it's premature to suggest that

women cut down on their beverages.

The effects of coffee consumption in men have not been studied in

such a large group of subjects, he said, although a 2002 study in

Archives of Internal Medicine examined a cohort of 1,017 men.

Over several years of follow-up, that study found, coffee contributed

to small increases in blood pressure, but did not appear to play a

role in the development of hypertension.

Primary source: Journal of the American Medical Association

Source reference:

Winkelmayer WC et al. Habitual Caffeine Intake and the Risk of

Hypertension in Women. JAMA. 2005;294:2330-2335.

Additional source: Archives of Internal Medicine

Source reference:

Klag MJ et al. Coffee intake and risk of hypertension: the Hopkins

precursors study. Arch Intern Med. 2002;162:657-662.