Effects of caffeine differ in men and women

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Effects of caffeine differ in men and women

Last Updated: 2004-04-30 15:44:12 -0400 (Reuters Health)

By Alison McCook

NEW YORK (Reuters Health) - Researchers have long known that caffeine

increases blood pressure. Now, new findings show that this blood

pressure rise may occur for different reasons in men and women.

The investigators found that, in women, caffeine tends to raise blood

pressure by increasing the activity of the heart, causing it to pump

blood faster and raising so-called cardiac output. In contrast, caffeine

ups men's blood pressure by narrowing blood vessels, increasing the

resistance of blood vessels to the flow of blood.

Although caffeine appears to raise pressure for different reasons in men

and women, blood pressure increased by the same amount in both sexes,

suggesting that the potential health risks of caffeine are the same for

men and women, study author Dr. R. Lovallo told Reuters Health.

" Caffeine can increase blood pressure, and it can elevate pressure still

further when a person is under mental stress, " he said. " If you are

developing high blood pressure, or if you already have high blood

pressure, give up caffeine. "

During the study, Lovallo and his colleagues asked 42 premenopausal

women and 35 men of similar ages to take either an inactive pill or a

pill containing as much caffeine as 2 to 3 cups' worth of coffee. All

participants were in good health, had normal blood pressure and drank

coffee regularly.

To induce mental stress, the researchers then asked some of the people

who took caffeine to make a speech in front of a video camera and two

researchers wearing white coats.

The investigators found that caffeine raised blood pressure by the same

amount in men and women. However, men responded to the caffeine pills by

showing an increase in blood vessel resistance, with no change in

cardiac output. In contrast, women showed no change in vessel

resistance, and instead showed an increase in cardiac output, according

to the American Journal of Cardiology report.

Lovallo, who is based at the Veterans Affairs Medical Center and the

University of Oklahoma Health Sciences Center in Oklahoma City,

explained that previous research has established that caffeine tends to

increase blood pressure in men by increasing constriction of blood

vessels.

Although the reasons why women showed a different response are not

clear, researchers have shown that public speaking may provoke more

anxiety in women than in men, he noted.

" When women are experiencing anxiety, they may have greater increases in

how forcefully their hearts contract, in comparison to men. As a result,

caffeine may have intensified the anxiety and response of the heart in

the women, creating the difference in responses we saw, " Lovallo said.

SOURCE: American Journal of Cardiology, April 15, 2004.

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