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Heavy smoking with Pill use ups heart attack risk

April 25, 2001

NEW YORK (Reuters Health) - Women who use oral contraceptives (OC) and smoke heavily are at increased risk of having a first heart attack, study findings indicate.

But nonsmokers and light smokers who take low-dose birth control pills do not appear to be putting themselves at risk, Dr. Lynn Rosenberg of Boston University School of Public Health in Brookline, Massachusetts, and colleagues report.

Their study in the April 23rd issue of the Archives of Internal Medicine investigated the link between the new low-dose birth control pills and smoking among women under the age of 45.

Previous studies have found that older birth control pills, which contained higher levels of estrogen, raised a woman's risk of heart attack, particularly if she smoked heavily. In the current study, low-dose pills are defined as those containing less than 50 micrograms of estrogen per dose.

According to the Rosenberg and colleagues, women who smoked more than 25 cigarettes a day and took low-dose birth control pills were 32 times more likely to have a heart attack than women who did not smoke or take the pills.

In an interview with Reuters Health, Rosenberg noted that the overall risk of heart attack among women under 45 is low, especially if they do not smoke. For instance, while a 25-year-old woman who smokes heavily and uses an oral contraceptive increases her risk of a heart attack, her overall risk remains low, since the underlying risk is so small, Rosenberg explained.

"However, the risk...increases with age," she said. "For an older woman, for example, one in her 40s, the increase in risk would be appreciable."

The study did not find a higher risk of heart attack among birth control pill users who did not smoke or among those who smoked fewer than 25 cigarettes a day.

The researchers conclude that the estimated increase in heart attack risk for heavy smokers who take low-dose birth control pills is similar to the risk for women who smoked and took higher dose preparations.

"Thus, the advice that women who use oral contraceptives should not smoke should remain in effect," Rosenberg said.

The results of the study are based on data from 627 women who suffered a nonfatal heart attack and nearly 3,000 women hospitalized for other reasons over a 14-year period. All women were younger than 45 when the study began.