Smoking out a source of painful menses.

Roughly half of menstruating women regularly experience cramps. The pain, which can be debilitating, accounts for some 600 million hours of lost work time annually in the United States alone. A study now finds that exposure to second-hand smoke may trigger this common gynecologic disorder.

Changzhong Chen of the Harvard School of Public Health in Boston and his colleagues studied 165 nonsmoking women in China. Each was newly married and had no history of painful menstrual periods. Every day for 1 year, or until she became pregnant, each woman recorded how many cigarettes were smoked in her home. The scientists sorted the women into four exposure groups and then summed the menstrual cycles during which women experienced pain. In the November ENVIRONMENTAL HEALTH PERSPECTIVES, the researchers report a significant link between this pain and secondhand smoke.

About 10 percent of the menses among unexposed women were painful. By contrast, the incidence of cramps in women living with smokers climbed in proportion to the number of cigarettes that were smoked daily in the home. In the highest exposure group, 16.9 percent of the menses were marked by cramps. The researchers suggest that nicotine in the smoke might cause pain by constricting blood vessels in the uterus.

The new link "contributes to mounting evidence that passive smoking is associated with adverse reproductive outcomes" and is consistent with studies finding that smokers are more likely than nonsmokers to suffer from menstrual cramps, Chen notes.