Smoke-Filled Rooms.

ETS Causes Menstrual Pain

Studies show that women who smoke are twice as likely to experience dysmenorrhea (painful menstruation) as nonsmokers, and smoking prolongs the symptoms of this condition. Fewer data are available on whether secondhand exposure to environmental tobacco smoke (ETS) at home or work also raises the risk for dysmenorrhea in nonsmoking women. In this issue, a team of environmental researchers headed by epidemiologist Changzhong Chen of the Harvard School of Public Health report that ETS exposure does indeed increase the occurrence of dysmenorrhea in nonsmoking women [EHP 108:1019-1022]. Moreover, the more ETS a woman is exposed to daily, the higher her risk for dysmenorrhea.

Dysmenorrhea is a common gynecological problem that not only reduces quality of life but also accounts for significant medical costs and absenteeism from work. Previous studies that looked for an association between ETS and dysmenorrhea were not well controlled. For example, they included retrospective studies that relied on subject recall of symptoms, and involved older women (who have less dysmenorrhea) or women with prior dysmenorrhea (which may have been influenced by factors other than ETS).

The current, better-controlled study followed 165 newly wed, nonsmoking Chinese women through 625 menstrual cycles. The women's average age was 26 years, and they had no past history of dysmenorrhea. Chinese society offers a unique opportunity to study the consequences of ETS exposure because men smoke heavily, whereas women generally do not smoke. Because the women in the study were trying to conceive for the first time, none of them used birth control. This ruled out any impact of previous births or contraceptives, both of which have been implicated in contributing to dysmenorrhea.

Each woman kept a daily diary of menstrual symptoms and the number of cigarettes smoked indoors in her presence. The diaries were collected when a woman either became pregnant or a year had passed without conception.

Three-quarters of the women were exposed to ETS, largely via husbands who smoked around them. The incidence of dysmenorrhea--characterized as pain in the abdomen or lower back on two or more days of menstrual bleeding--varied with the level of ETS exposure, ranging from 9.7% in nonexposed women to as high as 16.9% in women with the highest level of exposure. Compared to women with no exposure to ETS, the researchers calculated that the risk of dysmenorrhea tripled in women with the highest ETS exposure, which corresponded to their husbands' smoking 2.6 or more cigarettes inside per day. In women receiving a middle level of exposure to ETS (0.8-2.5 cigarettes), the risk of dysmenorrhea was 2.5 times greater than in nonexposed women. The researchers estimate that for each day that two more cigarettes are smoked at home, the risk of dysmenorrhea climbs by 30%.

Refraining from smoking and limiting exposure to ETS could benefit the reproductive health of women, the researchers suggest. In future studies, they plan to evaluate whether exposure to ETS makes it more difficult for women to conceive.