The effect of involuntary smoking on the occurrence of chronic obstructive pulmonary disease.

One hundred and three ever-married women with newly diagnosed Chronic Obstructive Pulmonary Disease (COPD), who have never smoked, and 179 ever-married women who were visiting friends or relatives at the same hospital during the same period and have never smoked, were interviewed regarding the smoking habits of their husbands. There was statistically marginally significant difference between the COPD cases and the controls with respect to their husband's smoking habits. The association was irregular with respect to daily number of cigarettes smoked but there was a smooth dose response curve with respect to life long total number of cigarettes smoked, with women whose husband smoked more than 300 thousand cigarettes having a relative risk of 1.8 (90% confidence interval of 0.9-3.6) compared to women whose husband has never smoked. These findings, and converging related evidence, indicate that exposure to environmental tobacco smoke may be a risk factor for the development of COPD.