Smoking as a risk factor in cancer of the cervix: additional evidence from a case-control study.

The results of a case-control study in Toronto, Canada, demonstrated a two-fold risk of invasive squamous cell carcinoma of the cervix among current smokers relative to women who had never smoked. This significant effect of smoking was not diminished by simultaneously adjusting for age, education, and indices of sexual behavior. This association was further supported by the observations that ex-smokers were at a lower risk than current smokers (1.7 versus 2.3), and that the risk increased with the amount of cigarettes smoked (2.2 for less than half a pack per day to 2.9 for more than one pack per day).