Cigarette smoking increases a woman’s risk of developing cancer of the cervix, and the risk increases with the number of cigarettes smoked per day and with the younger the age at which smoking began, according to a new report.

Researchers with the International Collaboration of Epidemiological Studies of Cervical Cancer evaluated data from 23 studies on the effects of smoking on cervical cancer risk, involving 23,017 women who were initially free of cervical cancer.

Dr. Amy Berrington de Gonzales, of Cancer Research UK in Oxford, and colleagues report in the International Journal of Cancer that current smokers have a 60 percent greater risk of cervical cancer than women who never smoked.

The analysis found no association between smoking duration and risk of cervical cancer, but did show a correlation with age of starting smoking.

“It is not clear why this association was present,” Berrington said in an interview with Reuters Health. “One possible explanation is that duration of smoking was reported less accurately than age at starting smoking, and age at starting smoking is acting as a surrogate for duration of smoking, i.e. earlier age at starting smoking is a marker of longer duration.”

Eight of the 23 studies included data on cervical infection with human papilloma virus or HPV, which has been linked to most cases of cervical cancer. In these studies, women who tested positive for HPV had a risk of cervical cancer almost two-fold higher than HPV-negative women.

These results confirm that smoking is a risk factor for cervical cancer, Berrington noted, “as the association was present also in women who were HPV-positive, strongly suggesting that the association is not just due to confounding between sexual behavior and smoking.”

SOURCE: International Journal of Cancer, March 15, 2006.