Exposure to secondhand smoke appears to increase the risk of cervical cancer, albeit to a lesser extent than active smoking, new research shows.

“There was good reason to think that passive smoking might be associated with cervical cancer, given the link with active smoking,” Dr. Anthony J. Alberg, from Johns Hopkins University in Baltimore, told AMN Health.

He noted that studies of cross-sections of different populations have supported the link to passive smoking, but there has been a lack of evidence from forward-looking studies that follow people over a period of time to see who develops cervical cancer.

To address this issue, Alberg’s team conducted a study involving nearly 25,000 women who were surveyed about household smoking in 1963 and over 26,000 who were surveyed in 1975. Cancer registry data were analyzed to determine the occurrence of cervical cancer in the two groups up to 15 years after they were surveyed.

The researchers’ findings appear in the medical journal Obstetrics and Gynecology.

Exposure to passive smoking increased the risk of cervical cancer by 2.1-fold in the 1963 group and 1.4-fold in the 1975 group. The corresponding increases in risk for women who actively smoked were 2.6- and 1.7-fold.

“The twofold increased risk linked to passive smoking in the earlier cohort is almost too strong,” Alberg said. “I suspect the true risk lies somewhere between the risks seen in each cohort, probably closer to the 1.4-fold increased risk. Unfortunately, we don’t have a good explanation for why the risks differed so much between the cohorts.”

Nonetheless, he added, there is really “no reason why passive smoking shouldn’t be associated with cervical cancer if active smoking is.”

SOURCE: Obstetrics and Gynecology, January 2005.