Smoking and human papillomavirus infection: pooled analysis of the International Agency for Research on Cancer HPV Prevalence Surveys.

BACKGROUND Smoking increases the risk of squamous-cell carcinoma of the cervix, but it is not clear whether smoking increases the risk of acquisition or persistence of human papillomavirus (HPV) infection. METHODS Information on smoking was collected from 10 areas in four continents among population-based, age-stratified random samples of women aged 15 years or older. HPV testing was performed using PCR-based enzyme immunoassay. Unconditional logistic regression was used to estimate odds ratios (OR) and corresponding 95% confidence intervals (CI) of being HPV-positive by smoking habits, adjusted for age and lifetime number of sexual partners. RESULTS Ten thousand five hundred and seventy-seven women (mean age 41.4 years) were included. Among current smokers, the risk of being HPV-positive increased with smoking intensity, after allowing for lifetime number of sexual partners: ORs for <5, 5-14 and >/=15 cigarettes per day were 1.21 (95% CI 0.95-1.54), 1.39 (95% CI 1.04-1.87) and 2.01 (95% CI 1.32-3.08), respectively, as compared with never-smokers. The risk among former smokers (OR = 0.95, 95% CI 0.73-1.23) was similar to that among never-smokers. Analyses stratified by lifetime number of sexual partners showed a significant trend in risk only for women with one lifetime sexual partner. CONCLUSIONS Our study suggests that current, though not former, smoking is associated with an increased prevalence of HPV, after allowance for sexual covariates. Among current smokers, HPV prevalence increased with smoking intensity, but a clear dose-response relationship was exclusively seen among women who declared one lifetime sexual partner.