To date there are no data available on the risk factors leading to a high risk human papillomavirus (HPV) infection in the German female population. Using a large German population-based study, we investigate the effects of a variety of both clinical and lifestyle risk factors such as smoking, age, sexual behavior, contraception, and sexually transmitted disease (STD) status on acquisition of HPV infection.
Women aged 30-60 years attending routine cervical screening were invited to participate in the study (n=10,040). Cervical specimens were collected and tested centrally by liquid based cytology (LBC), Aptima HPV test (AHPV) and Hybrid Capture 2 (HC2) using the high risk probe. Women were also invited to fill in questionnaires about their lifestyle. Questionnaire results of 9027 women are available and were analyzed using single, multiple, and step-wise logistic regression models, including possible interaction effects, to determine the relevant factors for HPV infection, the outcome variable. In addition, we also incorporated multiple imputation (using 20 imputation data-sets), assuming a missing at random (MAR) imputation scheme to complete our data when responses were not present. Missing data of risk factors ranged from 0% to 30%, all possible covariates were used for imputation models.
Among the 9027 women in the analysis, 8526 (94.4%) women have normal cytology findings, and 501 (5.5 %), have a cytological diagnosis of ASCUS or LSIL or higher. Increasing age, categorized by decades, was found to have an inverse effect on probability of a high risk HPV infection (OR: 0.652, p<0.000). Giving birth (dichotomized by previous birth or never having given birth) also decreased the risk of developing high risk HPV infection (OR: 0.58, p=0.001). While our survey data included the specific contraceptive method (including oral contraceptive (OC) use , condoms, IUD etc), we found that the only relevant contraceptive factor was whether the women used OC, with OC usage increasing likelihood of infection (OR 1.64, p<0.000). Smoking (dichotomous) also increases probability of infection (OR: 1.29, p<0.000).
We found that certain lifestyle factors, primarily related to sexual behavior and smoking, individually have a strong association with high risk HPV infections. However, a significant interaction effect between different factors was not observed. Additionally, we confirmed previous European study findings that increasing age decreases risk of high risk HPV infections.