RISK-FACTORS ASSOCIATED WITH CERVICAL HUMAN PAPILLOMAVIRUS INFECTIONS- A CASE-CONTROL STUDY

As a part of the long-term prospective follow-up study conducted for w omen with genital human papillomavirus (HPV) infections in Kuopio Univ ersity Hospital, Finland, since 1981, a case-control study was designe d to assess risk factors for genital HPV infections. The cases (n = 69 1) were women who had been invited to attend the follow-up program on the basis of an abnormal cervical smear consistent with HPV-induced cy topathic changes, i.e., had a clinical HPV infection. The controls (n = 706) were a randomly selected group of women who had normal smears i n the screening. Both groups were asked to fill in an extensive questi onnaire focusing on detailed epidemiologic data on previous gynecologi c and obstetric history, sexual practices, sexual partners, and smokin g habits. In the multivariate analysis, eight variables emerged as ind ependent risk factors for prevalent HPV infection. These variables cou ld explain over 80% of the risk for infection. The risk for the infect ion varied with age, being highest in the age group 20-29 years, there after declining in the following 10-year age groups. The strongest ind ependent risk factor was the number of sexual partners during the past 2 years (adjusted odds ratio = 12.1; 95% confidence interval 4.3-33.8 for five or more vs. one or no partners). Among the independent risk factors that increased the risk were also current smoking (adjusted od ds ratio = 2.7; 95% confidence interval 1.7-4.3), warts in sexual part ner(s) (adjusted odds ratio = 3.2; 95% confidence interval 1.6-6.5), a nd increasing frequency of sexual intercourse per week. Independent ri sk factors with a protective effect included a normal result in the la st Papanicolaou smear, regular use of an intrauterine device as a cont raceptive method, and good personal hygiene. No significant associatio n between oral contraceptive use and risk for HPV infection was found. Condom use did not result in protection from the infection. The resul ts of this study support the concepts that sexual intercourse is the m ain form of transmission among adults and that sexual promiscuity is t he most important determinant for genital HPV infections.