The role of sexual factors in the aetiology of cervical dysplasia.

The effect of sexual behavior on the risk for cervical dysplasia was evaluated in a case-control study. Cases (n = 257) had a histologically confirmed diagnosis of cervical dysplasia. Controls (n = 705) were sampled from the general population. A postal questionnaire was used to obtain information about, among other things, age at first sexual intercourse, number of sexual partners, current frequency of intercourse and contraceptive use. Information was also collected about other risk factors for cervical dysplasia, in order to adjust for possible confounding. We observed higher risks for cervical dysplasia (mild, moderate and severe) with increasing number of sexual partners. This effect appeared to be dependent on smoking behaviour. For women who reported more than six sexual partners, the adjusted odds ratio (aOR) was 9.1 (95% CI: 3.5-23.7) for non-smokers, and 26.4 (95% CI: 11.8-58.8) for women who smoked > or = 20 cigarettes per day. The effects of age at first sexual intercourse and current frequency of intercourse disappeared after adjustment for other risk factors. Use of oral contraceptives for > 10 years increased the risk (aOR = 2.3; 95% CI: 1.2-4.6). Thus, the number of sexual partners, especially in combination with smoking behaviour, appeared to be the most important risk factor for cervical dysplasia.