Correlates of oral contraceptive use in Italian women, 1991-93

In order to understand the determinants of oral contraceptive (OC) use in Italy, we analyzed data on 1577 women aged under age 60 (median age 50 years) admitted as controls in a case-control study of breast cancer. Included in this group were women with acute, non-neoplastic, non-gynecologic, non-hormone-related diseases, admitted between 1991 and 1994 to a network of hospitals in six Italian centres. A total of 275 (17.4%) women reported ever OC use. Oral contraceptive use was strongly related to the level of education: in comparison with women reporting < 7 years of schooling, the multivariate odds ratios (OR) of ever OC use were 2.2 and 3.5, respectively, in women reporting 7-11 and > or = 12 years of schooling (chi 1(2) trend 40.87 p < 0.001). OC use was inversely related to body mass index (BMI): in comparison with leaner women (BMI, Kg/m2, < 25), the OR of being an ever OC user was 0.8 and 0.7, respectively, in women with BMI 25-< 30 and > or = 30 (chi 1(2) trend 3.36, p = 0.07). Parous women more frequently tended to be OC users than nulliparous ones, the estimated OR being 2.4 and 2.3, respectively, in women reporting 1 or 2 and 3 or more births in comparison with nulliparae. Likewise, women with history of induced abortions were more frequently ever OC users (OR for > or = 1 induced abortions vs no induced abortion, 1.8, 95% Cl 1.2-2.6). However, no relationship emerged between OC use and history of spontaneous abortions. Finally, there was no relation between pill use and history of hypertension, cholelithiasis, thyroid diseases, hyperlipidemia, family history of breast cancer, uterine fibroids and benign breast disease. Women with a history of diabetes were less likely to be OC users (OR 0.6), but the finding was not significant. The results of this analysis are comparable with those of a study conducted in the same population in the early 1980's, and suggest that sociodemographic and reproductive factors, rather than medical history, are major determinants of OC use in this population.