Determinants of hysterectomy and oophorectomy in northern Italy.

We analysed determinants of hysterectomy and oophorectomy using data from hospital control subjects, interviewed in a large case-control study on risk factors for breast cancer, conducted since 1983 in the Greater Milan area, Italy. Out of the 2916 women interviewed 355 (12.2%) were hysterectomized. Mean age at hysterectomy was 52. The cumulative probability of hysterectomy was similar in women born during the periods from 1900 to 1909 and 1910 to 1919. It rose steadily in each subsequent cohort for all ages till the cohort born between 1930 and 1939, then decreased in the cohort born between 1940 and 1949. The cumulative probability of hysterectomy by 60 years of age was 12.8% in women born between 1900 and 1909, and of 9.8%, 16.7% and 22.0% respectively in subsequent cohorts. Concerning determinants of hysterectomy, we found no relation with education and parity. Among the 355 hysterectomized women, 178 (50.1%) underwent unilateral (40 women) or bilateral (138 women) oophorectomy. The probability of oophorectomy was higher in more educated women. Compared with women who had had hysterectomy before the age of 45, those aged between 45 and 54 reported more frequently oophorectomy (odds ratio (OR): 1.5, 95% confidence interval (CI) from 0.9 to 2.3), but the OR was only 0.8 in those aged 55 or more (95% CI from 0.3 to 2.2). We found no relation between menopausal status or cohort of birth and oophorectomy.