Determinants of oral contraceptive use in northern Italy.

Socio-demographic characteristics, general lifestyle habits, reproductive and medical histories were compared of 328 women who had ever used oral contraceptives and 2306 never users from a case-control surveillance conducted in Northern Italy. Oral contraceptive use was positively and strongly related with the level of education and indicators of social class. The rate ratio of ever use (adjusted for age and diagnostic category) was 3.3 for women with 12 years of education or more compared with less than 7 years, and 3.0 for women of highest compared with lowest social class. The frequency of pill use was lower among never married women, and significantly elevated among smokers (rate ratio = 2.4 for heavy smokers). In contrast, no relation was evident between alcohol or coffee consumption and pill use. Likewise, ever users of oral contraceptives were not significantly different from women who had never used the pill with regard to major reproductive factors (parity and age at first pregnancy) or several medical variables of potential interest (e.g., diabetes, hypertension, hyperlipidemia), with the only possible exclusion of obesity which was less frequent among pill users. Thus, this study indicates that the major determinants of the persistently low frequency of oral contraceptive use in this Northern Italian population are social rather than reproductive or medical factors. These findings have important implications for epidemiological research on oral contraceptive and disease in this population, and underline the importance of selection and screening of oral contraceptive users on the basis of knowledge of medical factors and lifestyle habits.