Study objective: The aim was to investigate the relationship between oral contraceptives, non-contraceptive oestrogens, and the risk of gallstone disease requiring surgery.
Design: This was a hospital based case-control study carried out between 1987 and 1990. Main outcome measures were frequency of consumption of oral contraceptives and non-contraceptive oestrogens, and the corresponding multivariate relative risk estimates and 95% confidence intervals (CI) in relation to various measures of use of the preparations.
Setting: A network including major teaching and general hospitals in the greater Milan area, northern Italy.
Subjects: Subjects were 235 women with gallstones requiring surgery and 538 controls admitted for acute diseases, other than digestive or hormonal diseases or those potentially influencing the use of female hormone preparations.
Main results: For oral contraceptives, the relative risk for ever use was 0.8 with 95% CI 0.4 to 1.5. With reference to duration of use, the multivariate relative risk was 1.0 for less than two and 0.5 for two or more years of use. The relative risk was 1.7 (95% CI 0.6 to 4.7) in women who had last used the pill less than five years before diagnosis, but declined to 0.4 (95% CI 0.2 to 1.0) in those who had stopped more than five years before. With reference to oestrogen replacement treatment, the relative risk for ever use was 1.9 (95% CI 1.0 to 3.1). The relative risk, however, was not related to duration of use, since it was 1.8 for less than two and 1.5 for two or more years of use. Relative risk was higher for women who had last used non-contraceptive oestrogens 10 or more years before diagnosis (2.4) than for shorter periods since last use (1.3).
Conclusions: On a clinical and public health scale, oral contraceptives and non-contraceptive oestrogens are unlikely to have an important influence in the aetiology of gallbladder disease.