Reproductive Episodes and Asymptomatic Gallstones in Females : Findings from A Nested Case-Control Study in Hokkaido, Japan

Abstract

To explore reproductive risk factors for asymptomatic gallstones in females, we conducted a nested case-control study. The study comprised 126 cases (women with asymptomatic gallstones) and 378 controls ( women free from gallstones and other diseases of the liver and biliary tract) among 3, 927 women aged 40 years or more in Y town, Hokkaido, Japan. Controls were randomly selected with an allocation ratio of 1 : 3 from 3, 599 cohort women, matching to cases for sex(female), age (2 years), residential area, and year of examination. Odds ratio analysis revealed the following major findings. (1) Women married for the first time at 22 years old or later are likely to be at greater risk of asymptomatic gallstones with odds ratios of 1.60 (95% confidence interval : 0.97-2.64) ; 1.68 (0.96-2.94) for postmenopausal women. (2) First full-term delivery at 23 years old or later tended to increase the risk by 1.63 (0.97-2.77) ; 1.63 (0.90-2.9) when postmenopausal. and (3) Pregnancy of 5 times or more also appeared to elevate the risk by 1.47 (0.97-2.22) ; 1.55 (0.94-2.57) when postmenopausal. Two odds ratios obtained by logistic regression analysis are significant: 1.67 (1.14-3.32) and 1.59 (1.01-2.52) for age at first marriage and total number of pregnancy, respectively. Finally, we emphasize that this is the first epidemiological investigation in Japan which explored an association between reproductive episodes and asymptomatic gallstone formation in women. J Epidemiol, 1993; 3 : 91-97.