Cigarette smoking and parity as risk factors for the development of symptomatic gall bladder disease in women: results of the Royal College of General Practitioners' oral contraception study.

The effects of cigarette smoking and parity on the development of symptomatic gall bladder disease remain controversial. These relations have been examined in a cohort of 46,000 women followed for up to 19 years during the Royal College of General Practitioners' (RCGP) oral contraception study. During follow up, 1087 women were recorded as experiencing their first ever episode of symptomatic cholelithiasis (International Classification of Diseases, 8th revision (ICD-8) 574) or cholecystitis (ICD-8 575). Smokers were more likely to develop symptomatic gall bladder disease than non-smokers (relative risk 1.19; 95% confidence intervals (95% CI) 1.06 to 1.34) and there was a significant trend with the number of cigarettes smoked daily (test for trend chi 2 = 7.58, p < 0.01). This relation was most apparent among never users of oral contraceptives, although similar trends were found among current and former users. A significant direct relation between symptomatic gall bladder disease and parity was also found (test for trend chi 2 = 21.89, p < 0.001). When all were examined together a trend of increasing risk with lower social class was also found (test for trend chi 2 = 5.72, p = 0.02). Current users of oral contraceptives had a moderately increased risk of symptomatic gall bladder disease (relative risk 1.15; 95% CI 0.99 to 1.34), unlike former users (relative risk 1.03; 95% CI 0.90 to 1.18). These results suggest that smoking and parity are important risk factors for the development of symptomatic gall bladder disease in women.