Risk of symptomatic gallstones in women with severe obesity

Although obesity is a well-recognized risk factor for gallstones, the excess risks associated with higher levels of obesity and recent weight change are poorly quantified. We evaluated these issues in the Nurses' Health Study. Among 90 302 women aged 34-59 y at baseline followed from 1980 to 1988, 2122 cases of newly diagnosed symptomatic gallstones occurred during 607 104 person-years of follow-up. From 1980 to 1986, 488 cases of newly diagnosed unremoved gallstones were documented. We observed a striking monotonic increase in gallstone disease risk with obesity; women with a body mass index (BMI) > 45 kg/m² had a sevenfold excess risk compared with those whose BMI was < 24 kg/m². Women with a BMI > 30 kg/m² had a yearly gallstone incidence of > 1% and those with a BMI ≥ 45 kg/m² had a rate of ≈2%/y. Recent weight loss was associated with a modestly increased risk after adjustment for BMI before weight loss. Current smoking was an independent risk factor; women smoking ≥ 35 cigarettes/d had a relative risk of 1.5 (95% CI 1.2-1.9).