[32] Because gallstone disease is a hard

clinical endpoint with well-defined diagnostic critera, the risk of misclassification is likely minor, and individuals receiving ICD codes for gallstones in hospitals likely had symptomatic gallstones. In support of this, approximately 68% of individuals with symptomatic gallstone disease in our cohort underwent cholecystectomy.[11] However, we cannot rule out that a small fraction of symptomatic gallstones defined this way were, in fact, asymptomatic gallstones diagnosed incidentally. Another potential limitation to our definition of symptomatic gallstone disease is that treating physicians might be more suspicious of gallbladder disease in obese than in lean individuals. Such an ascertainment bias might have led to a slight Selleckchem PLX4032 overestimation of the BMI-gallstone association in the present study. However, the estimates of the BMI-gallstone association reported here are in agreement with those from previous studies that used ultrasound to diagnose gallstones in asymptomatic individuals (i.e., studies unlikely to suffer from ascertainment bias).[1, 2] Also, we did not have data on stone composition (i.e., cholesterol/mixed/pigment).

Thus, the pathophysiological mechanisms by which obesity influences gallstone formation could not be assessed here. Finally, we only studied white individuals of Danish descent. Because ethnic differences in gallstone prevalence are well known, the results reported here may not necessarily translate to other else ethnicities. There are also potential limitations to the use of the Mendelian randomization approach.[8] For this website example, the genetic variants used may have influenced risk of symptomatic gallstone disease by other pathways than BMI (i.e., pleiotropy). However, this concern is lessened by the use of multiple genetic variants, each associated with increased BMI and each influencing BMI independently and by different pathways.[8, 10] Also, the effect of lifelong genetically elevated BMI may have been buffered by compensatory biological mechanisms (i.e., canalisation). Canalization might theoretically obscure effects of BMI-associated genetic variants

on symptomatic gallstone disease and would thus tend to drive associations toward the null, but is unlikely to account for positive associations, as those reported in the present study. In conclusion, elevated BMI as measured at baseline, as well as genetically (lifelong and unconfounded) elevated BMI, is associated with increased risk of symptomatic gallstone disease. Taken together, this indicates that elevated BMI per se is likely a causal risk factor for symptomatic gallstone disease, which is most pronounced in women. These data reemphasize obesity as a major cause of human morbidity and provide additional impetus for lifestyle interventions aimed at weight loss among overweight and obese individuals in the general population.