Main Outcomes and Covariates
The endpoint of this study was defined as IBD diagnosis (ICD-9-CMcodes 555 and 556), including UC (ICD-9-CM code 556) and CD
(ICD-9-CM code 555). We divided participants into 3 age groups:
20–34 years, 35–49 years, and >50 years. Some IBD-related
medical comorbidities, including hypertension (ICD-9-CM codes
401-405), diabetes (ICD-9-CM code 250), hyperlipidemia
(ICD-9-CM code 272), cardiovascular disease (ICD-9-CMcodes 430-438), heart failure (ICD-9-CM code 428), chronic
obstructive pulmonary disease (ICD-9-CM codes 491, 492, and 496),
chronic kidney disease (ICD-9-CM codes 580-589), alcohol-related
diseases (ICD-9-CM codes 291, 303, 305.00, 305.01, 305.02,
305.03, 571.0-571.3, 790.3, and V11.3), cirrhosis (ICD-9-CM code
571), and biliary stones (ICD-9-CM code 574), were considered
potential confounding factors.