OBJECTIVE: Inflammatory bowel disease (IBD) is associated with venous thromboembolism (VTE). Whether functional gastrointestinal disorders, such as irritable bowel syndrome (IBS), are associated with VTE has not been determined. This nationwide study aimed to determine the risk of VTE in IBS outpatients in primary and specialist care.
DESIGN: We performed two matched case-control studies. Cases (n = 90,502) were individuals in Sweden aged 18-80 years with a first hospital diagnosis of VTE between 2001 and 2010. Five controls (n = 452,510) from the Swedish Total Population Register were matched to each case for birth, sex, country of birth, and education level. Diagnosis of IBS was determined in the Swedish hospital outpatient register. This procedure was replicated for the primary care population. As the Primary Care data did not have nationwide coverage, we only included individuals that were registered in the Primary Care database. A total of 9766 cases of hospital diagnosed VTE individuals could be found in the Primary Care population and they were matched to 48,830 controls also from the Primary health care population. Conditional logistic regression was used to determine odds ratio (OR) for first VTE diagnosis. Results The adjusted OR for VTE when IBS was diagnosed in hospital outpatient care was 1.49 (95% confidence interval 1.33-1.67). The crude OR for VTE was 1.18 (0.94-1.48) when IBS was diagnosed in primary care.
CONCLUSIONS: This is the first study describing an association between VTE and IBS. The results suggest that specialist treated IBS patients have increased risk of VTE.