Background: It remains unclear whether constipation is associated with cancer. We evaluated the risk of malignancies in patients with constipation requiring hospitalization. Methods: Using Danish medical registries, we calculated cumulative incidences and standardized incidence ratios (SIRs) for cancer. SIRs were computed as the observed number of gastrointestinal (GI) cancers and selected non-GI cancers in patients with constipation compared with the expected number based on national incidence rates by sex, age, and calendar year (1978-2013). Results: We identified 1,75,901 patients with constipation (59% females, median age 54 years). The cumulative incidences of GI cancers and non-GI cancers after 15 years of follow-up were 2.5% and 2.6%, respectively. During the first year of follow-up, the SIR for any GI cancer was 5.0 (95% confidence interval (CI): 4.8-5.3), driven by colon and pancreas cancers and higher for younger age groups. Beyond 1 year of follow-up, the risk declined to near unity for colorectal cancer. The risk of other GI cancers (including cancers of the esophagus, stomach, small intestine, liver, and pancreas) remained moderately increased (overall SIR =1.3, 95% CI: 1.2-1.4). Except for ovarian cancer (SIR =7.3, 95% CI: 6.3-8.4), the risk of non-GI cancers was only slightly increased during the first year of follow-up and declined to unity thereafter. Conclusions: Patients with constipation had increased short-term risk of a diagnosis of GI cancer. Beyond 1 year of follow-up, a moderately elevated risk persisted only for GI cancers other than colorectal cancer. The risk of non-GI cancers was elevated only during the first year of follow-up, particularly for ovarian cancer.
Keywords: cancer; cohort study; constipation.