Chronic diseases requiring hospitalization and risk of non-melanoma skin cancers - A population based study from Denmark

We examined the associations between chronic diseases requiring hospitalization and the risk of non-melanoma skin cancers (NMSCs) in a population-based case-control study of 4,187 patients diagnosed with a first primary NMSC in 1995 in Denmark. From the National Patient Registry covering all Danish hospitals, we obtained data on hospitalizations with chronic diseases, recorded before the date of NMSC diagnosis. Using incidence density sampling, we selected 10 age-, gender-, and residence-matched controls from the Danish Civil Registration System. We used conditional logistic regression to compute incidence rate ratios (IRRs) and 95% confidence intervals (CIs). Although no overall association was found between basal cell carcinoma (BCC) and hospitalization for chronic diseases, an elevated IRR for BCC was found among patients with connective tissue disease (IRR 1.34 (95% CI: 0.99-1.82)), transplants (IRR 8.00 (95% CI: 2.15-30)), and lymphoma (IRR 2.50 (95% CI: 1.29-4.84)). An overall association between squamous cell carcinoma (SCC) and hospitalization for chronic diseases was found and specific among patients with leukemia (IRR 7.75 (95% CI: 2.35-26)), lymphoma (IRR 3.86 (95% CI: 0.99-15)), and skin diseases (IRR 5.28 (95% CI: 1.95-14)). Our study supports the presence of an association between certain chronic diseases and NMSC, and further suggests that these results unlikely are due to bias.