Urticaria and the risk of cancer: a Danish population-based cohort study

• Published in: British journal of dermatology (1951) Vol. 191; no. 5; pp. 706 - 712
• Main Authors: Sørensen, Sissel B T, Farkas, Dóra K, Vestergaard, Christian, Schmidt, Sigrun A J, Lindahl, Lise Maria, Mansfield, Kathryn E, Langan, Sinead M, Sørensen, Henrik T
• Format: Journal Article
• Language: English
• Published: England 17.10.2024
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Child; Child, Preschool; Cohort Studies; Cross-Sectional Studies; Denmark - epidemiology; Female; Follow-Up Studies; Humans; Incidence; Infant; Male; Middle Aged; Neoplasms - epidemiology; Neoplasms - etiology; Risk Factors; Urticaria - epidemiology; Young Adult; Denmark
• ISSN: 0007-0963; 1365-2133; 1365-2133
• DOI: 10.1093/bjd/ljae264

Urticaria has been tentatively linked to cancer, but epidemiological evidence supporting this link is sparse and conflicting. We conducted a population-based cohort study using healthcare databases covering the Danish population (January 1980-December 2022). We followed 87 507 people for a median of 10.1 years after their first hospital contact for urticaria. To examine associations of a hospital diagnosis of urticaria with incident cancer. We computed the absolute risk of cancer and standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) standardized to Danish national cancer rates. In a cross-sectional analysis, we examined whether the extent of cancer spread differed between people with vs. without a previous urticaria diagnosis. The overall SIR for all types of cancer was 1.09 (95% CI 1.06-1.11) based on 7788 observed vs. 7161 expected cases. The risk for any cancer was 0.7% (95% CI 0.6-0.7) for the first year of follow-up. Cancer was diagnosed in 588 people with urticaria during the first year of follow-up (SIR 1.49, 95% CI 1.38-1.62) and in 7200 people thereafter (SIR 1.06, 95% CI 1.04-1.09). During the first year of follow-up, we found strong associations with haematological cancers (e.g. non-Hodgkin lymphoma; SIR 2.91, 95% CI 1.92-4.23). Cancer stage was similar in people with vs. without a previous urticaria diagnosis. At the time of urticaria diagnosis, or in the first year afterward, we found a large increase in the risk of cancer. In subsequent years, a persistent 6% increase in risk remained. Diagnostic efforts may partly explain the elevated short-term risk, but occult cancer may promote urticaria, or cancer and urticaria share common risk factors.