Associations between metabolic disorders and risk of cancer in Danish men and women - a nationwide cohort study

Background: The prevalence of metabolic disorders is increasing and has been suggested to increase cancer risk, but the relation between metabolic disorders and risk of cancer is unclear, especially in young adults. We investigated the associations between diabetes, hypertension, and hypercholesterolemia on risk of all-site as well as site-specific cancers. Methods: We consecutively included men and women from nationwide Danish registries 1996-2011, if age 20-89 and without cancer prior to date of entry. We followed them throughout 2012. Metabolic disorders were defined using discharge diagnosis codes and claimed prescriptions. We used time-dependent sex-stratified Poisson regression models adjusted for age and calendar year to assess associations between metabolic disorders, and risk of all-site and site-specific cancer (no metabolic disorders as reference). Results: Over a mean follow-up of 12.6 (+/- 5.7 standard deviations [SD]) years, 4,826,142 individuals (50.2 % women) with a mean age of 41.4 (+/- 18.9 SD) years had 423,942 incident cancers. Incidence rate ratios (IRRs) of all-site cancer in patients with diabetes or hypertension were highest immediately following diagnosis of metabolic disorder. In women, cancer risk associated with diabetes continued to decline albeit remained significant (IRRs of 1.18-1.22 in years 1-8 following diagnosis). For diabetes in men, and hypertension, IRRs stabilized and remained significantly increased after about one year with IRRs of 1.10-1.13 in men for diabetes, and 1.07-1.14 for hypertension in both sexes. Conversely, no association was observed between hypercholesterolemia (treatment with statins) and cancer risk. The association between hypertension and cancer risk was strongest in young adults aged 20-34 and decreased with advancing age. Conclusions: Diabetes and hypertension were associated with increased risk of all-site cancer.