Hospital-diagnosed overweight and obesity related to cancer risk: a 40-year Danish cohort study

Background Obesity is associated with metabolic abnormalities that predispose patients to increased cancer risk. Contemporary data on the long-term risk of specific cancers are sparse among patients with hospital-diagnosed overweight and obesity. Objectives To examine the overall cancer incidence and specific site-related cancer incidences among patients with overweight and obesity, compared to the general Danish population. Methods For this 40-year (1977-2016), nationwide, Danish cohort study, we reviewed medical databases to identify individuals with hospital-based overweight and obesity diagnoses. We computed age- and gender-standardized incidence ratios (SIRs) for subsequent cancer compared to the general population. Results We observed 20 706 cancers among 313 321 patients diagnosed with overweight and obesity (median age 43 years; median follow-up 6.7 years, range 1-40 years) compared to the 18 480 cancers expected; thus, the SIR was 1.12 [95% confidence interval (95% CI): 1.11-1.14]. The SIR associated with overweight and obesity was increased with concomitant comorbidities, like type 2 diabetes (SIR: 1.18; 95% CI: 1.13-1.23) and alcoholism-related diseases (SIR: 1.62; 95% CI: 1.45-1.82). The SIR was 1.31 (95% CI: 1.28-1.34) for cancers previously identified as obesity-related, including pancreatic (SIR: 1.38; 95% CI; 1.27-1.49) and postmenopausal breast cancer (SIR: 1.14; 95% CI: 1.09-1.19). Obesity/overweight status also elevated the SIRs for haematological (SIR: 1.24; 95% CI: 1.18-1.29) and neurological cancers (SIR: 1.19; 95% CI: 1.11-1.27]. In contrast, SIRs were 1.01 (95% CI: 0.97-1.05) for immune-related cancers, 0.88 (95% CI: 0.82-0.95) for malignant melanoma, and 0.88 (95% CI: 0.85-0.92) for hormone-related cancers, other than postmenopausal breast cancer. Conclusion In this large cohort study, overweight and obesity was associated with increased risk of several common cancers.