ABSTRACT
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.