Cohort study of body mass index and risk of over 100 cancer types in 4.1 million individuals in Sweden

Obesity is an established risk factor for 13 cancers. The Obesity and Disease Development Sweden (ODDS) pooled cohort study aimed to identify further potentially obesity-related cancers. Using Cox regression models on 4,142,349 individuals in Sweden (mean age 27.1 years at weight measurement) the authors calculated HRs for the association between BMI and the risk of 122 cancers and cancer subtypes. Cancers with a positive association (HR > 1) at an α-level of 0.05 for obesity (BMI ≥ 30 kg/m²) versus normal weight (18.5-24.9) or per 5 kg/m² higher BMI were considered potentially obesity-related. After 100.2 miilion person-years of follow-up, 332,501 incident cancer cases were recorded. Fifteen cancers in men and 16 cancers in women were potentially obesity-related. These were cancers of the head and neck, gastrointestinal tract, malignant melanoma, genital organs, endocrine organs, connective tissue, and hematological malignancies. The HR per 5 kg/m² higher BMI was 1.17 (95% CI 1.15-1.20) in men and 1.13 (1.11-1.15) in women for potential obesity-related cancers. The authors conclude that these results suggest that a large number of potential obesity-related cancers could be added to the already established ones.