Obesity and risk of cancer in postmenopausal Korean Women

Purposes: To evaluate an association between obesity, measured by body mass index (BMI; kg/m²), and risk of cancer at individual and all sites in postmenopausal women. Methods: A cohort of 170,481 postmenopausal Korean women who were age 40 to 64 years at baseline measurement of BMI was observed prospectively from 1994 to 2003 for cancer incidence. Multivariable adjusted proportional hazard models were used for evaluating the association. Results: Women with a BMI of 30 kg/m² or higher had a 23% higher risk of cancer than women with a BMI between 21.0 and 22.9 kg/m² (hazard ratio = 1.23; 95% CI, 1.08 to 1.41). According to the increase in BMI level, significant positive trends existed in cancers of colon, breast, corpus uteri, and kidney with hazard ratios of 1.05 (95% CI, 1.02 to 1.08), 1.07 (95% CI, 1.05 to 1.10), 1.13 (95% CI, 1.07 to 1.20), and 1.08 (95% CI, 1.02 to 1.15), respectively, for the increase of BMI by 1 kg/m². When the analysis was limited to never-smokers, women with a BMI of 25 kg/m² or higher showed a significantly increased risk of cancers of the colon, breast, corpus uteri, and kidney and leukemia compared with the normal BMI (18.5 to 22.9 kg/m²) group. Conclusion: Although variations exist between the individual cancer sites, obesity was associated with an overall increased risk of cancer in postmenopausal Korean women. To reduce the risk of cancer, active strategies to prevent obesity should be implemented in postmenopausal women.