Obesity, abdominal obesity and subsequent risk of kidney cancer: a cohort study of 23.3 million East Asians

BACKGROUND: Limited evidence exists regarding associations between obesity and kidney cancer among Asians. We examined the associations between obesity measures and risk of kidney cancer. METHODS: We included 23,313,046 adults who underwent health examinations provided by the Korean National Health Insurance Service 2009–2012 and performed multivariable Cox proportional hazards regression analyses. RESULTS: During 5.4 years of follow-up, 18,036 cases of kidney cancer were recorded, and cumulative incidence was 0.12%. General and abdominal obesity were associated with 1.32-fold increased risk of kidney cancer compared with groups without either obesity status. Underweight individuals showed decreased adjusted hazard ratio (HR) for kidney cancer (0.76, 95% confidence interval: 0.68–0.85) compared to those with normal body mass index (BMI), while the HRs increased among individuals with BMI 23–24.9 kg/m(2) (1.23, 1.18–1.28), 25–29.9 kg/m(2) (1.41, 1.36–1.46) and ≥30 kg/m(2) (1.77, 1.65–1.90) (P for trend < 0.001). HRs of kidney cancer increased with increasing waist circumference (WC) (P for trend < 0.001). Compared to non-obese condition, the coexistence of general and abdominal obesity increased the HR (1.45, 1.40–1.50). CONCLUSIONS: This study demonstrated positive associations of BMI and WC with kidney cancer risk. General and abdominal obesity may be risk factors of kidney cancer.