We assessed the association between metabolic health status and the incidence of bladder cancer using nationally representative data from the national Health insurance System and national Health Checkups (NHC) databases in South Korea. Data for 11,781,768 men who participated in the NHC between 2009 and 2012 were analysed. The normal-weight and physically obese categories were defined as body mass indexes (BMI) < 25 and ≥25 kg/m 2 , respectively. Metabolically obese was defined as the presence of ≥3 components of metabolic syndrome. The participants were stratified into metabolically healthy, normal-weight (MHNW); metabolically obese, normal-weight (MONW); metabolically healthy, obese (MHO); metabolically obese, obese (MOO). Multivariate-adjusted Cox regression analysis was conducted to examine the association between metabolic health status and the incidence of bladder cancer. The study participants included 17,777 men newly registered with bladder cancer. Analysis according to metabolic health status classification revealed a higher multivariableadjusted hazard ratio in the MOO, MONW group than in the MHO group (1.307 [95% CI: 1.258-1.358], 1.183 [95% CI: 1.137-1.231] and 1.066 [95% CI: 1.017-1.119], respectively; hazard ratios given relative to MHnW group) We found an association between metabolic health status and the incidence of bladder cancer, with an increasing risk according to the number of metabolic health status components.
Data source and study population. InSouth Korea, the National Health Insurance System (NHIS) established in 2000 covers about 98% of the citizens (about 50 million in 2014) 15 . All insurance members and dependents are asked to undergo a free biannual health check-up as part of the NHIS. In 2013, about 68% of members received a full health check-up 16 , making it possible to obtain information on population-wide disease status 17 .In the present study, sex, birth date, past history, medication history, socioeconomic data, body size phenotypes, and diagnostic codes based on the International Statistical Classification of Diseases and related health problems 10th revision, Clinical Modification (ICD-10-CM) were retrieved.Data from a total of 11,781,768 men who participated in the National Health Checkups (NHC) program between January 2009 and December 2012 were analysed. Body size phenotypes were classified according to BMI, which was calculated from measured height and weight, and the presence or absence of metabolic syndrome according to the results of the NHC 17 .Since patients that are diagnosed with cancer, cardiovascular disease, cerebrovascular disease, and rare disease are entitled to economic benefits from the Korean government 18 , almost all physician-diagnosed cancer patients are registered in the central database 19 . Bladder cancer was coded as C67 in the ICD-10-CM. A flowchart for the selection of the study participants is shown in Fig. 1.
Definition of metabolic health status. 'Physically obese' was categorized according to the World HealthOrganization's (WHO) definit...