The impact of obesity and overweight on medical expenditures and disease incidence in Korea from 2002 to 2013

Objectives Few studies have assessed the long-term medical costs and incidence of obesity and overweight in Asia. We evaluated the impact of body mass index (BMI) on medical expenditures and disease incidence and prevalence over more than 10 years in South Korea. Methods Using 2002-2013 data from the Korean National Claims Database, we analysed two population sets (initial BMI in 2002-2003; consistent BMI in 2002-2003 and 2012-2013). Obesity was defined by Asian BMI criteria. Incremental medical expenditures or Charlson Comorbidity Index (CCI) ratios for obese compared to normal weight individuals were calculated. Medical expenditure over 11 years was estimated by BMI using a generalised linear model. Individual obesity-related disease incidence was determined and adjusted hazard ratios were calculated. Results Data for 496,469 and 214,477 individuals were included in the entire and consistent BMI level populations, respectively. Average CCI score change in normal weight and the obesity III (BMI 35-59.99 kg/m(2)) group over 11 years were 0.94 and 1.56, respectively in the entire population, and incremental ratio in the obesity III group was 66.0% compared to the normal weight group. In consistent BMI level population, incremental ratio (92.1%) for obesity III was higher than entire population. Medical costs in the obesity III groups versus the normal weight group in the entire and consistent BMI level populations increased by 38.4% and 77.1%, respectively. Over 11 years, individuals with BMI >= 30 kg/m(2) in the entire and consistent BMI level populations had post-adjustment medical expenditures of 1.13-1.20 and 1.21-1.40 times the normal weight group, respectively. Incidence rate and adjusted hazard ratio of obesity-related disease increased in the obesity groups compared to the normal weight group. Conclusions Our findings emphasize the importance of the effective and sustainable obesity management strategies, considering the dramatic increase in obesity (BMI >= 30 kg/m(2)) in South Korea.