title: Body Mass Index and Mortality in the General Population and in Subjects with Chronic Disease in Korea: A Nationwide Cohort Study (2002-2010).
abstract: BACKGROUND
  The association between body mass index (BMI) and mortality is not conclusive, especially in East Asian populations. Furthermore, the association has been neither supported by recent data, nor assessed after controlling for weight changes.
  
  
  METHODS
  We evaluated the relationship between BMI and all-cause or cause-specific mortality, using prospective cohort data by the National Health Insurance Service in Korea, which consisted of more than one million subjects. A total of 153,484 Korean adults over 30 years of age without pre-existing cardiovascular disease or cancer at baseline were followed-up until 2010 (mean follow-up period = 7.91 ± 0.59 years). Study subjects repeatedly measured body weight 3.99 times, on average.
  
  
  RESULTS
  During follow-up, 3,937 total deaths occurred; 557 deaths from cardiovascular disease, and 1,224 from cancer. In multiple-adjusted analyses, U-shaped associations were found between BMI and mortality from any cause, cardiovascular disease, and cancer after adjustment for age, sex, smoking status, alcohol consumption, physical activity, socioeconomic status, and weight change. Subjects with a BMI < 23 kg/m2 and ≥ 30 kg/m2 had higher risks of all-cause and cause-specific mortality compared with the reference group (BMI 23-24.9 kg/m2). The lowest risk of all-cause mortality was observed in subjects with a BMI of 25-26.4 kg/m2 (adjusted hazard ratio [HR] 0.86; 95% CI 0.77 to 0.97). In subgroup analyses, including the elderly and those with chronic diseases (diabetes mellitus, hypertension, and chronic kidney disease), subjects with a BMI of 25-29.9 kg/m2 (moderate obesity) had a lower risk of mortality compared with the reference. However, this association has been attenuated in younger individuals, in those with higher socioeconomic status, and those without chronic diseases.
  
  
  CONCLUSIONS
  Moderate obesity was associated more strongly with a lower risk of mortality than with normal, underweight, and overweight groups in the general population of South Korea. This obesity paradox was prominent in not only the elderly but also individuals with chronic disease.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Nam Hoon
authors.initials: NH
authors.lastname: Kim
authors.affiliation: Department of Biostatistics, Korea University College of Medicine, Seoul, Korea.
authors.forename: Juneyoung
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Statistics, Korea University, Seoul, Korea.
authors.forename: Tae Joon
authors.initials: TJ
authors.lastname: Kim
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Nan Hee
authors.initials: NH
authors.lastname: Kim
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Kyung Mook
authors.initials: KM
authors.lastname: Choi
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Sei Hyun
authors.initials: SH
authors.lastname: Baik
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Dong Seop
authors.initials: DS
authors.lastname: Choi
authors.affiliation: Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, United States of America.
authors.forename: Rodica
authors.initials: R
authors.lastname: Pop-Busui
authors.affiliation: Department of Statistics, Korea University, Seoul, Korea.
authors.forename: Yousung
authors.initials: Y
authors.lastname: Park
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Sin Gon
authors.initials: SG
authors.lastname: Kim
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002908:Chronic Disease / Q000401:mortality*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D056910:Republic of Korea