title: Underweight and mortality.
abstract: According to most prospective studies, being underweight (BMI<18·5 kg/m2) is associated with significantly higher mortality than being of normal weight, especially among smokers. We aimed to explore in a generally lean population whether being underweight is significantly associated with increased all-cause mortality.
  
  
  
  Prospective cohort study.
  
  
  
  Korea Medical Insurance Corporation study with 14 years of follow-up.
  
  
  
  After excluding deaths within the first 5 years of follow-up (1993-1997) to minimize reverse causation and excluding participants without information about smoking and health status, 94 133 men and 48 496 women aged 35-59 years in 1990 were included.
  
  
  
  We documented 5411 (5·7 %) deaths in men and 762 (1·6 %) in women. Among never smokers, hazard ratios (HR) for underweight individuals were not significantly higher than those for normal-weight individuals (BMI=18·5-22·9 kg/m2): HR=0·87 (95 % CI 0·41, 1·84, P=0·72) for underweight men and HR=1·12 (95 % CI 0·76, 1·65, P=0·58) for underweight women. Among ex-smokers, HR=0·86 (95 % CI 0·38, 1·93, P=0·72) for underweight men and HR=3·77 (95 % CI 0·42, 32·29, P=0·24) for underweight women. Among current smokers, HR=1·60 (95 % CI 1·28, 2·01, P<0·001) for underweight men and HR=2·07 (95 % CI 0·43, 9·94, P=0·36) for underweight women.
  
  
  
  The present study does not support that being underweight per se is associated with increased all-cause mortality in Korean men and women.
authors.affiliation: 1Department of Preventive Medicine,Yonsei University College of Medicine,50-1 Yonsei-ro,Seodaemun-gu,Seoul 120-752,Republic of Korea.
authors.forename: Joo Young
authors.initials: JY
authors.lastname: Lee
authors.affiliation: 1Department of Preventive Medicine,Yonsei University College of Medicine,50-1 Yonsei-ro,Seodaemun-gu,Seoul 120-752,Republic of Korea.
authors.forename: Hyeon Chang
authors.initials: HC
authors.lastname: Kim
authors.affiliation: 1Department of Preventive Medicine,Yonsei University College of Medicine,50-1 Yonsei-ro,Seodaemun-gu,Seoul 120-752,Republic of Korea.
authors.forename: Changsoo
authors.initials: C
authors.lastname: Kim
authors.affiliation: 2Cancer Policy Branch,National Cancer Center,Ilsan-ro,Ilsandong-gu,Gyeonggi-do,Republic of Korea.
authors.forename: Keeho
authors.initials: K
authors.lastname: Park
authors.affiliation: 3Department of Preventive Medicine,Yonsei University Wonju College of Medicine,Gangwon-do,Republic of Korea.
authors.forename: Song Vogue
authors.initials: SV
authors.lastname: Ahn
authors.affiliation: 4Office of Biostatistics,Ajou University School of Medicine,Suwon,Republic of Korea.
authors.forename: Dae Ryong
authors.initials: DR
authors.lastname: Kang
authors.affiliation: 5Clinical Gerontology Unit,Addenbrookes' Hospital,University of Cambridge,Cambridge,UK.
authors.forename: Kay-Tee
authors.initials: KT
authors.lastname: Khaw
authors.affiliation: 6Departments of Nutrition and Epidemiology,Harvard School of Public Health,Boston,MA,USA.
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
authors.affiliation: 1Department of Preventive Medicine,Yonsei University College of Medicine,50-1 Yonsei-ro,Seodaemun-gu,Seoul 120-752,Republic of Korea.
authors.forename: Il
authors.initials: I
authors.lastname: Suh
mesh_terms: D000328:Adult; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D056910:Republic of Korea / Q000453:epidemiology; D012907:Smoking; D013851:Thinness / Q000401:mortality*
keywords: Korea; Mortality; Obesity; Smoking; Thinness