title: The effect of age on the shape of the BMI-mortality relation and BMI associated with minimum all-cause mortality in a large Austrian cohort.
abstract: BACKGROUND
  It is unclear if the body mass index (BMI) associated with minimum all-cause mortality is constant throughout adult life or increasing with age.
  
  
  METHODS
  We applied multivariable fractional polynomials to the data of the Vorarlberg Health Monitoring and Prevention Program to quantify the BMI associated with minimum mortality over age. The analysis included data of 129,904 never-smoking women and men (mean age: 45.4 years) who were followed for a median of 18.6 years.
  
  
  RESULTS
  Optimum BMI in women increased with age, lying within the normal BMI category (according to the World Health Organization definition) from the age of 20 years (23.3 kg m(-2), 95% confidence interval (CI): 22.2-24.3) to the age of 54 years and in the lower half of the overweight category from the age of 55 years onwards, reaching 26.2 kg m(-2) (95% CI: 25.1-27.3) at the age of 69 years. In men, optimum BMI increased slightly from 23.7 kg m(-2) (95% CI: 22.1-25.2) at the age of 20 years until the age of 59 years, reaching a BMI of 25.4 kg m(-2) (95% CI: 24.8-26.0) and decreased afterwards to 22.7 kg m(-2) (95% CI: 20.9-24.6) at the age of 80 years.
  
  
  CONCLUSIONS
  Our results indicate that BMI associated with minimum all-cause mortality changes with age and that patterns differ by sex. Sex- and age-independent BMI recommendations might therefore be inappropriate. Further studies using flexible methods instead of predefined categories are necessary to revise BMI recommendations.
authors.affiliation: 1] Agency for Preventive and Social Medicine, Bregenz, Austria [2] Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany.
authors.forename: R S
authors.initials: RS
authors.lastname: Peter
authors.affiliation: Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Mayer
authors.affiliation: Agency for Preventive and Social Medicine, Bregenz, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Concin
authors.affiliation: 1] Agency for Preventive and Social Medicine, Bregenz, Austria [2] Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Nagel
mesh_terms: D001317:Austria / Q000453:epidemiology; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000401:mortality* / Q000517:prevention & control; D002423:Cause of Death; D015331:Cohort Studies; D015340:Epidemiologic Research Design; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008136:Longevity; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009369:Neoplasms / Q000401:mortality* / Q000517:prevention & control; D009765:Obesity / Q000401:mortality* / Q000517:prevention & control; D016016:Proportional Hazards Models; D012307:Risk Factors; D015430:Weight Gain