title: Age, period and cohort effects on body weight and body mass index in adults: The Doetinchem Cohort Study.
abstract: OBJECTIVE
  To study the development of body weight with ageing, in a general adult population, taking into account possible period and cohort effects.
  
  
  METHODS
  A prospective cohort study with 11 years of follow-up. At baseline and after 6 and 11 years, body weight and height were measured.
  
  
  METHODS
  The Doetinchem Cohort Study, consisting of inhabitants of Doetinchem, a town in a rural area of The Netherlands.
  
  
  METHODS
  In total, 4070 healthy men and women aged 20-59 years at baseline.
  
  
  RESULTS
  Increase in BMI with ageing was less profound based on cross-sectional data than based on longitudinal data. More recent-born cohorts had a higher BMI at a given age than cohorts who were born earlier. Increase in mean BMI with ageing was observed in all age groups and was similar for groups with a different educational level. Highest increase in BMI over 11 years was observed in the youngest group, aged 20-29 years at baseline (2.2 [95 % CL 2.0, 2.3] kg/m2), and lowest increase in the oldest group, aged 50-59 years at baseline (1.1 [1.0, 1.3] kg/m2).
  
  
  CONCLUSIONS
  Findings of the present study using longitudinal data suggest that increase in BMI with ageing is underestimated in all age groups by studying cross-sectional data only. Further, weight gain is present in all educational levels and does not stop at middle age.
authors.affiliation: Division of Public Health, National Institute for Public Health and the Environment (RIVM), Antonie van Leeuwenhoeklaan 9 PO Box 1, 3720 BA Bilthoven, The Netherlands. astrid.nooyens@rivm.nl
authors.forename: Astrid C J
authors.initials: AC
authors.lastname: Nooyens
authors.forename: Tommy L S
authors.initials: TL
authors.lastname: Visscher
authors.forename: W M Monique
authors.initials: WM
authors.lastname: Verschuren
authors.forename: A Jantine
authors.initials: AJ
authors.lastname: Schuit
authors.forename: Hendriek C
authors.initials: HC
authors.lastname: Boshuizen
authors.forename: Willem
authors.initials: W
authors.lastname: van Mechelen
authors.forename: Jacob C
authors.initials: JC
authors.lastname: Seidell
mesh_terms: D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D015992:Body Mass Index; D001835:Body Weight; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004522:Educational Status; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D009765:Obesity / Q000453:epidemiology*; D011446:Prospective Studies; D015430:Weight Gain; D055815:Young Adult