title: Birth cohort effects among US-born adults born in the 1980s: foreshadowing future trends in US obesity prevalence.
abstract: BACKGROUND
  Obesity prevalence stabilized in the US in the first decade of the 2000s. However, obesity prevalence may resume increasing if younger generations are more sensitive to the obesogenic environment than older generations.
  
  
  METHODS
  We estimated cohort effects for obesity prevalence among young adults born in the 1980s. Using data collected from the National Health and Nutrition Examination Survey between 1971 and 2008, we calculated obesity for respondents aged between 2 and 74 years. We used the median polish approach to estimate smoothed age and period trends; residual non-linear deviations from age and period trends were regressed on cohort indicator variables to estimate birth cohort effects.
  
  
  RESULTS
  After taking into account age effects and ubiquitous secular changes, cohorts born in the 1980s had increased propensity to obesity versus those born in the late 1960s. The cohort effects were 1.18 (95% CI: 1.01, 1.07) and 1.21 (95% CI: 1.02, 1.09) for the 1979-1983 and 1984-1988 birth cohorts, respectively. The effects were especially pronounced in Black males and females but appeared absent in White males.
  
  
  CONCLUSIONS
  Our results indicate a generational divergence of obesity prevalence. Even if age-specific obesity prevalence stabilizes in those born before the 1980s, age-specific prevalence may continue to rise in the 1980s cohorts, culminating in record-high obesity prevalence as this generation enters its ages of peak obesity prevalence.
authors.affiliation: Department of Epidemiology, University of North Carolina at Chapel Hill, Gillings School of Global Public Health, Chapel Hill, NC 27510, USA. whitney_robinson@unc.edu
authors.forename: W R
authors.initials: WR
authors.lastname: Robinson
authors.forename: K M
authors.initials: KM
authors.lastname: Keyes
authors.forename: R L
authors.initials: RL
authors.lastname: Utz
authors.forename: C L
authors.initials: CL
authors.lastname: Martin
authors.forename: Y
authors.initials: Y
authors.lastname: Yang
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D015988:Cohort Effect; D004198:Disease Susceptibility; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D009765:Obesity / Q000453:epidemiology* / Q000517:prevention & control; D015995:Prevalence; D011634:Public Health / Q000706:statistics & numerical data* / Q000639:trends; D012307:Risk Factors; D014481:United States / Q000453:epidemiology