title: Feasibility and validity of a statistical adjustment to reduce self-report bias of height and weight in wave 1 of the Add Health study.
abstract: BACKGROUND
  Bias in adolescent self-reported height and weight is well documented. Given the importance and widespread use of the National Longitudinal Study of Adolescent to Adult Health (Add Health) data for obesity research, we developed and tested the feasibility and validity of an empirically derived statistical correction for self-report bias in wave 1 (W1) of Add Health, a large panel study in the United States.
  
  
  METHODS
  Participants in grades 7-12 with complete height and weight data at W1 were included (n = 20,175). We used measured and self-reported (SR) height and weight and relevant biopsychosocial factors from wave 2 (W2) of Add Health (n = 14,190) to identify sources of bias and derive the most efficient sex-specific estimates of corrected height and weight. Measured, SR, and corrected W2 BMI values were calculated and compared, including sensitivity and specificity. Final correction equations were applied to W1.
  
  
  RESULTS
  After correction, weight status misclassification rates among those who underestimated their weight status were reduced from 6.6 to 5.7 % for males and from 8.0 to 5.6 % for females compared to self-report; and the correlation between SR and measured BMI in W2 increased slightly from 0.92 to 0.93. Among females, correction procedures resulted in a 3.4 % increase in sensitivity to detect overweight/obesity (BMI ≥ 25) and 5.9 % increase in sensitivity for obesity (BMI ≥ 30).
  
  
  CONCLUSIONS
  Findings suggest that application of the proposed statistical corrections can reduce bias of self-report height and weight in W1 of the Add Health data and may be useful in some analyses. In particular, the corrected BMI values improve sensitivity --the ability to detect a true positive-for overweight/obesity among females, which addresses a major concern about self-report bias in obesity research. However, the correction does not improve sensitivity to identify underweight or healthy weight adolescents and so should be applied selectively based on research questions.
authors.affiliation: School of Social Work, University of Illinois at Urbana-Champaign, 1010 W. Nevada, MC-082, Urbana, IL, 61801, USA. jliechty@illinois.edu.|College of Medicine, University of Illinois, 506 S. Mathews, Urbana, IL, 61801, USA. jliechty@illinois.edu.
authors.forename: Janet M
authors.initials: JM
authors.lastname: Liechty
authors.affiliation: Department of Statistics, University of Illinois at Urbana-Champaign, 725 S. Wright, Champaign, IL, 61820, USA.|Illinois Statistical Office, University of Illinois at Urbana-Champaign, 725 S. Wright, Champaign, IL, 61820, USA.
authors.forename: Xuan
authors.initials: X
authors.lastname: Bi
authors.affiliation: Department of Statistics, University of Illinois at Urbana-Champaign, 725 S. Wright, Champaign, IL, 61820, USA.|Illinois Statistical Office, University of Illinois at Urbana-Champaign, 725 S. Wright, Champaign, IL, 61820, USA.
authors.forename: Annie
authors.initials: A
authors.lastname: Qu
keywords: Add Health; Body mass index; Epidemiology; Obesity; Overweight; Self-report bias; Self-report vs. measured; Self-reported weight; Statistical adjustment; Statistical correction