Inconsistent evidence of associations between other cancers and body weight may be due in part to small sample sizes and misclassification of body weight in retrospective studies.
Thus, nondifferential misclassification of baseline weight should be minimal.
Third, adolescents' height and weight were reported by the parents rather than direct measures, which highly related to parents' psychological status and HRQoL and may potentially lead to a misclassification of body weight and severity.
Some misclassification of birth weight (Troy et al, 1996; Andersson et al, 2000) is unavoidable but likely nondifferential and thus, would have led to an underestimation of the true association.
The requirement for two consecutive examinations with obesity was to avoid the potential misclassification of body weight, either due to measurement error or fluctuations between the borderline of the 'overweight' category or the 'obese' category.
Taken together, this suggests possible misclassification of both birth weight and gestational age data according to self-report.
Generally, the overall misclassification of height and weight from self-reported data resulted in an underestimation of the proportion of overweight boys of approximately 5% and an underestimation of overweight girls of approximately 6%.
For example, in the first row of Fig. 1, to prevent misclassification the weight of the color based kernel should be reduced while the weights of other kernels should be increased.
As discussed previously, missing birthweight data or misclassification of self reported birth weight was unlikely to have caused the associations we observed.
