Purpose: Self-reported weight, height, and body mass index (BMI) are commonly used in cancer epidemiology studies, but information on the validity of self-reports among cancer survivors is lacking. This study aimed to evaluate the validity of these self-reported measures among African American (AA) breast cancer survivors, known to have high obesity prevalence.
Methods: We compared the self-reported and measured values among 243 participants from the Women's Circle of Health Follow-Up Study (WCHFS), a population-based longitudinal study of AA breast cancer survivors. Multivariable-adjusted linear regressions were used to identify factors associated with reporting errors. We also examined the associations of self-reported and measured BMI with obesity-related health outcomes using multivariable logistic regressions, with hypertension as an example, to evaluate the impact of misreporting.
Results: We found that self-reported and measured values were highly correlated among all and when stratified by participants' characteristics (intraclass correlation coefficients ≥ 0.99, 0.84, and 0.96 for weight, height, and BMI, respectively). The agreement between BMI categories (normal, overweight and obese) based on self-reported and measured data was excellent (kappa = 0.81). Women who were older, never smoked, had higher grade tumors, or had greater BMI tended to have overestimated BMI calculated from self-reported weight and height. The BMI-hypertension association was similar using self-reported (OR per 5 kg/m2 increase 1.63; 95% CI 1.27-2.10) and measured BMI (1.58; 95% CI 1.23-2.03).
Conclusions: Self-reported weight, height, and BMI were reasonably accurate in the WCHFS.
Implications for cancer survivors: Our study supports the use of these self-reported values among cancer survivors when direct measurements are not possible.
Keywords: African American; Body mass index; Cancer survivors; Self-report.