Abstract A57: Validity of self-reported body mass index among African American breast cancer survivors: The Women's Circle of Health Follow-Up Study
Authors: Qin Bo , Llanos Adana A.M. , Szamreta Elizabeth A. , Plascak Jesse J. , Ambrosone Christine , Demissie Kitaw , Hong Chi-Chen , Bandera Elisa V. 
Published: February 2019

Background: Compared to interviewer-measured, self-reported weight and height are oftentimes less burdensome to participants and less costly in epidemiologic studies. Validity studies of body mass index (BMI) based on self-reported weight and height have shown that individuals commonly underestimate their BMI, but the accuracy varies by participants' characteristics such as weight status and race/ethnicity. However, information is lacking on the validity of self-reported BMI among African American breast cancer survivors, who are known to have a high prevalence of obesity.

Objective: The primary objective of this study was to evaluate the validity of BMI, based on self-reported weight and height, among African American breast cancer survivors. The secondary aim was to identify factors associated with BMI misreporting.

Methods: The Women's Circle of Health Follow-Up Study is an ongoing population-based longitudinal study of African American breast cancer survivors in New Jersey. Eligible participants at baseline include self-identified African American women aged 20 to 75 years, with histologically confirmed breast cancer diagnosis. Active follow-up visits are ongoing to obtain updated information including self-reported and interviewer-measured anthropometric data. To date, 243 women completed the follow-up 1 visit and their self-reported and interviewer-measured anthropometric data were available for comparison. Pearson correlation and Cohen's kappa coefficients were used to describe the relationship between self-reported and interviewer-measured BMI (at follow-up 1) as continuous and categorical, respectively. Multinomial logistic regressions were used to identify factors associated with reporting accuracy. We also evaluated the associations of self-reported and interviewer-measured BMI with obesity-related health outcomes, using hypertension as an example, to evaluate the impact of potential misreporting.

Results: The mean difference (standard deviation) between self-reported and measured BMI was -0.41 (1.49) kg/m2. Self-reported and interviewer-measured BMI values were highly correlated among all participants (r = 0.97) and when stratified by participants' characteristics (e.g., age, smoking, tumor grade; all r &gt;0.90). The agreement between BMI categories (i.e., normal weight, overweight, obese I, II, and III) based on self-reported and interviewer-measured data was good (kappa = 0.75). Women who were older, had higher-grade tumors, and had greater BMI, percent body fat, and waist-to-hip ratio were more likely to under-report their BMI by ≥3%. Women who were current smokers, had higher-grade and ER-negative tumors, and had lower BMI and percent body fat were more likely to over-report by ≥3%. The BMI-hypertension association was similar using self-reported BMI (OR per 5 kg/m2 increase: 1.63; 95% CI: 1.27-2.10) and measured BMI (OR per 5 kg/m2 increase: 1.58; 95% CI: 1.23-2.03).

Conclusion: Women who were older, current smokers, had higher-grade and ER-negative tumors, and had higher BMI, percent body fat, and waist-to-hip ratio had higher odds of misreporting their BMI. However, overall, self-reported BMI was reasonably accurate among African American breast cancer survivors in this study.

Citation Format: Bo Qin, Adana A.M. Llanos, Elizabeth A. Szamreta, Jesse J. Plascak, Christine Ambrosone, Kitaw Demissie, Chi-Chen Hong, Elisa V. Bandera. Validity of self-reported body mass index among African American breast cancer survivors: The Women's Circle of Health Follow-Up Study [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr A57.