Validity of self-reported height and weight in women of reproductive age

Height and weight are key variables in epidemiologic research, including studies of reproductive outcomes. Optimally, this information is collected by trained study personnel. However, direct measurements are not always feasible. The purpose of this study was to investigate the accuracy of self-reported height and weight, as well as the resultant body mass index (BMI) calculated from self-reported height and weight (referred to as self-reported BMI), among a group of women of reproductive age according to select demographic variables.

A total of 381 women provided self-reported height, weight, and demographic information on a questionnaire for a study of contraceptive trends while attending a Family Medicine clinic. Height and weight were also abstracted from medical records for 275 of these study participants. Self-reported and measured values for height, weight, and BMI were compared using paired t-tests. Analysis of variance, chi-square tests, and Fisher's Exact tests were used to examine how differences between self-reported and measured values varied by select demographic factors.

Women underestimated weight by 4.6 pounds, overestimated height by 0.1 inches, and underestimated BMI by 0.8 kg/m(2). All women, regardless of age, education, race/ethnicity, or marital status, underestimated their weight. These differences were statistically significant for all groups (p<0.01) with the exception of women with a high school education. Self-reported height and weight measures classified 84% of women into appropriate BMI categories.

Overall, self-reported height and weight were found to give an accurate representation of true BMI in this study. There were some demographic differences in the ability to accurately report height and weight, particularly with respect to race/ethnicity. Future studies should investigate these racial/ethnic differences among a larger population.