Validity of self-reported height and weight and derived body mass index in middle-aged and elderly individuals in Australia

Background: Body mass index (BMI) is an important measure of adiposity. While BMI derived from self-reported data generally agrees well with that derived from measured values, evidence from Australia is limited, particularly for the elderly.\ud \ud Methods: We compared self-reported with measured height and weight in a random sample of 608 individuals aged ≥45 from the 45 and Up Study, an Australian population-based cohort study. We assessed degree of agreement and correlation between measures, and calculated sensitivity and specificity to quantify BMI category misclassification.\ud \ud Results: On average, in males and females respectively, height was overestimated by 1.24cm (95% CI: 0.75–1.72) and 0.59cm (0.26–0.92); weight was underestimated by 1.68kg (–1.99– -1.36) and 1.02kg (–1.24– -0.80); and BMI based on self-reported measures was underestimated by 0.90kg/m2 (–1.09– -0.70) and 0.60 kg/m2 (–0.75– -0.45). Underestimation increased with increasing measured BMI. There were strong correlations between self-reported and measured height, weight and BMI (r=0.95, 0.99 and 0.95, respectively, p