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. 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. RESULTS: On average, in males and females respectively, height was overestimated by 1.24 cm (95% CI: 0.75-1.72) and 0.59 cm (0.26-0.92); weight was underestimated by 1.68 kg (-1.99- -1.36) and 1.02 kg (-1.24- -0.80); and BMI based on self-reported measures was underestimated by 0.90 kg/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<0.001). While there was excellent agreement between BMI categories from self-reported and measured data (kappa=0.80), obesity prevalence was underestimated. Findings did not differ substantially between middle-aged and elderly participants. CONCLUSIONS: Self-reported data on height and weight quantify body size appropriately in middle-aged and elderly individuals for relative measures, such as quantiles of BMI. However, caution is necessary when reporting on absolute BMI and standard BMI categories, based on self-reported data, particularly since use of such data is likely to result in underestimation of the prevalence of obesity.
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. 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. RESULTS: On average, in males and females respectively, height was overestimated by 1.24 cm (95% CI: 0.75-1.72) and 0.59 cm (0.26-0.92); weight was underestimated by 1.68 kg (-1.99- -1.36) and 1.02 kg (-1.24- -0.80); and BMI based on self-reported measures was underestimated by 0.90 kg/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<0.001). While there was excellent agreement between BMI categories from self-reported and measured data (kappa=0.80), obesity prevalence was underestimated. Findings did not differ substantially between middle-aged and elderly participants. CONCLUSIONS: Self-reported data on height and weight quantify body size appropriately in middle-aged and elderly individuals for relative measures, such as quantiles of BMI. However, caution is necessary when reporting on absolute BMI and standard BMI categories, based on self-reported data, particularly since use of such data is likely to result in underestimation of the prevalence of obesity.
Authors: Blythe J O'Hara; Philayrath Phongsavan; Elizabeth G Eakin; Elizabeth Develin; Joanne Smith; Mark Greenaway; Adrian E Bauman Journal: BMC Public Health Date: 2013-02-26 Impact factor: 3.295
Authors: Mark F Harris; Fakhrul Md Islam; Bin Jalaludin; Jack Chen; Adrian E Bauman; Elizabeth J Comino Journal: BMC Fam Pract Date: 2013-06-16 Impact factor: 2.497
Authors: Nicholas Glozier; Helen Christensen; Sharon Naismith; Nicole Cockayne; Liesje Donkin; Bruce Neal; Andrew Mackinnon; Ian Hickie Journal: PLoS One Date: 2013-03-26 Impact factor: 3.240
Authors: Emily Banks; Grace Joshy; Walter P Abhayaratna; Leonard Kritharides; Peter S Macdonald; Rosemary J Korda; John P Chalmers Journal: PLoS Med Date: 2013-01-29 Impact factor: 11.069