Accuracy of self-reported weight, height and body mass index among older people in Japan

Aim: Weight and height are usually self-reported in population-based epidemiological surveys. While the accuracy of self-reports has been extensively studied in younger populations, less is known in older populations. We investigated the accuracy of self-reported weight, height and body mass (BMI) in an older cohort in Japan, where overweight/obesity and underweight coexist.

Methods: We used data from older Japanese adults (≥65 years) participating in the Japan Gerontological Evaluation Study in 2016 to 2017 (7357 men and 9271 women). Self-report data were linked to objective data obtained from clinical examinations.

Results: The mean ± standard deviation (SD) age was 74.5 ± 5.8 years, mean ± SD weight, height and BMI were 55.7 ± 10.1 kg, 156.0 ± 8.9 cm and 22.8 ± 3.1, respectively. Results showed high intraclass correlation coefficients for self-reported and measured values (0.97 for weight; 0.96 for height). While weight/height were overestimated among men (weight by 0.096 kg; height by 0.27 cm) and women (weight by 0.18 kg; height by 0.27 cm), BMI tended to be slightly underestimated (-0.034 kg/m² for men; -0.037 kg/m² for women). However, the absolute differences between self-reported and measured values were not negligible; people had a higher risk for both under- and overestimation of their BMI category with increasing age. Lower education predicted BMI overestimation, whereas lower income predicted BMI underestimation.

Conclusions: Overall accuracy of self-reported body habitus was higher in this cohort of older Japanese compared with previous reports. Nevertheless, misclassification of BMI due to the misreporting of their weight/height was more common among the oldest-old, as well as those with lower education and income. Geriatr Gerontol Int 2020; 20: 803-810.