Self-reported anthropometric information cannot vouch for the accurate assessment of obesity prevalence in populations of middle-aged and older Korean individuals.

While there are strong correlations between self-reported and directly measured anthropometric data, the discrepancy and systematic errors associated with these, particularly among middle-aged and older persons residing in South Korea, remain a contentious issue. All participants were selected from the Korean Longitudinal Study of Aging (KLoSA), a panel study conducted by the Korea Labor Institute; data from 510 participants (290 females; 56.9%) were analyzed. We considered general characteristics, including sex, age, education, marital status, employment, income, and residential region, and used self-rated health (SRH) as a generic indicator of health status. One-way ANOVA, t-test, and Scheffé's test (α=0.1) were employed to explore the difference between directly measured and self-reported values. Sensitivity and specificity values were used to assess the validity of obesity diagnoses based on self-reported body mass index (BMI: body weight in kilograms divided by the square of height in meters). The means of BMI differences were 1.3 (±1.2)kg/m(2) among men and 1.8 (±1.5)kg/m(2) among women. In men, the difference could be attributed to measured BMI and residential region; among women, age and education level influenced the discrepancy in BMI. Scheffé's test (α=0.1) for multiple comparisons of group means revealed that women over the age of 65 years, with lower than middle-school education, who lived in rural areas, and had a measured BMI of 25kg/m(2) or more, were more likely to have significant BMI discrepancies. In contrast, for men, significant predictors were living in rural areas and being obese. Although adequate correlations were seen in self-reported BMI, they indicated low sensitivity, with 46.5% and 60.1% among males and females, respectively. However, specificities were very high, at 97.8% and 98.0% for males and females, respectively. The diagnostic performance of self-reported BMI is insufficient for assessing obesity prevalence among middle-aged or older Koreans.