Background: An adequate nutritional status is essential for maintaining the independence in the elderly. The height and weight self-report is considered a useful alternative for the estimation of body mass index (BMI). The validity of the self-report is an issue that has not been dealt with in developing countries.
Aim: To assess the validity of the height and weight self-report in adults Mexican citizens.
Design: Transversal study.
Study population: 1707 persons (836 males, 871 females) were asked for their height and weight and were measured.
Results: Mean (+/- standard deviation) age was 59.09 +/- 9.86 SD; mean years of education was 5.51 +/-4.67 years. We found a high correlation between self-reported and measured weight (R2= 0.837); the difference between both values rose along with the age (from 0.4 kg to 1.74 kg). A systematic difference between self-reported and measured height was found. Self-reported height was over-estimated, and the bias increased along with the age of the subjects (from 1.57 cm to 2.57 cm); further, over-estimation was larger in female individuals (+2.22 cm in female vs. +1.21 cm in male subjects). We calculated a linear model that predicts real height from self-reported height with moderate, although statistically significant results (R2= 0.39 y 0.50, for female and male, respectively, p < 0.0001). Knee height was also used to estimate "adulthood height" and thus, BMI. This method showed age-related dissimilarities, and the linear regression model yielded an unacceptably low correlation (R2= <0.10). The best method to estimate real BMI was to consider self-reported parameters.
Discussion: Height and weight estimation using self-reported parameters is an acceptable method. Its precision is not so high in subjects > 75 years. Height over-estimation is an expected finding congruent with age-related corporal changes. The estimation of height using knee height is not a useful method.
Conclusion: Height and weight self-report is a valid method that may be used to accurately estimate height and weight in Mexican people.