The calibration of the deviations in body mass index (BMI) due to the shrinkage of body height in elderly people: An anthropometric study

The shrinkage of body height (or stature) in the old ages brings along the problem of reliably calculating the Body Mass Index (BMI), which is an important indicator of health and nutritional status. Incorrectly calculated BMI values make it difficult to detect and follow up malnutrition, which are an important problem in the elderly. This study focuses on the solutions that would move the negative effects of stature's reduction on BMI in elderly people. In this sense, it is one of the most reasonable solutions to estimate the body height using the anthropometric variables that show the least change during the old ages. The present study tries to develop alternative stature estimation equations using various extremity length measures. While designing the study, it was decided to take measurements in two groups, one of which was defined as "Young Group" (20-35 years) and the other as "Older Group" (65+ years). The study was carried out by taking the anthropometric measurements of 325 participants from the elderly group and 95 participants from the young group (420 in total). The study group was formed to form the formulas created as a result of the regression analysis, and the test group was formed to test the reliability of the equations obtained. The sociodemographic data of the sample reveal that the studied group is predominantly composed of participants from lower socioeconomic levels. The analysis made reveal that significant changes occur in both stature and body weight with old age. The results of correlation and regression analysis showed that the length of upper extremity, knee height, and tibia length are the variables changes minimally during old ages. With the help of regression equations created using these variables, new stature estimates were reached and then BMI values were calculated again. When the BMI values calculated from the measured height were compared with the estimated ones, it was seen that the corrected BMI values smaller than values on average compared to the old ones. In conclusion, it seems a reasonable approach to estimate body height from these variables by measuring extremity lengths, which can be an alternative to measured body height, in old age groups. The findings of our study revealed that the upper extremity length, tibia length, and knee height, respectively, are the most appropriate anthropometric measurements in this sense.