Endocrine Abstracts

JOINT644

Modest decreases in height occur during normal aging, but usually have only a minimal effect on BMI (body mass index). Height loss may result from vertebral fractures, disc collapse, kyphosis, and/or scoliosis. Accurate determinations of BMI values are essential for prescribing diet and exercise regimens especially for adults with Prader-Willi syndrome (PWS). At the time of routine yearly visits to our national multidisciplinary PWS clinic, we measured standing heights in 28 PWS adults over a duration 11.3±3.4 (range 5.1 to 16.2) years. Most had no or only minimal height loss, but in four individuals measured heights decreased gradually over 7.9 to 16.1 years by 6.2, 6.6, 7.0, and 6.3 cm, respectively. Height loss for these four patients resulted in artifactually high BMI values compared to values based on the previously measured tallest heights. BMI values calculated by using the most recent heights compared to tallest height measurements were 41.4 vs 37.9, 31.9 vs 29.1, 31.0 vs 28.5, and 27.2 vs 24.8 kg/m², respectively. Adjustment of BMI for the tallest measured heights resulted in redefining obesity class from class III to class II in one individual, from obesity class I to "overweight" in two patients, and from overweight to normal in one man. Failure to recognize that an increase in BMI may be due to height loss rather than weight gain could lead to inappropriate recommendations for reduction in caloric intake. Even minor changes in diet restrictions can affect mood and behavior in individuals with PWS. Recognition of height loss as a contributing factor to BMI calculations is important for clinical studies evaluating effects of life-style changes and medical interventions for obesity.