COMPARISON OF ULTRASOUND MEASUREMENTS AT THE HEEL BETWEEN ADULTS WITHMENTAL-RETARDATION AND CONTROL SUBJECTS

Little is known about the prevalence of metabolic bone disease among a dults with mental retardation (now known as learning disability), alth ough they may be at increased risk of fractures. Broadband-ultrasound attenuation (BUA) and velocity-of-sound (VOS) measurements were perfor med on the left heel of 170 patients in a large hospital for adults wi th mental retardation, For 108 of these patients, age-and gender-match ed control subjects were recruited from the local community, who also underwent BUA and VOS measurements, The mean age of matched pairs of p atients and control subjects was 55 (range 32-83) years for men and 53 (range 27-82) years for women. Mean +/- SEM BUA for male patients was 52 +/- 4 dB/MHz and 89 +/- 2 for control subjects, whereas for female patients it was 34 +/- 3 dB/MHz and 68 +/- 2 for control subjects. VO S was 1603 +/- 7 m/sec for male patients and 1649 +/- 5 for control su bjects, and 1573 +/- 7 m/sec for female patients and 1623 +/- 5 for co ntrol subjects. All differences between patients and control subjects were significant (p < 0.005). Dual-energy X-ray absorptiometry bone mi neral density (BMD) measurements were also performed in seven patients with BUA less than 50 dB/MHz, four of whom mere found to have a lumba r spine or femoral neck BR-ID more than 2.5 SD below the mean value fo r young adults. This study shows that patients with mental retardation have a marked reduction in BUA and VOS measurements at the heel, comp ared with age-matched control subjects. There is a need to identify th e major causes of low bone mass in this group, as there may be potenti ally avoidable risk factors for osteoporosis, such as vitamin D defici ency and hypogonadism, (C) 1998 by Elsevier Science Inc. All rights re served.