The objective of this study was to compare the bone mineral density (BMD) of men with Down syndrome (DS) to otherwise mentally retarded (MR) men and to investigate whether leg muscle strength of these patients is related to BMD. Two groups with MR (with and without DS) participated in the study, having met the following criteria: similar age, moderate to mild mental retardation, Tanner stage V of sexual development, similar age of beginning to walk, and equal motor activities. The DS group consisted of 8 men 23.9 +/- 4.2 years, and the MR group without DS consisted of 8 men 23.5 +/- 3.6 years. The two groups were compared with 10 sedentary students of the same age range (25.9 +/- 2.9 years) attending our University. The BMD of the 2(nd) to 4(th) lumbar vertebrae was measured in the PA projection and the mean density was expressed as g/cm(2). The isokinetic muscle strength of the right quadriceps femoris and hamstrings muscles was measured on a Cybex II isokinetic dynamometer. The value measured was peak torque at angular velocities at 60, 120, and 300 degrees.sec(-1). The results showed that BMD in DS individuals versus young adults (reference group of the scanner) was lower at the 26% level (T-score - 2.66 +/- 0.29) and significantly lower (P = 0.002) than that of the MR group. Significantly different muscle strength was observed between the DS and non-DS MR group (in quadriceps at 300 degrees.s(-1): P < 0.01, at 120 and 60 degrees. s(-1): P < 0.05; in hamstrings at 300 degrees.s(-1): P < 0.05). Higher differences in muscle strength were found between MR and control men, but no significant difference existed in BMD between them. Bivariate correlation showed that quadriceps strength significantly predicted the BMD in the DS patients. Active lifestyle and increased physical exercise to improve muscular strength should be instituted to avoid the development of osteoporosis in DS patients.
The objective of the study was to elucidate if individuals with Down's syndrome (DS) are likely to experience an increased risk of osteoporosis with advancing age, in addition to precocious aging and their skeletal anomalies. Bone mineral density (BMD) was measured in 22 home-reared adults (9 males and 13 females; age 26.22 +/- 4.45 and 23.65 +/- 3.23 years, respectively) by dual energy X-ray absorptiometry (DXA). The BMD of the second to fourth lumbar vertebrae was measured in posteroanterior projection and the mean density expressed as grams per square centimetre. The BMD of DS individuals was compared with 27 control subjects (12 males and 15 females) of the same age (age 24.16 +/- 3.46 and 23.86 +/- 2.92 years, respectively). The results showed that the BMD of the lumbar spine in the males as well as in the females with DS was significantly lower than that in their control counter-parts (p < 0.001). Comparing the DS males with the females, the BMD was lower in the males at a level of 9%. Factors that contribute to this disorder may be mainly the muscular hypotonia, the sedentary life-style and the accompanying diseases which frequently observed in the syndrome. Future studies must be focused on the biochemistry of bone metabolism, the evaluation of gonadal, thyroid and parathyroid function, and the genes of the extra chromosome 21.
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