Diverging results of areal and volumetric bone mineral density in Down syndrome.

M García-Hoyos,D De Luis,C Valero,M T García-Unzueta,J A Riancho

doi:10.1007/s00198-016-3814-1

Abstract

Patients with DS have a number of risk factors that could predispose them to osteoporosis. Several studies reported that people with DS also have lower areal bone mineral density, but differences in the skeletal size could bias the analysis. Seventy-five patients with DS and 76 controls without intellectual disability were recruited. Controls were matched for age and sex. Bone mineral density (BMD) was measure by Dual-energy X-ray Absorptiometry (DXA), and volumetric bone mineral density (vBMD) was calculated by published formulas. Body composition was also measured by DXA. Microarchitecture was measured by TBS and QUS. Serum 25-hidroxyvitamin D (25OHD), parathyroid hormone (PTH), aminoterminal propeptide of type collagen (P1NP), and C-terminal telopeptide of type I collagen (CTX) were also determined. Physical activity was assessed by the International Physical Activity Questionnaires (IPAQ-short form). To evaluate nutritional intake, we recorded three consecutive days of food. DS individuals had lower height (151±11 vs. 169±9cm). BMD was higher in the controls (lumbar spine (LS) 0.903±0.124g/cm2 in patients and 0.997±0.115g/cm2 in the controls; femoral neck (FN) 0.761±.126g/cm2 and 0.838±0.115g/cm2, respectively). vBMD was similar in the DS group (LS 0.244±0.124g/cm3; FN 0.325±.0.073g/cm3) and the controls (LS 0.255±0.033g/cm3; FN 0.309±0.043g/cm3). Microarchitecture measured by QUS was slightly better in DS, and TBS measures were similar in both groups. 25OHD, PTH, and CTX were similar in both groups. P1NP was higher in the DS group. Time spent on exercise was similar in both groups, but intensity was higher in the control group. Population with DS has correct nutrition. Areal BMD is reduced in DS, but it seems to be related to the smaller body and skeletal size. In fact, the estimated volumetric BMD is similar in patients with DS and in control individuals. Furthermore, people with DS have normal bone microarchitecture.

Highlights

Down syndrome (DS) is the most common intellectual disability and the most frequent chromosomal abnormality among live births[1,2,3]
In a previous study we found that skeletal size differences were largely responsible for the apparent differences in areal BMD (aBMD) between patients with DS and normal individuals
In the present study we aimed to confirm those results in a larger group of individuals with DS, to provide the reference ranges of aBMD in this population and to analyze the nutritional, anthropometric and lifestyle factors determining bone mass

Summary

Introduction

Down syndrome (DS) is the most common intellectual disability and the most frequent chromosomal abnormality among live births[1,2,3]. Patients with DS have a number of risk factors that theoretically could predispose them to osteoporosis, such as reduced muscle tone and physical activity, limited sun exposure (due to institutionalization, physical disabilities or skin diseases4), frequent comorbidities (thyroid disorders, hypogonadism, celiac disease, etc.), and drug therapies (corticoid or antiepileptic)[5,6]. Several studies[7,8,9] reported that people with DS have lower areal bone mineral density (BMD), but few of them have taken into account the morphological differences of bone, and the differences in bone size. In a previous study we found that skeletal size differences were largely responsible for the apparent differences in aBMD between patients with DS and normal individuals. In the present study we aimed to confirm those results in a larger group of individuals with DS, to provide the reference ranges of aBMD in this population and to analyze the nutritional, anthropometric and lifestyle factors determining bone mass

Objectives

Results

Conclusion