Bone health in Down syndrome

Bone mineral density in adults with Down syndrome: a cross-sectional study in a Brazilian sample

BACKGROUND

We aim to investigate the relationship between bone mass in a sample of Brazilian individuals with DS and handgrip strength, body mass index (BMI) and physical exercise.

METHODS

Dual-energy X-ray emission densitometry analysis of bone mass in 26 individuals with DS (8 men and 18 women with a mean age of 30.7 ± 10.3 years) was conducted. Additionally, weight and height were measured to determine BMI, palmar grip strength was measured using a Jammar dynamometer®, and physical activity was classified using the International Physical Activity Questionnaire (IPAQ).

RESULTS

In this sample, 2/15 (13.3%) individuals with age between 18 to 29 years had low BMD in the spine; 2/8 (25%) of those with age between 30 and 39 years also had low BMD in the spine and 2/3 (66.6%) with age ≥40 had low BMD in the femur. There were significant correlations between palmar grip strength and Z femoral neck score in women (P = 0.02) and between BMI and Z femoral neck score in men (P = 0.04). All other correlations lacked statistical significance (P > 0.05).

CONCLUSIONS

Brazilian patients with DS showed a high prevalence of low bone mass. Traditional factors such as muscle strength, BMI and physical activity appear to have little effect on bone mineral density in this population.

Current Analysis of Skeletal Phenotypes in Down Syndrome

PURPOSE

Down syndrome (DS) is caused by trisomy 21 (Ts21) and results in skeletal deficits including shortened stature, low bone mineral density, and a predisposition to early onset osteoporosis. Ts21 causes significant alterations in skeletal development, morphology of the appendicular skeleton, bone homeostasis, age-related bone loss, and bone strength. However, the genetic or cellular origins of DS skeletal phenotypes remain unclear.

RECENT FINDINGS

New studies reveal a sexual dimorphism in characteristics and onset of skeletal deficits that differ between DS and typically developing individuals. Age-related bone loss occurs earlier in the DS as compared to general population. Perturbations of DS skeletal quality arise from alterations in cellular and molecular pathways affected by the overexpression of trisomic genes. Sex-specific alterations occur in critical developmental pathways that disrupt bone accrual, remodeling, and homeostasis and are compounded by aging, resulting in increased risks for osteopenia, osteoporosis, and fracture in individuals with DS.

Medical Care of Adults With Down Syndrome: A Clinical Guideline

IMPORTANCE

Down syndrome is the most common chromosomal condition, and average life expectancy has increased substantially, from 25 years in 1983 to 60 years in 2020. Despite the unique clinical comorbidities among adults with Down syndrome, there are no clinical guidelines for the care of these patients.

OBJECTIVE

To develop an evidence-based clinical practice guideline for adults with Down syndrome.

EVIDENCE REVIEW

The Global Down Syndrome Foundation Medical Care Guidelines for Adults with Down Syndrome Workgroup (n = 13) developed 10 Population/Intervention/ Comparison/Outcome (PICO) questions for adults with Down syndrome addressing multiple clinical areas including mental health (2 questions), dementia, screening or treatment of diabetes, cardiovascular disease, obesity, osteoporosis, atlantoaxial instability, thyroid disease, and celiac disease. These questions guided the literature search in MEDLINE, EMBASE, PubMed, PsychINFO, Cochrane Library, and the TRIP Database, searched from January 1, 2000, to February 26, 2018, with an updated search through August 6, 2020. Using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) methodology and the Evidence-to-Decision framework, in January 2019, the 13-member Workgroup and 16 additional clinical and scientific experts, nurses, patient representatives, and a methodologist developed clinical recommendations. A statement of good practice was made when there was a high level of certainty that the recommendation would do more good than harm, but there was little direct evidence.

FINDINGS

From 11 295 literature citations associated with 10 PICO questions, 20 relevant studies were identified. An updated search identified 2 additional studies, for a total of 22 included studies (3 systematic reviews, 19 primary studies), which were reviewed and synthesized. Based on this analysis, 14 recommendations and 4 statements of good practice were developed. Overall, the evidence base was limited. Only 1 strong recommendation was formulated: screening for Alzheimer-type dementia starting at age 40 years. Four recommendations (managing risk factors for cardiovascular disease and stroke prevention, screening for obesity, and evaluation for secondary causes of osteoporosis) agreed with existing guidance for individuals without Down syndrome. Two recommendations for diabetes screening recommend earlier initiation of screening and at shorter intervals given the high prevalence and earlier onset in adults with Down syndrome.

CONCLUSIONS AND RELEVANCE

These evidence-based clinical guidelines provide recommendations to support primary care of adults with Down syndrome. The lack of high-quality evidence limits the strength of the recommendations and highlights the need for additional research.

Analysis of volumetric BMD in people with Down syndrome using DXA-based 3D modeling

We analyzed volumetric bone mineral density, by 3D analysis, in 76 people with Down syndrome and 76 controls. People with Down syndrome, particularly men, have a lower hip volumetric bone mineral density than the general population. Besides, volumetric bone mineral density declines more rapidly in Down syndrome.

INTRODUCTION

People with Down syndrome (DS) have a lower areal bone mineral density (aBMD) estimated by dual-energy X-ray absorptiometry (DXA). However, they have smaller-sized bones, which could influence the measurements. Therefore, our objective was to determine volumetric BMD in these patients.

MATERIALS AND METHODS

We included 76 outpatients with DS and 76 control healthy volunteers matched for age and sex distribution. Clinical data were obtained with a standardized interview and physical exam, including age, sex, height, weight, and body mass index (BMI). aBMD was measured by dual-energy X-ray at the femoral neck (FN) and total hip (TH). The 3D-SHAPER® software (version 2.8, Galgo Medical, Barcelona, Spain) was used to derive 3D analysis from participants' hip DXA scans.

RESULTS

DS femurs had a similar 3D geometry, compared with the femurs of controls. However, 3D analysis showed that participants with DS had smaller cortical thickness (1.84 mm ± 0.17 vs. 2.02 ± 0.20 mm; p < 0.0001), cortical vBMD (777 ± 49 mg/cm³ vs. 809 ± 43 mg/cm³; p < 0.0001), and cortical sBMD (143 ± 19 mg/cm² vs. 164 ± 22 mg/cm²; p < 0.0001). After adjustment for age and BMI, all 3D measurements remained lower in DS than in controls. These differences were more marked in men than in women. vBMD decreased with age in controls and DS, but the decline was greater in DS for all 3D parameters.

CONCLUSION

People with DS, particularly men, have a lower hip vBMD than the general population. Besides, vBMD declines more rapidly in DS.