Child Health Needs and the Pediatric Rheumatology Workforce: 2020-2040

The Pediatric Rheumatology (PRH) workforce supply in the United States does not meet the needs of children. Lack of timely access to PRH care is associated with poor outcomes for children with rheumatic diseases. This article is part of a Pediatrics supplement focused on anticipating the future pediatric subspecialty workforce supply. It draws on information in the literature, American Board of Pediatrics data, and findings from a model that estimates the future supply of pediatric subspecialists developed by the Sheps Center for Health Services Research at the University of North Carolina at Chapel Hill, Strategic Modeling and Analysis Ltd., and the American Board of Pediatrics Foundation. PRH has a smaller workforce per capita of children than most other pediatric subspecialties. The model demonstrates that the clinical workforce equivalent of pediatric rheumatologists in 2020 was only 0.27 per 100 000 children, with a predicted increase to 0.47 by 2040. Although the model predicts a 72% increase in providers, this number remains inadequate to provide sufficient care given the number of children with rheumatic diseases, especially in the South and West regions. The likely reasons for the workforce shortage are multifactorial, including lack of awareness of the field, low salaries compared with most other medical specialties, concerns about working solo or in small group practices, and increasing provider retirement. Novel interventions are needed to increase the workforce size. The American College of Rheumatology has recognized the dire consequences of this shortage and has developed a workforce solutions initiative to tackle these problems.

Child Health Needs and the Pediatric Nephrology Subspecialty Workforce: 2020-2040

Pediatric nephrology is dedicated to caring for children with kidney disease, a unique blend of acute care and chronic longitudinal patient relationships. Though historically a small field, trainee interest has declined over the past 2 decades. This has led to growing alarm about the health of the pediatric nephrology workforce, although concerns have been hampered by a lack of available data to enable feasible projections. This article is part of a supplement that anticipates the future pediatric subspecialty workforce supply. It draws on existing literature, data from the American Board of Pediatrics, and findings from a model that estimates the future supply of pediatric subspecialists developed by the Carolina Health Workforce Research Center at the University of North Carolina Chapel Hill's Cecil G. Sheps Center for Health Services Research and Strategic Modeling Analytics & Planning Ltd. The workforce projections from 2020 to 2040 incorporate population growth, clinical effort, and geographic trends and model alternate scenarios adjusting for changes in trainee interest, clinical efforts, and workforce attrition. The baseline model predicts growth of clinical work equivalents by 26% by 2040, but further widening geographic disparities worsen the existing mismatch between supply, clinical need, and market demand. The worst-case scenario projects 13% growth by 2040 which, at best, maintains the status quo of an already strained workforce. The models do not account for many factors expected to heighten demand over the coming decades. Urgent reforms are necessary now. Proposed solutions require multipronged changes in education and training pathways, remuneration, clinical practice models, and government policy.

Child Health Needs and the Pediatric Endocrinology Workforce: 2020-2040

The pediatric endocrinology (PE) workforce in the United States is struggling to sustain an adequate, let alone optimal, workforce capacity. This article, one of a series of articles in a supplement to Pediatrics, focuses on the pediatric subspecialty workforce and furthers previous evaluations of the US PE workforce to model the current and future clinical PE workforce and its geographic distribution. The article first discusses the children presenting to PE care teams, reviews the current state of the PE subspecialty workforce, and presents projected headcount and clinical workforce equivalents at the national, census region, and census division level on the basis of a subspecialty workforce supply model through 2040. It concludes by discussing the educational and training, clinical practice, policy, and future workforce research implications of the data presented. Data presented in this article are available from the American Board of Pediatrics, the National Resident Matching Program, and the subspecialty workforce supply model. Aging, part-time appointments, and unbalanced geographic distribution of providers diminish the PE workforce capacity. In addition, limited exposure, financial concerns, and lifestyle perceptions may impact trainees. Additional workforce challenges are the subspecialty's increasingly complex cases and breadth of conditions treated, reliance on international medical graduates to fill fellowship slots, and high relative proportion of research careers. The recent limitations on pediatric endocrinologists providing gender-affirming care may also impact the geographic distribution of the subspecialty's workforce. Deliberate actions need to be taken now to continue serving the needs of children.

Child Health and the US Pediatric Subspecialty Workforce: Planning for the Future

This article opens a multi-article Pediatrics supplement that provides a rigorous analysis of the projected pediatric subspecialty workforce in the United States. Congenital variations, epigenetics, exposures, lifestyle, preventive care, and medical interventions from conception through young adulthood set the stage for health and wellbeing in adulthood. Although care provided by pediatric subspecialists is associated with better outcomes and lower costs compared with adult providers, the authors of recent articles in the lay and medical literature have questioned the capacity of pediatric subspecialists to meet children's health care needs. This article highlights that, despite numerous advances in prevention, diagnosis, and treatment, the last decade has witnessed increasing numbers of children with acute or chronic physical and mental health disorders, including medical complexity, obesity, type 2 diabetes, anxiety, depression, and suicidality, all of which are exacerbated by poverty, racism, and other social drivers of health. In this article, we then describe the variability in the demographics, practice characteristics, and geographic distribution of the 15 core pediatric subspecialties certified by the American Board of Pediatrics. We then discuss the rationale and approach to the development of a pediatric subspecialty workforce model that forecasts subspecialist supply from 2020 to 2040 for 14 subspecialties at the national and subnational levels (not including the newest subspecialty, pediatric hospital medicine), accounting for US Census Bureau child population projections. The model does not account for the unique physical and mental needs of individual children, nor does it address the increasingly precarious commitment to, and financing of, pediatric subspecialty care in the US health care system impacting market demand.

Projecting the Future Pediatric Subspecialty Workforce: Summary and Recommendations

This article summarizes the findings of a Pediatrics supplement addressing the United States workforce for 15 pediatric subspecialties. It includes results from a microsimulation model projecting supply through 2040; growth is forecasted to be uneven across the subspecialties with worsening geographic maldistribution. Although each subspecialty has unique characteristics, commonalities include (1) the changing demographics and healthcare needs of children, including mental health; (2) poor outcomes for children experiencing adverse social drivers of health, including racism; and (3) dependence on other subspecialties. Common healthcare delivery challenges include (1) physician shortages for some subspecialties; (2) misalignment between locations of training programs and subspecialists and areas of projected child population growth; (3) tension between increasing subsubspecialization to address rare diseases and general subspecialty care; (4) the need to expand clinical reach through collaboration with other physicians and advanced practice providers; (5) the lack of parity between Medicare, which funds much of adult care, and Medicaid, which funds over half of pediatric subspecialty care; and (6) low compensation of pediatric subspecialists compared with adult subspecialists. Overall, subspecialists identified the lack of a central authority to monitor and inform child healthcare provided by pediatric subspecialists as a challenge. Future research on the pediatric subspecialty workforce and the children it serves will be necessary to ensure these children's needs are met. Together, these articles provide overarching and subspecialty-specific recommendations to improve training, recruitment, and retention of a diverse workforce, implement innovative models of care, drive policy changes, and advise future research.

Association of Fibroblast Growth Factor 23 with Blood Pressure in Primary Proteinuric Glomerulopathies

INTRODUCTION

Fibroblast growth factor 23 (FGF23) has direct effects on the vasculature and myocardium, and high levels of FGF23 are a risk factor for cardiovascular disease (CVD); however, the impact of FGF23 on CVD in primary proteinuric glomerulopathies has not been addressed.

METHODS

The associations of baseline plasma intact FGF23 levels with resting blood pressure (BP) and lipids over time among adults and children with proteinuric glomerulopathies enrolled in the Nephrotic Syndrome Study Network (NEPTUNE) were analyzed using generalized estimating equation regression analyses. Models were adjusted for age, sex, glomerular diagnosis, follow-up time, estimated glomerular filtration rate, urine protein/creatinine ratio, obesity, and serum phosphorous levels.

RESULTS

Two hundred and four adults with median FGF23 77.5 (IQR 51.3-119.3) pg/mL and 93 children with median FGF23 62.3 (IQR 44.6-83.6) pg/mL were followed for a median of 42 (IQR 20.5-54) months. In adjusted models, each 1 µg/mL increase in FGF23 was associated with a 0.3 increase in systolic BP index at follow-up (p < 0.001). Greater baseline FGF23 was associated with greater odds of hypertensive BP (OR = 1.0003; 95% CI 1.001-1.006, p = 0.03) over time. Compared to tertile 1, tertile 2 (OR = 2.1; 95% CI 1.12-3.99, p = 0.02), and tertile 3 (OR = 3; 95% CI 1.08-8.08, p = 0.04), FGF23 levels were associated with greater odds of hypertensive BP over time. Tertile 2 was associated with greater triglycerides compared to tertile 1 (OR = 48.1; 95% CI 4.4-91.9, p = 0.03).

CONCLUSION

Overall, higher baseline FGF23 was significantly associated with hypertensive BP over time in individuals with proteinuric glomerulopathies. Further study of FGF23 as a therapeutic target for reducing CVD in proteinuric glomerular disease is warranted.

Strength training is more effective than aerobic exercise for improving glycaemic control and body composition in people with normal-weight type 2 diabetes: a randomised controlled trial

AIMS/HYPOTHESIS

Type 2 diabetes in people in the healthy weight BMI category (<25 kg/m2), herein defined as 'normal-weight type 2 diabetes', is associated with sarcopenia (low muscle mass). Given this unique body composition, the optimal exercise regimen for this population is unknown.

METHODS

We conducted a parallel-group RCT in individuals with type 2 diabetes (age 18-80 years, HbA1c 47.5-118.56 mmol/mol [6.5-13.0%]) and BMI <25 kg/m2). Participants were recruited in outpatient clinics or through advertisements and randomly assigned to a 9 month exercise programme of strength training alone (ST), aerobic training alone (AER) or both interventions combined (COMB). We used stratified block randomisation with a randomly selected block size. Researchers and caregivers were blinded to participants' treatment group; however, participants themselves were not. Exercise interventions were conducted at community-based fitness centres. The primary outcome was absolute change in HbA1c level within and across the three groups at 3, 6 and 9 months. Secondary outcomes included changes in body composition at 9 months. Per adherence to recommended exercise protocol (PP) analysis included participants who completed at least 50% of the sessions.

RESULTS

Among 186 individuals (ST, n=63; AER, n=58; COMB, n=65) analysed, the median (IQR) age was 59 (53-66) years, 60% were men and 83% were Asian. The mean (SD) HbA1c level at baseline was 59.6 (13.1) mmol/mol (7.6% [1.2%]). In intention-to-treat analysis, the ST group showed a significant decrease in HbA1c levels (mean [95% CI] -0.44 percentage points [-0.78, -0.12], p=0.002), while no significant change was observed in either the COMB group (-0.35 percentage points, p=0.13) or the AER group (-0.24 percentage points, p=0.10). The ST group had a greater improvement in HbA1c levels than the AER group (p=0.01). Appendicular lean mass relative to fat mass increased only in the ST group (p=0.0008), which was an independent predictor of HbA1c change (beta coefficient -7.16, p=0.01). Similar results were observed in PP analysis. Only one adverse event, in the COMB group, was considered to be possibly associated with the exercise intervention.

CONCLUSIONS/INTERPRETATION

In normal-weight type 2 diabetes, strength training was superior to aerobic training alone, while no significant difference was observed between strength training and combination training for HbA1c reduction. Increased lean mass relative to decreased fat mass was an independent predictor of reduction in HbA1c level.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02448498.

FUNDING

This study was funded by the National Institutes of Health (NIH; R01DK081371).

Recommendations for High-resolution Peripheral Quantitative Computed Tomography Assessment of Bone Density, Microarchitecture, and Strength in Pediatric Populations

PURPOSE OF REVIEW

The purpose of this review is to summarize current approaches and provide recommendations for imaging bone in pediatric populations using high-resolution peripheral quantitative computed tomography (HR-pQCT).

RECENT FINDINGS

Imaging the growing skeleton is challenging and HR-pQCT protocols are not standardized across centers. Adopting a single-imaging protocol for all studies is unrealistic; thus, we present three established protocols for HR-pQCT imaging in children and adolescents and share advantages and disadvantages of each. Limiting protocol variation will enhance the uniformity of results and increase our ability to compare study results between different research groups. We outline special cases along with tips and tricks for acquiring and processing scans to minimize motion artifacts and account for growing bone. The recommendations in this review are intended to help researchers perform HR-pQCT imaging in pediatric populations and extend our collective knowledge of bone structure, architecture, and strength during the growing years.

Vitamin D Metabolites and Risk of Cardiovascular Disease in Chronic Kidney Disease: The CRIC Study

Background The ratio of 24,25-dihydroxyvitamin D3/25-hydroxyvitamin D3 (vitamin D metabolite ratio [VDMR]) may reflect functional vitamin D activity. We examined associations of the VDMR, 25-hydroxyvitamin D (25[OH]D), and 1,25-dihydroxyvitamin D (1,25[OH]2D) with cardiovascular disease (CVD) in patients with chronic kidney disease. Methods and Results This study included longitudinal and cross-sectional analyses of 1786 participants from the CRIC (Chronic Renal Insufficiency Cohort) Study. Serum 24,25-dihydroxyvitamin D3, 25(OH)D, and 1,25(OH)2D were measured by liquid chromatography-tandem mass spectrometry 1 year after enrollment. The primary outcome was composite CVD (heart failure, myocardial infarction, stroke, and peripheral arterial disease). We used Cox regression with regression-calibrated weights to test associations of the VDMR, 25(OH)D, and 1,25(OH)2D with incident CVD. We examined cross-sectional associations of these metabolites with left ventricular mass index using linear regression. Analytic models adjusted for demographics, comorbidity, medications, estimated glomerular filtration rate, and proteinuria. The cohort was 42% non-Hispanic White race and ethnicity, 42% non-Hispanic Black race and ethnicity, and 12% Hispanic ethnicity. Mean age was 59 years, and 43% were women. Among 1066 participants without prevalent CVD, there were 298 composite first CVD events over a mean follow-up of 8.6 years. Lower VDMR and 1,25(OH)2D were associated with incident CVD before, but not after, adjustment for estimated glomerular filtration rate and proteinuria (hazard ratio, 1.11 per 1 SD lower VDMR [95% CI, 0.95-1.31]). Only 25(OH)D was associated with left ventricular mass index after full covariate adjustment (0.6 g/m2.7 per 10 ng/mL lower [95% CI, 0.0-1.3]). Conclusions Despite modest associations of 25(OH)D with left ventricular mass index, 25(OH)D, the VDMR, and 1,25(OH)2D were not associated with incident CVD in chronic kidney disease.

Vitamin D supplementation in children and young adults with persistent proteinuria secondary to glomerular disease

BACKGROUND

Vitamin D deficiency is common in glomerular disease. Supplementation may be ineffective due to ongoing urinary losses of vitamin D binding protein. We sought to determine if daily cholecalciferol supplementation would increase vitamin D concentrations in children with glomerular disease and persistent proteinuria, without adverse effects.

METHODS

Eighteen participants at least 5 years of age with primary glomerular disease and urine protein:creatinine ratio ≥ 0.5 were enrolled from four pediatric nephrology practices to receive cholecalciferol supplementation: 4,000 IU or 2,000 IU per day for serum 25 hydroxyvitamin vitamin D (25OHD) concentrations < 20 ng/mL and 20 ng/mL to < 30 ng/mL, respectively. Measures of vitamin D and mineral metabolism were obtained at baseline and weeks 6 and 12. Multivariable generalized estimating equation (GEE) regression estimated mean percent changes in serum 25OHD concentration.

RESULTS

Median baseline 25OHD was 12.8 ng/mL (IQR 9.3, 18.9) and increased to 27.8 ng/mL (20.5, 36.0) at week 6 (p < 0.001) without further significant increase at week 12. A total of 31% of participants had a level ≥ 30 ng/mL at week 12. Supplementation was stopped in two participants at week 6 for mildly elevated calcium and phosphorus, respectively, with subsequent declines in 25OHD of > 20 ng/mL. In the adjusted GEE model, 25OHD was 102% (95% CI: 64, 141) and 96% (95% CI: 51, 140) higher versus baseline at weeks 6 and 12, respectively (p < 0.001).

CONCLUSION

Cholecalciferol supplementation in vitamin D deficient children with glomerular disease and persistent proteinuria safely increases 25OHD concentration. Ideal dosing to fully replete 25OHD concentrations in this population remains unknown.

CLINICAL TRIAL

NCT01835639. A higher resolution version of the Graphical abstract is available as Supplementary information.

Cystatin C and Creatinine Concentrations are Uninformative Biomarkers of Sarcopenia: A Cross-Sectional NHANES Study

OBJECTIVES

Differences in creatinine and cystatin C-based estimates of glomerular filtration rate (eGFR_Diff = eGFR_Cr - eGFR_CysC) may reflect differences in muscle mass. We sought to determine if eGFR_Diff (1) reflects lean mass, (2) identifies sarcopenic individuals beyond estimates based on age, BMI, and sex; and (3) demonstrates associations differently in those with and without chronic kidney disease (CKD).

DESIGN AND METHODS

This cross-sectional study included 3,754 participants, ages 20-85 years, with creatinine and cystatin C concentration levels, and DXA scans from NHANES data (1999 to 2006). DXA appendicular lean mass index (ALMI) estimated muscle mass. Non-race-based CKD EPI equations estimated GFR using creatinine (eGFR_Cr), cystatin C (eGFR_CysC), and both biomarkers (eGFR_CysC&Cr). CKD was defined as eGFR_CysC&Cr < 60 mL/min/1.73m². ALMI sex-specific T-scores (compared with young adult) < -2.0 defined sarcopenia. In estimating ALMI, we compared the coefficient of determination (R²) values from: 1) eGFR_Diff, 2) clinical characteristics (age, BMI, and sex), and 3) clinical characteristics plus eGFR_Diff. Using logistic regression, we evaluated each model's C-statistic to diagnose sarcopenia.

RESULTS

eGFR_DIFF was negatively and weakly associated with ALMI (No CKD: R² = 0.006, p-value 0.002; CKD: R² = 0.001, p-value 0.9). Clinical characteristics explained most of the variation in ALMI (No CKD: R² = 0.851, CKD: R² = 0.828), and provided strong discrimination of sarcopenia (No CKD C-statistic: 0.950; CKD C-statistic: 0.943). Adding eGFR_Diff improved the R² by 0.025, and the C-statistic by 0.003. Tests for interaction between eGFR_Diff and CKD were not significant (all p-values > 0.05).

CONCLUSIONS

Although eGFR_Diff has statistically significant associations with ALMI and sarcopenia in univariate analyses, multivariate analyses demonstrate that eGFR_Diff does not capture more information beyond routine clinical characteristics (age, BMI, and sex).

Trabecular Bone Score (TBS) Varies with Correction for Tissue Thickness Versus Body Mass Index: Implications When Using Pediatric Reference Norms

Trabecular bone score (TBS) derived from secondary analysis of lumbar spine dual-energy X-ray absorptiometry (DXA) scans improves fracture prediction independent of bone mineral density (BMD) in adults. The utility of TBS to assess fracture risk in younger patients has not been established because pediatric norms have been lacking. Robust TBS reference data from the Bone Mineral Density in Childhood Study (BMDCS) have been published. TBS values for the BMDCS study were derived using an algorithm that accounts for tissue thickness (TBS_TH ) rather than the commercially available algorithm that adjusts for body mass index (BMI; TBS_BMI ). We examined the magnitude of differences in TBS_TH and TBS_BMI in a cohort of 189 healthy youth. TBS values using both algorithms increased with age and pubertal development in a similar pattern. However, TBS_BMI values were systematically and significantly higher than TBS_TH (mean = 0.06, p < 0.0001). The difference between calculated TBS_BMI and TBS_TH was not uniform. Differences were greater at lower TBS values, in males, in older individuals, in those at later Tanner stages, and in those with a greater BMI Z-score. These systematic differences preclude the development of a simple formula to allow conversion of TBS_BMI to TBS_TH "equivalents." Because of these systematic differences in these two algorithms, using an individual's TBS_BMI to calculate a Z-score using the BMDCS TBS_TH reference values results in a falsely higher TBS Z-score (differences mean = 0.73, interquartile range [IQR] = 0.3 to 1.6). Until TBS_TH software for Hologic DXA equipment becomes commercially available, BMDCS TBS reference norms should not be used. © 2023 American Society for Bone and Mineral Research (ASBMR).

Challenging obesity and sex based differences in resting energy expenditure using allometric modeling, a sub-study of the DIETFITS clinical trial

BACKGROUND & AIMS

Resting energy expenditure (REE) is a major component of energy balance. While REE is usually indexed to total body weight (BW), this may introduce biases when assessing REE in obesity or during weight loss intervention. The main objective of the study was to quantify the bias introduced by ratiometric scaling of REE using BW both at baseline and following weight loss intervention.

DESIGN

Participants in the DIETFITS Study (Diet Intervention Examining The Factors Interacting with Treatment Success) who completed indirect calorimetry and dual-energy X-ray absorptiometry (DXA) were included in the study. Data were available in 438 participants at baseline, 340 at 6 months and 323 at 12 months. We used multiplicative allometric modeling based on lean body mass (LBM) and fat mass (FM) to derive body size independent scaling of REE. Longitudinal changes in indexed REE were then assessed following weight loss intervention.

RESULTS

A multiplicative model including LBM, FM, age, Black race and the double product (DP) of systolic blood pressure and heart rate explained 79% of variance in REE. REE indexed to [LBM^0.66 × FM^0.066] was body size and sex independent (p = 0.91 and p = 0.73, respectively) in contrast to BW based indexing which showed a significant inverse relationship to BW (r = -0.47 for female and r = -0.44 for male, both p < 0.001). When indexed to BW, significant baseline differences in REE were observed between male and female (p < 0.001) and between individuals who are overweight and obese (p < 0.001) while no significant differences were observed when indexed to REE/[LBM^0.66 × FM^0.066], p > 0.05). Percentage predicted REE adjusted for LBM, FM and DP remained stable following weight loss intervention (p = 0.614).

CONCLUSION

Allometric scaling of REE based on LBM and FM removes body composition-associated biases and should be considered in obesity and weight-based intervention studies.

Bone accrual and structural changes over one year in youth with cystic fibrosis

Background

Pediatric bone accrual governs peak bone mass and strength. Longitudinal studies of bone health in youth with cystic fibrosis (CF) may provide insight into CF-related bone disease (CFBD), a prevalent co-morbidity in adults with CF.

Methods

This one-year longitudinal study of youth with pancreatic insufficient CF, enrolled in a nutrition intervention study [n = 62 (36 M/26F)] 1) examined dual-energy x-ray absorptiometry (DXA)-defined lumbar spine (LS) and total body less head (TBLH) bone accrual and 2) compared their changes in peripheral quantitative computed tomography (pQCT) cortical and trabecular tibial bone density and geometry to those of a healthy reference group [n = 143 (68 M/75F)].

Main outcome measures were 1) DXA: lumbar spine areal bone mineral density (LSaBMD) and total body less head bone mineral content (TBLH-BMC), sex- and pubertal status-specific, height velocity (HV)-adjusted or HV and lean body mass velocity (HV-LBMV)-adjusted annualized velocity-Z scores and 2) pQCT: age, sex, pubertal status and, when appropriate, tibial length adjusted Z-scores for bone architecture measures.

DXA velocity-Z were compared to expected mean of 0 and correlations with clinical parameters (age, BMI-Z and FEV₁%-predicted) tested. Within-subject comparisons of HV-adjusted and LBMV-HV-adjusted DXA velocity-Z were conducted in CF.

pQCT Z-scores were compared between the two groups over one year using longitudinal models. Longitudinal relationships between measures of bone health and clinical parameters (age, BMI-Z and FEV₁%-predicted) were examined in individuals with CF.

Results

DXA velocity-Z were higher than normal in females (p < 0.05) but not males with CF. HV-adjusted and LBMV-HV-adjusted velocity-Z did not differ for LSaBMD or TBLH-BMC.

In males with CF, both HV-adjusted and LBMV-HV-adjusted LSaBMD velocity-Z scores correlated negatively with age (HV rho: −0.35; p = 0.045 and LBMV-HV rho: −0.47; p = 0.0046). In males with CF BMI-Z correlated positively with HV-adjusted LSaBMD velocity-Z (rho: 0.37; p = 0.034), but this relationship did not persist for LBMV-HV (rho: 0.14; p = 0.42). In females with CF, no correlations between LSaBMD velocity-Z scores and age or BMI-Z were found (all p > 0.05). No correlations between LSaBMD velocity-Z scores and FEV₁%-predicted were seen in either sex (all p > 0.12). TBLH-BMC velocity Z-scores were not correlated with clinical parameters in either sex (all p > 0.1).

At baseline, multiple pQCT parameters were lower in CF (p < 0.05). pQCT Z-scores did not differ between baseline and one-year in either CF or reference group. In a longitudinal model comparing pQCT-Z changes in CF and reference, multiple pQCT-Z outcomes remained lower in CF, but the changes in parameters did not differ in CF vs reference (all p > 0.26). Lower pQCT outcomes in CF were largely restricted to males (CF group*female sex interaction beta coefficients > 0). In this combined longitudinal model, of both CF and reference, BMI-Z was positively associated with pQCT-Z parameters(p < 0.001).

Multiple pQCT-Z outcomes positively correlated with both BMI-Z and FEV₁%-predicted in males with CF, and with FEV₁%-predicted in females with CF (p < 0.05). Age was negatively associated with section modulus (p = 0.001) in males and with cortical density-Z in females (p < 0.001).

Conclusions

With improved longevity, bone health in CF is of increasing importance. On average, bone accrual was preserved in youth with CF, and while deficits in bone geometry and strength were found, these deficits did not worsen over the one-year study. Lower LS bone accrual with increasing age suggests emerging adulthood is a period of vulnerability in CF while the role of LBM in bone health is underscored by the lack of relationship between LBMV-adjusted accrual and BMI. These findings may be useful in targeting screening practices and interventions.

Persistent Musculoskeletal Deficits in Pediatric, Adolescent and Young Adult Survivors of Allogeneic Hematopoietic Stem-Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a common therapy for pediatric hematologic malignancies. With improved supportive care, addressing treatment-related late effects is at the forefront of survivor long-term health and quality of life. We previously demonstrated that alloHSCT survivors had increased adiposity, decreased lean mass, and lower bone density and strength, 7 years (median) from alloHSCT compared to their healthy peers. Yet it is unknown whether these deficits persist. Our longitudinal study characterized changes in muscle and bone over a period of 3.4 (range, 2.0 to 4.9) years in 47 childhood alloHSCT survivors, age 5-26 years at baseline (34% female). Tibia cortical bone geometry and volumetric density and lower leg muscle cross-sectional area (MCSA) were assessed via peripheral quantitative computed tomography (pQCT). Anthropometric and pQCT measurements were converted to age, sex, and ancestry-specific standard deviation scores, adjusted for leg length. Muscle-specific force was assessed as strength relative to MCSA adjusted for leg length (strength Z-score). Measurements were compared to a healthy reference cohort (n = 921), age 5-30 years (52% female). At baseline and follow-up, alloHSCT survivors demonstrated lower height Z-scores, weight Z-scores, and leg length Z-scores compared to the healthy reference cohort. Deficits in MCSA, trabecular volumetric bone density, and cortical bone size and estimated strength (section modulus) were evident in survivors (all p < 0.05). Between the two study time points, anthropometric, muscle, and bone Z-scores did not change significantly in alloHSCT survivors. Approximately 15% and 17% of alloHSCT survivors had MCSA and section modulus Z-score < -2.0, at baseline and follow-up, respectively. Furthermore, those with a history of total body irradiation compared to those without demonstrated lower MCSA at follow-up. The persistent muscle and bone deficits in pediatric alloHSCT survivors support the need for strategies to improve bone and muscle health in this at-risk population. © 2022 American Society for Bone and Mineral Research (ASBMR).

Deficits in the Functional Muscle-Bone Unit in Youths with Fontan Physiology

OBJECTIVE

To determine whether dual energy X-ray absorptiometry (DXA), a clinically available tool, mirrors the magnitude of deficits in trabecular and cortical bone mineral density (BMD) demonstrated on peripheral quantitative computed tomography in youth with Fontan physiology.

STUDY DESIGN

We aimed to describe DXA-derived BMD at multiple sites and to investigate the relationship between BMD and leg lean mass, a surrogate for skeletal muscle loading. Subjects with Fontan (n = 46; aged 5-20 years) underwent DXA in a cross-sectional study of growth and bone and muscle health as described previously. Data from the Bone Mineral Density in Childhood Study were used to calculate age-, sex-, and race-specific BMD z-scores of the whole body, lumbar spine, hip, femoral neck, distal one-third radius, ultradistal radius, and leg lean mass z-score (LLMZ).

RESULTS

Fontan BMD z-scores were significantly lower than reference at all sites-whole body, -0.34 ± 0.85 (P = .01); spine, -0.41 ± 0.96 (P = .008); hip, -0.75 ± 1.1 (P < .001); femoral neck, -0.73 ± 1.0 (P < .001); distal one-third radius, -0.87 ± 1.1 (P < .001); and ultradistal radius. -0.92 ± 1.03 (P < .001)-as was LLMZ (-0.93 ± 1.1; P < .001). Lower LLMZ was associated with lower BMD of the whole body (R² = 0.40; P < .001), lumbar spine (R² = 0.16; P = .005), total hip (R² = 0.32; P < .001), femoral neck (R² = 0.47; P < .001), and ultradistal radius (R² = 0.35; P < .001).

CONCLUSIONS

Patients with Fontan have marked deficits in both cortical (hip, distal one-third radius) and trabecular (lumbar spine, femoral neck, ultradistal radius) BMD. Lower LLMZ is associated with lower BMD and may reflect inadequate skeletal muscle loading. Interventions to increase muscle mass may improve bone accrual.

Sarcopenic Obesity in Rheumatoid Arthritis: Prevalence and Impact on Physical Functioning

OBJECTIVE

We determined the prevalence of sarcopenic obesity in patients with rheumatoid arthritis (RA) using multiple methods and assessed associations with physical functioning.

METHODS

This study evaluated data from three RA cohorts. Whole-body dual-energy absorptiometry (DXA) measures of appendicular lean mass index (ALMI, kg/m2) and fat mass index (FMI) were converted to age, sex, and race-specific Z-Scores and categorized using a recently validated method and compared it to a widely-used existing method. The prevalence of body composition abnormalities in RA was compared with two reference populations. In the RA cohorts, associations between body composition and change in the Health Assessment Questionnaire (HAQ) and the Short Physical Performance Battery (SPPB) in follow-up were assessed using linear and logistic regression, adjusting for age, sex, race, and study.

RESULTS

The prevalence of low lean mass and sarcopenic obesity were higher in patients with RA (14.2; 12.6%, respectively) compared with the reference population cohorts (7-10%; 4-4.5%, respectively, all p< 0.05). There was only moderate agreement among methods of sarcopenic obesity categorization (Kappa 0.45). The recently validated method categorized fewer subjects as obese, and many of these were categorized as low lean mass only. Low lean mass, obesity, and sarcopenic obesity were each associated with higher HAQ and lower SPPB at baseline and numerically greater worsening.

CONCLUSION

RA patients had higher rates of low lean mass and sarcopenic obesity than the general population. The recently validated methods characterized body composition changes differently from traditional methods and were more strongly associated with physical function.

Changes in Body Composition, Muscle Strength, and Fat Distribution Following Kidney Transplantation

RATIONALE AND OBJECTIVE

Low muscle mass relative to fat mass (relative sarcopenia) has been associated with mortality and disability but has not been examined following transplantation. We studied how measures of body composition change after receipt of a kidney allograft.

STUDY DESIGN

Prospective longitudinal cohort study.

SETTING AND PARTICIPANTS

60 kidney transplant recipients (ages 20-60 years) at the University of Pennsylvania.

EXPOSURE

Kidney transplantation.

OUTCOMES

DXA measures of fat mass index (FMI) and appendicular lean mass index (ALMI; representing muscle mass), CT measures of muscle density (low density represents increased intramuscular adipose tissue), dynamometer measures of leg muscle strength, and physical activity. ALMI relative to FMI (ALM_FMI) is an established index of relative sarcopenia.

ANALYTICAL APPROACH

Measures expressed as age, sex, and race-specific Z-scores for transplant recipients were compared to 327 healthy controls. Regression models were used to identify correlates of change in outcome Z-scores and compare transplant recipients to controls.

RESULTS

At transplantation, ALMI, ALMI_FMI, muscle strength and muscle density Z-scores were lower vs. controls (all p≤0.001). Transplant recipients received glucocorticoids throughout. The prevalence of obesity increased from 18 to 45%. Although ALMI increased following transplantation (p<0.001) and was comparable to controls from 6 months onward, gains were outpaced by increases in FMI, resulting in persistent ALMI_FMI deficits (mean Z-score -0.31 at 24 months, p=0.02 vs controls). Muscle density improved following transplantation despite gains in FMI (p = 0.02). Muscle strength relative to ALMI also improved (p = 0.04) but remained low compared with controls (p=0.01). Exercise increased in the early months following transplantation (p<0.05) but remained lower than controls (p=0.02).

LIMITATIONS

Lack of muscle biopsies precluded assessment of muscle histology and metabolism.

CONCLUSIONS

The two-year interval following kidney transplantation was characterized by gains in muscle mass and strength that were outpaced by gains in fat mass resulting in persistent relative sarcopenia.

Sarcopenia and preserved bone mineral density in paediatric survivors of high-risk neuroblastoma with growth failure

BACKGROUND

Survival from paediatric high-risk neuroblastoma (HR-NBL) has increased, but cis-retinoic acid (cis-RA), the cornerstone of HR-NBL therapy, can cause osteoporosis and premature physeal closure and is a potential threat to skeletal structure in HR-NBL survivors. Sarcopenia is associated with increased morbidity in survivors of paediatric malignancies. Low muscle mass may be associated with poor prognosis in HR-NBL patients but has not been studied in these survivors. The study objective was to assess bone density, body composition and muscle strength in HR-NBL survivors compared with controls.

METHODS

This prospective cross-sectional study assessed areal bone mineral density (aBMD) of the whole body, lumbar spine, total hip, femoral neck, distal 1/3 and ultradistal radius and body composition (muscle and fat mass) using dual-energy X-ray absorptiometry (DXA) and lower leg muscle strength using a dynamometer. Measures expressed as sex-specific standard deviation scores (Z-scores) included aBMD (adjusted for height Z-score), bone mineral apparent density (BMAD), leg lean mass (adjusted for leg length), whole-body fat mass index (FMI) and ankle dorsiflexion peak torque adjusted for leg length (strength-Z). Muscle-specific force was assessed as strength relative to leg lean mass. Outcomes were compared between HR-NBL survivors and controls using Student's t-test or Mann-Whitney U test. Linear regression models examined correlations between DXA and dynamometer outcomes.

RESULTS

We enrolled 20 survivors of HR-NBL treated with cis-RA [13 male; mean age: 12.4 ± 1.6 years; median (range) age at therapy initiation: 2.6 (0.3-9.1) years] and 20 age-, sex- and race-matched controls. Height-Z was significantly lower in HR-NBL survivors compared with controls (-1.73 ± 1.38 vs. 0.34 ± 1.12, P < 0.001). Areal BMD-Z, BMAD-Z, FMI-Z, visceral adipose tissue and subcutaneous adipose tissue were not significantly different in HR-NBL survivors compared with controls. Compared with controls, HR-NBL survivors had lower leg lean mass-Z (-1.46 ± 1.35 vs. - 0.17 ± 0.84, P < 0.001) and strength-Z (-1.13 ± 0.86 vs. - 0.15 ± 0.71, P < 0.001). Muscle-specific force was lower in HR-NBL survivors compared with controls (P < 0.05).

CONCLUSIONS

Bone mineral density and adiposity are not severely impacted in HR-NBL survivors with growth failure, but significant sarcopenia persists years after treatment. Future studies are needed to determine if sarcopenia improves with muscle-specific interventions in this population of cancer survivors.