Effect of Frail Phenotype on Bone Mass and Vertebral Compression Fracture in Individuals Undergoing Dialysis
Journal
Journal of the American Geriatrics Society
Journal Volume
64
Journal Issue
9
Pages
e19-e21
Date Issued
2016
Author(s)
the COhort of GEriatric Nephrology in National Taiwan University Hospital (COGENT) study group
Abstract
To the Editor: Frailty denotes a decline in ability to manage physiological stressors with aging. Presence of frailty predicts the risk of clinically significant fractures, and frail individuals frequently have osteoporosis.1 Frailty and osteoporosis putatively share a common ground, including coexisting physical inactivity, muscle wasting, weight loss, and nutritional insufficiency.2 Frailty is also highly prevalent in individuals with end-stage renal disease (ESRD);3 its presence and severity are associated with poor outcomes.4 In addition, individuals with ESRD are at greater risk of hip fracture because of osteoporosis or the abnormal bony architecture resulting from chronic kidney disease–mineral and bone disorder (MBD; renal osteodystrophy).5 It is unclear whether the established association between frailty, osteoporosis, and fracture also exists in individuals with ESRD, in whom silent vertebral compression fractures (VCFs) are underrecognized.6 The purpose of this pilot study was to investigate the relationship between frailty, bone mass, and VCFs in individuals with ESRD. Forty-three individuals with ESRD were prospectively enrolled after providing informed consent (approved by National Taiwan University Hospital ethical review board, 201505154RINB). All participants completed a self-report frailty instrument (simple FRAIL scale (SFS), score range 0–5, with higher scores indicating greater frailty) with validated efficacy in individuals with ESRD7 and underwent blood tests for serum calcium, phosphate, alkaline phosphatase, and intact parathormone. Certified radiologists obtained and interpreted a thoracolumbar spinal roentgenogram to determine VCF status (location and segments). Thirty-seven (86%) underwent dual-energy X-ray absorptiometry (DXA; Hologic, Waltham, MA) for evaluation of bone mass (bone mineral content (BMC)/density (BMD), T/Z-scores). DXA and VCF results were stratified according to presence of frailty and analyzed accordingly. Of this cohort, 14% were frail (SFS ≥3) and 51% were prefrail (SFS 1–2). Thirteen (30%) had VCFs, and six (14%) had three or more VCF segments. No significant differences were observed between individuals with ESRD with and without frailty in age, sex, body mass index, or comorbidities. Frail individuals undergoing dialysis had significantly lower BMC at the third lumbar vertebra (L3) and femoral neck (FN); lower BMD and T-scores at L3, L4, and FN; and lower Z-scores at L4 and FN than those who were not frail and no significant differences in the biochemical parameters of MBD (Table 1). The severity of frailty (SFS scores) was negatively correlated with L3 (P = .04), L4 (P = .04), and FN BMD (P < .001). Frail individuals undergoing dialysis were more likely to have VCF (67% vs 24%, P = .04) and had more VCF segments (0.38 vs 1.33, P = .02) than those who were not frail. After adjusting for demographic characteristics and comorbidities, regression analyses showed that frailty was negatively associated with FN BMD (β = −4, t = −3.17, P = .004); higher SFS scores were also associated with higher risk of VCF (odds ratio (OR) = 1.8 per point; P = .01). Analyses including prefrail individuals yielded similar results. In line with the hypothesis, frailty in individuals with ESRD, similar to the general population, is significantly associated with lower lumbar spine and FN bone mass and decreases with greater severity of frailty. In addition to lower bone mass, these individuals had a greater likelihood of VCF and more VCF segments, which was significantly correlated with severity of frailty. It was recently reported that self-reported frailty is significantly associated with falls and fractures in individuals undergoing incident dialysis.8 That study focused exclusively on clinically significant episodes using administrative coding and risked missing silent events such as VCFs. Despite this difference, the greater risk (OR = 1.6) in that study is close to that of the current study (OR = 1.8), lending support to the current findings. DXA results can underestimate the risk of fracture in individuals with ESRD, which is partially related to failure to incorporate the influences of MBD (bone remodeling and microarchitectural deterioration).9 Measuring of novel bone turnover markers, such as procollagen type-1 N-terminal pro-peptide, has been recommended to enhance the utility of DXA, but such advanced assays are rarely available. Assessment of frailty, especially using self-report instruments, might serve as a useful surrogate to assist in predicting the risk of VCF in individuals with ESRD, because these questionnaires are easy to administer and do not require laboratory tests. As demonstrated above, self-reported frailty and its severity have independent associations with lumbar spine and FN bone mass, and more importantly, frailty is a significant predictor of VCF in these individuals. Incorporating frailty and its severity into fracture risk prediction might therefore aid in clinical decision-making for individuals with ESRD. We are grateful for the assistance in data collection from the staffs at National Taiwan University Hospital Jinshan Branch. Author Contributions: All authors had full access to the data of this study and accept responsibility for data integrity and accuracy. Chao: study design, enrollment of participants, data collection, analysis and interpretation, drafting the manuscript. Chan, Chiang, Huang: study design, data collection and analysis, drafting the manuscript. Sponsor's Role: None.
Other Subjects
aged; bone mass; bone mineral; clinical article; compression fracture; dialysis; end stage renal disease; femoral neck; frail elderly; human; Letter; lumbar vertebra; phenotype; spine fracture; vertebral compression fracture
Publisher
Blackwell Publishing Inc.
Type
letter