Session Information
Session Type: Abstract Submissions (ACR)
Risk Factors for Prevalent and Progressive Bone Deficits Among Adult Men and Women with Cystic Fibrosis
Background/Purpose
Cystic Fibrosis (CF) is associated with an increased risk of osteoporosis and incident fracture. Factors associated with prevalent and progressive bone deficits in adults with CF have not been comprehensively studied. This study assessed the independent predictors of baseline bone mineral density (BMD) and 2-year changes BMD in adults with CF.
Methods
Sixty-four adult patients with CF, ages 18-57, were recruited from the Massachusetts General Hospital Cystic Fibrosis Care Center. Dual energy absorptometry (DXA) was performed at the spine and radius at baseline and 2-years. Estimates of fat-free mass index (FFMI) and fat mass index (FMI) were determined using height, weight, and tetrapolar bioelectric impedance analysis. All subjects underwent lung spirometry within 1 month of the study visit to measure forced vital capacity (FVC) and forced expiratory volume (FEV1). Linear regression models evaluated predictors of baseline BMD Z-scores and change in anterior-posterior (AP) spine BMD Z-score over the 2-year follow-up. Osteopenia was defined as a BMD Z-score of ²-1.0.
Results
Osteopenia was present in 52% of subjects. Compared to patients without osteopenia, subjects with osteopenia were more likely to be male (67% v. 32%, p=0.009), more likely to be current users of glucocorticoids (21% v. 0%, p<0.001), had lower percent body fat (19% v. 23%, p=0.04), and were more likely to have had a previous fracture (60% v. 46%, p=0.007). In multivariable models, greater estimated FFMI and greater height, but not greater FMI, were associated with greater BMD after adjusting for sex (Table 1). Low FVC and greater adiposity were associated with greater loss of BMD at the A/P spine over two years (p<0.05) (Table 2).
Conclusion
Male sex, short stature, and low lean mass at baseline are associated with low BMD among adults with CF. Greater adiposity and lower lung function in women are predictors of negative change in BMD Z-score at the A/P spine at 2-years of follow-up.
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Table 1:Multivariable associations between baseline body composition factors and baseline bone density Z-score at different measurement locations. |
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β (95% CI) |
p-value |
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DXA AP Spine (n=54)*
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Height (cm)
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0.073 (-0.014, 0.13) |
0.02 |
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eFFMI (kg/m2)
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0.19 (-0.019, 0.39) |
0.07 |
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eFMI (kg/m2)
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-0.072 (-0.25, 0.11) |
0.4 |
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DXA Radius (n=20)*
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Height (cm)
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0.12 (0.045, 0.20) |
0.004 |
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eFFMI (kg/m2)
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0.34 (0.11, 0.56) |
0.006 |
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eFMI (kg/m2)
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-0.11 (-0.19, -0.035) |
0.2 |
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*Also adjusted for sex. DXA: Dual Electron Absorptometry; eFFMI: Estimated Fat-Free Mass Index; eFMI: Estimated Fat Mass Index
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Table 2: Univariate associations between baseline factors and change in BMD Z-score over 2-years (N=39). Body composition variables adjusted for sex*.
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ÆDXA A/P Spine Z
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β (95%CI) |
p-value |
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Male Sex
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0.0065 (-0.28, -0.29)
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1 |
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BMI*
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-0.015 (-0.061, 0.030) |
0.5 |
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% Fat*
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-0.019 (-0.036, -0.00075) |
0.04 |
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eFFMI*
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0.0041 (-0.078, 0.086)
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0.9 |
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eFMI*
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-0.059 (-0.11, -0.0048) |
0.03 |
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FVC
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0.0065 (0.0015, 0.013)
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0.05 |
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FEV1
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0.0051 (-0.00056, 0.011)
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0.08 |
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Prednisone Use
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0.12 (-0.16, 0.40)
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0.4 |
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Baseline Z-Score
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-0.033 (-0.13, -0.068) |
0.5 |
Disclosure:
J. Baker,
None;
P. Melissa,
None;
K. Herlyn,
None;
A. S. Pizzo,
None;
A. Lapey,
None;
J. Finklestein,
None;
P. A. Merkel,
Genentech and Biogen IDEC Inc.,
2,
Bristol-Myers Squibb,
2,
GlaxoSmithKline,
2,
Actelion Pharmaceuticals US,
2,
Actelion Pharmaceuticals US,
5,
Sanofi-Aventis Pharmaceutical,
5,
Chemocentryx,
5.
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