Browsing School, Graduate by Subject "Fractures, Bone"
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Cost and Management of Fractures in Medicare Beneficiaries with Non-Metastatic Prostate Cancer Treated with Androgen Deprivation TherapyBackground: Androgen deprivation therapy (ADT) in prostate cancer (PCa) is associated with increased fracture risk and costs. There is limited information regarding the use of guideline-recommended bone mineral density (BMD) testing and bisphosphonate therapy. This study examined patient-specific (e.g., comorbidity) and non-patient-specific (e.g., physician specialist visits) factors associated with BMD testing, bisphosphonate therapy, fracture risk, and costs. Methods: This retrospective cohort analysis used linked Surveillance, Epidemiology, and End Results & Medicare data on men aged 65+ with non-metastatic PCa and treated with ADT. Cox proportional hazards models examined the association between baseline Charlson Comorbidity Index (CCI) and fracture, accounting for death as a competing risk. Partitioned weighted least squares regression models quantified the 5-year incremental cost of fractures. Multivariable logistic regression models quantified the effect of specialist visits on BMD testing and bisphosphonate use. Results: Of 30,904 men, 6,779 (22%) had a fracture during 5-years of follow-up. Among men aged 66-74 years, the sub-hazard ratio (SHR) (95% CI) for fracture was 1.17 (1.05-1.29) for CCI=1 and 1.69 (1.51-1.90) for CCI=2+ (reference: CCI=0); CCI was not associated with fracture risk among the oldest men aged 85+ years. The mean (95% CI) incremental cost of fractures was $31,800 ($31,709-$31,891), $34,320 ($34,152-$34,488), and $46,678 ($46,534-$46,822) among patients with CCI=0, CCI=1, and CCI=2+, respectively. Following ADT initiation, 17.9% received BMD testing and 9.6% received bisphosphonate. Compared to men who saw a urologist and primary care physician, bisphosphonate receipt was more likely among men with a urologist and medical oncologist involved in their care (AOR=1.89; 95% CI=1.38-2.57), and less likely among men who saw a urologist and radiation oncologist (AOR=0.63; 95% CI=0.42-0.95). There were no statistically significant associations between specialist visits and BMD testing. Conclusions: Patients with greater comorbidity burden had increased fracture risk and higher costs associated with fractures. These patients could benefit from regular monitoring of BMD and bisphosphonate therapy, which occurred in approximately 2 in 10 men. Involving certain types of specialists (e.g., medical oncologists) in the management of men with PCa could be beneficial for bone health management.
Evaluating the Relationship between Muscle and Bone Modeling Response in Older AdultsBackground: Bone modeling, the process that continually adjusts bone strength in response to prevalent muscle-loading forces throughout an individual's lifespan, may play an important role in bone fragility with age. Femoral stress, an index of bone modeling response can be estimated using measurements of DXA derived bone geometry and loading information incorporated into an engineering model. Assuming that individuals have adapted to habitual muscle loading forces, greater stresses indicate a diminished response and a weaker bone Aims/Methods: The aims of this dissertation were to 1) evaluate the association of femoral stress with measures of lean mass and muscle strength among healthy older adults participating in the Health ABC study using linear regression; 2) determine whether femoral stress predicts incident fracture among the same cohort of older adults using cox proportional hazards models; and 3) evaluate the association of femoral stress with measures of lean mass and muscle strength in women after hip fracture participating in the 3rd and 4th cohort of the Baltimore Hip Studies using linear regression and to determine whether femoral stress changes the year following fracture using longitudinal data analysis. Results: Lean mass explained more of the variation in femoral stress than measures of muscle strength among healthy older men and women as well as in women with hip fracture. Remaining variability in femoral stress may reflect individual variation in modeling response. After adjusting for measures of lean mass and strength, women in the highest tertile of femoral stress had 77% higher hazard of fracture and men in the highest tertile of femoral stress had 84% higher hazard of fracture relative to women and men in the lowest tertile, respectively. This suggests that deficiencies in bone modeling response may be an important predictor of fracture. Femoral stress did not appear to change the year following fracture in older women. Conclusion: Future studies should focus on refining measures of bone modeling response by incorporating better measures of muscle force. While femoral stress does not have clinical applications per se, it allows us to investigate a potentially important mechanism underlying bone fragility and provides a framework for thinking about treatments that could improve the interaction between muscle and bone.