Multimorbidity Increases Risk of Osteoporosis Under-Diagnosis and Under-Treatment in Patients at High Fracture Risk: 45 and up a Prospective Population Based-Study
Authors: Bliuc Dana , Tran Thach , Alarkawi Dunia , Chen Weiwen , Blank Robert D , Ensrud Kristine E , Blith Fiona , March Lyn , Center Jacqueline 
Published: May 2021

Abstract
Background: Management of osteoporosis following fracture is suboptimal. Multimorbidity adds to clinical management complexity in the elderly but its contribution to the osteoporosis treatment gap has never been investigated. Objectives: To determine the impact of multimorbidity on fracture risk and on osteoporosis investigation and treatment in patients at high fracture risk. Design and Setting: The 45 and Up Study is a prospective population-based cohort study in NSW, Australia with questionnaire data linked to hospital records by the Centre for Health Record Linkage (CHeReL) and the Pharmaceutical Benefits Scheme (PBS) and Medicare Benefits Scheme (MBS) data provided by Department of Human Services. Fractures identified from hospital records, comorbidities from questionnaires, hospital and PBS records. Bone mineral density (BMD) investigation obtained from MBS and treatment for osteoporosis from PBS. Participants: 16191 women and 9089 men with incident low-trauma fracture (2000 - 2017) classified in a high and low-risk group based on 10-year fracture risk threshold of 20% from the Garvan Fracture Risk Calculator (age, gender, prior fracture and falls). Main Outcome Measurements: Association of Charlson comorbidity index (CCI) with fracture. Likelihood of BMD investigation and treatment initiation. Outcomes ascertained by logistic regression and re-fracture risk by Cox models. Results: Individuals at high fracture risk were significantly older [women (mean age ±SD) 77 ± 10 vs 57 ±4 for high- vs low risk and men 86±5 vs 65±8 for high vs low risk] and had a higher morbidity burden [women, CCI ≥ 2 40% vs 12% for high- vs low-risk and men 53% vs 26% for high vs low risk]. Being in the high-risk group as well as a higher CCI were independently associated with &gt; 2-fold higher risk of re-fracture. However, in the high-risk group, only 28% (48% women and 17% men) had a BMD investigation and 31% (24% women and 14% men) received anti-osteoporosis medication post-fracture. A higher CCI was associated with a lower probability of both BMD investigation [CCI 2–3 vs 0–1, RR 0.73 (0.65–0.82) for women, and 0.50 (0.40–0.64) for men and CCI ≥4 vs 0–1, RR 0.50 (0.41- 0.62) for women and 0.36 (0.25–0.52) for men] and treatment initiation [CCI 2–3 vs 0–1, RR 0.88 (0.77–0.98) for women and 0.75 (0.60–0.95) for men and CCI ≥4 vs 0–1, RR 0.75 (0.59- 0.95) for women and 0.35 (0.23–0.53) for men]. Conclusion: Multimorbidity, despite being associated with the highest fracture risk, significantly lowers the likelihood of osteoporosis investigation and treatment. These findings suggest that fracture risk is either under-estimated or under-prioritized in the context of multimorbidity. Our findings highlight the need for improved delivery of fracture preventive care in this setting. More generally, they also point out the need for a better understanding of how problems are prioritized in complex clinical situations.