Hip fractures in users of first- vs. second-generation bisphosphonates

Comparison of orally administered bisphosphonate drugs in reducing the risk of hip fracture in older adults: a population-based cohort study

BACKGROUND

Orally administered bisphosphonate drugs (i.e., alendronate, etidronate, risedronate) can reduce the risk of vertebral fracture. However, only alendronate and risedronate have proven efficacy in reducing the risk of hip fracture. We sought to examine the comparative effectiveness of orally administered bisphosphonate drugs in reducing hip fractures among older adults.

METHODS

We identified new users of orally administered bisphosphonate drugs in British Columbia and Ontario between 2001 and 2008. We used province- and sex-specific propensity score-matching strategies to maximize comparability between exposure groups. We used Cox proportional hazards models to compare time-to-hip fracture within 1 year of treatment between exposures by sex in each province. Our secondary analyses considered hip fracture rates within 2 and 3 years' follow-up. We used alendronate as the reference for all comparisons and pooled provincial estimates using random effects variance-weighted meta-analysis.

RESULTS

We identified 321 755 patients who were eligible for inclusion in the study. We found little difference in fracture rates between men (pooled hazard ratio [HR] 0.94, 95% confidence interval [CI] 0.74-1.14) or women (pooled HR 1.15, 95% CI 0.73-1.56) taking risedronate and those taking alendronate. We similarly identified little difference in fracture rates between women taking etidronate and those taking alendronate (pooled HR 1.00, 95% CI 0.82-1.18). However, we identified lower rates of hip fracture among men taking etidronate relative to alendronate (pooled HR 0.77, 95% CI 0.60-0.94). Results extended to 2 and 3 years' follow-up were similar. However, with 3 years' follow-up, rates of hip fracture were lower among women in British Columbia who had taken alendronate.

INTERPRETATION

We identified little overall difference between alendronate and risedronate in reducing the risk of hip fracture in men or women. Our finding that etidronate is associated with lower fracture risk among men is likely due to selection bias. The long-term comparative effects of orally administered bisphosphonate drugs warrant further study.

Osteoporosis medication prescribing in British Columbia and Ontario: impact of public drug coverage

We compared the patterns of osteoporosis medication prescribing between two provinces in Canada with different public drug coverage policies. Oral bisphosphonates were the primary drugs used, yet access to the second-generation oral bisphosphonates (alendronate, risedronate) was limited in one region. Implications of differential access to oral bisphosphonates warrants further study.

INTRODUCTION

Approved therapies for treating osteoporosis in Canada include bisphosphonates, calcitonin, denosumab, raloxifene, and teriparatide. However, significant variation in access to these medications through public drug coverage exists across Canada. We sought to compare patterns of osteoporosis medication prescribing between British Columbia (BC) and Ontario.

METHODS

Using dispensing data from BC (PharmaNet) and Ontario (Ontario Drug Benefits), we identified all new users of osteoporosis medications aged 66 or more years from 1995/1996 to 2008/2009. We summarized the number of new users by fiscal year, sex, and index drug for each province. BC data were also stratified by whether drugs were dispensed within or outside public PharmaCare.

RESULTS

We identified 578,254 (n = 122,653 BC) eligible new users. Overall patterns were similar between provinces: (1) most patients received an oral bisphosphonate (93% in BC and 99% in Ontario); (2) etidronate prescribing declined after 2001/2002, reaching a low of 41% in BC and 10% in Ontario in 2008/2009; and (3) the proportion of males treated increased over time, from 7% in 1996/1997 to 25% in 2008/2009. However, we note major differences within versus outside the BC PharmaCare system. In particular, <2% of drugs dispensed within PharmaCare compared to 79% of drugs dispensed outside PharmaCare were for a second-generation bisphosphonate (alendronate or risedronate).

CONCLUSIONS

Oral bisphosphonates are the primary drugs used to treat osteoporosis in Canada. Prescribing practices changed over time as newer medications came to market, yet access to second-generation bisphosphonates through BC PharmaCare was limited. Implications of differential access to oral bisphosphonates warrants further study.

Levothyroxine dose and risk of fractures in older adults: nested case-control study

OBJECTIVE

To quantify the effect of levothyroxine dose on risk of fractures in older adults.

DESIGN

Nested case-control study.

SETTING

Population based health databases, Ontario, Canada.

PARTICIPANTS

Adults aged 70 or more prescribed levothyroxine between 1 April 2002 and 31 March 2007 and followed for fractures until 31 March 2008. Cases were cohort members admitted to hospital for any fracture, matched with up to five controls from within the cohort who had not yet had a fracture.

MAIN OUTCOME MEASURE

Primary outcome was fracture (wrist or forearm, shoulder or upper arm, thoracic spine, lumbar spine and pelvis, hip or femur, or lower leg or ankle) in relation to levothyroxine use (current, recent past, remote). Risk among current users was compared between those prescribed high, medium, and low cumulative levothyroxine doses in the year before fracture.

RESULTS

Of 213,511 prevalent levothyroxine users identified, 22,236 (10.4%) experienced a fracture over a mean 3.8 years of follow-up, 18,108 (88%) of whom were women. Compared with remote levothyroxine use, current use was associated with a significantly higher risk of fracture (adjusted odds ratio 1.88, 95% confidence interval 1.71 to 2.05), despite adjustment for numerous risk factors. Among current users, high and medium cumulative doses (>0.093 mg/day and 0.044-0.093 mg/day) were associated with a significantly increased risk of fracture compared with low cumulative doses (<0.044 mg/day): 3.45 (3.27 to 3.65) and 2.62 (2.50 to 2.76), respectively.

CONCLUSION

Among adults aged 70 or more, current levothyroxine treatment was associated with a significantly increased risk of fracture, with a strong dose-response relation. Ongoing monitoring of levothyroxine dose is important to avoid overtreatment in this population.

Which fractures are most attributable to osteoporosis?

BACKGROUND

Determining anatomic sites and circumstances under which a fracture may be a consequence of osteoporosis is a topic of ongoing debate and controversy that is important to both clinicians and researchers.

METHODS

We conducted a systematic literature review and generated an evidence report on fracture risk based on specific anatomic bone sites and fracture diagnosis codes. Using the Research and Development/University of California at Los Angeles appropriateness process, we convened a multidisciplinary panel of 11 experts who rated fractures according to their likelihood of being because of osteoporosis based on the evidence report. Fracture sites (as determined by International Classification of Diseases Clinical Modification codes) were stratified by four clinical risk factor categories based on age, sex, race/ethnicity (African American and Caucasian), and presence or absence of trauma.

RESULTS

Consistent with current clinical experience, the fractures rated most likely because of osteoporosis were the femoral neck, pathologic fractures of the vertebrae, and lumbar and thoracic vertebral fractures. The fractures rated least likely because of osteoporosis were open proximal humerus fractures, skull, and facial bones. The expert panel rated open fractures of the arm (except proximal humerus) and fractures of the tibia/fibula, patella, ribs, and sacrum as being highly likely because of osteoporosis in older Caucasian women but a lower likelihood in younger African American men.

CONCLUSION

Osteoporosis attribution scores for all fracture sites were determined by a multidisciplinary expert panel to provide an evidence-based continuum of the likelihood of a fracture being associated with osteoporosis.