11 August, 2014
Chronic pharmacologic treatments have the risk of low adherence and persistence which depend on the disease severity, preventive objectives, co-morbidity, other concurrent medications (polymedication) and adverse events. Wade and colleagues  reported follow-up data regarding osteoporosis medication persistence and switching at 24 months and 36 months in postmenopausal women from the cohort of the US Prospective Observational Scientific Study Investigating Bone Loss Experience (POSSIBLE). Postmenopausal women (n = 3011) were enrolled by 134 primary-care physicians who were considered to be the top 40% prescribers of osteoporosis medications in 2003. Medications initially prescribed were oral bisphosphonates (alendronate, risedronate, or ibandronate), oral or transdermal postmenopausal estrogen (PME), parathyroid hormone, calcitonin, raloxifene, or a non-prescription agent (calcium and/or vitamin D supplement).
At baseline, bone mineral density (BMD) corresponded in 50% to osteopenia, in 44% to osteoporosis, and the remaining 6% did not have a densitometry measurement or had another diagnosis. Mean body mass index and age for the entire population were 26.5 kg/m2 (95% confidence interval 26.3–26.7) and 64.6 years, respectively. Twenty-three percent had a history of fractures since the age of 45 years and 9% were current smokers. Patients completed questionnaires at baseline and at semi-annual intervals regarding sociodemographic and lifestyle characteristics, the osteoporosis medications they used, the European osteoporosis-specific health-related quality of life (EuroQoL EQ-5D) and the short version of the Osteoporosis Assessment Questionnaire. Physician-relevant medical data were updated at routine visits during the 3 years of follow-up. Persistence of treatment at 24-month follow-up was 46.2% and at 36 months 36.8%. Women who initiated with a bisphosphonate and then switched during follow-up persisted using the same type of medication. Women who switched from a non-bisphosphonate treatment (including PME) were most likely to switch to a bisphosphonate. In addition, those who used PME at study entry were more likely to completely discontinue therapy both at the 24- and 36-month follow-up.
Predictors of non-persistence in newly initiating therapy or switching to a new treatment were side-effects, low quality of life, smoking and site of residency. Forty-two percent of participants had at least 24 months of treatment persistence and 28% persisted under treatment at the 36 months of follow-up.
The purpose of osteoporosis treatment is to reduce the incidence of low-intensity fractures. The study of Wade and colleagues  is devoted to assess the long-term persistence and switching patterns of postmenopausal women using osteoporosis therapies in the US POSSIBLE cohort. Tosteson and colleagues  have previously described the initial follow-up results at 1 year. The studied sample included a heterogeneous group of postmenopausal women with osteopenia, osteoporosis, and/or a history of fractures since the age of 45 years recruited by a large number of US primary-care physicians who were among the top prescribers of osteoporosis treatments. Indications for the use of the studied medications would reflect the North American clinical practice as compared to other countries, cultures and/or sociodemographic factors . The most common initial medications prescribed were bisphosphonates (73%), followed by raloxifene (12%) and PME (11%), percentages which remained at the 36-month follow up. Percentages of women under the initial treatment group persisted in the 24- and 36-month follow-ups for all studied therapeutic options. Bisphosphonate users remained in the same treatment group, although a proportion of women using monthly dosing at the initial treatment moved to either a daily or a weekly dosing administration, suggesting that convenience of administration is not the sole value of a chronic treatment election. Other factors were also relevant, including side-effects, medication cost, perceived efficacy, socio-economic factors, physicians' information, and unknown factors. It is interesting that women treated with hormone therapy discontinued therapy and did not switch to another type of treatment.
It seems that rates of compliance and persistence to osteoporosis treatment are very important to prevent fractures , and compliance may be a better predictor of fracture risk than medication persistence . A significant positive association exists between poor adherence and increased risk of osteoporotic fractures, which becomes augmented with longer treatment duration. Poor adherence to treatment increases the risk of osteoporotic fractures in subject with long-term treatment . The results from Wade and colleagues  reinforce this issue, although the authors did not include fracture results in the US POSSIBLE cohort. Furthermore, studied women and selected physicians in the US POSSIBLE cohort are not necessarily representative of all patients and medical practices. In fact, therapy persistence and switching of osteoporosis medication were influenced by place of residency within the US and hence patients included in the study are not necessarily representative of the entire population of subjects being treated for osteoporosis. In the POSSIBLE cohort of the European Union, almost 40% of patients received osteoporosis treatment due to a previous fracture while 25% of patients did not have a previous fracture or BMD measurement, suggesting that medications were indicated due to other risk factors .
The efficacy of anti-fracture drugs for osteoporosis depends on safety and tolerability, convenience of treatment compliance and persistence in the treatment, adverse effects and cost. It cannot be omitted that compliance to treatment also depends on the patient's expected benefits, existing co-morbidity and the patient's priorities or wishes to treat some conditions or diseases and delays to prevent others. It is possible that novel anti-osteoporotic agents, such as denosumab or systemic bisphosphonates, may improve treatment compliance and persistence [8,9] as compared to the analyzed treatments reported by Wade and colleagues . In addition, it seems that the new, long-acting, anti-osteoporotic compounds may still provide protection against fragile fractures even after treatment interruption .
Further studies regarding compliance and treatment persistence are warranted among postmenopausal women with osteoporosis and risk fractures that include the analysis of various other factors such as countries and cultures, perceptions and desires of women about pharmacologic osteoporosis management in the reduction of fragility fracture risk.
Faustino R. Pérez-López
Professor of Obstetrics & Gynecology, University of Zaragoza Faculty of Medicine and Lozano Blesa University Hospital, Zaragoza, Spain
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