Assessment of geriatric predictors of adherence to Zoledronic acid treatment for osteoporosis: a prospective follow-up study.

Objectives Discontinuation of bisphosphonate treatment remains high even with the long acting parenteral options. Whether there are some unidentified causes of noncompliance more specific to aged individuals is unknown. The aim of this study was to investigate baseline predictors of adherence to Zoledronic acid (ZOL) infusions among non-demented older adults with osteoporosis. Methods Patients aged ≥ 65 years who received a first ever ZOL infusion for osteoporosis were prospectively enrolled. Risk factors for osteoporosis and fractures, comorbidities, geriatric assessment measures, including depression, and anticholinergic burden were determined at baseline. Adherence was defined as taking the next ZOL infusion at 12 months. Results A total of 187 participants were included (mean age: 75.7 ± 6.3 years, female: 77.5%). Adherence to the next ZOL infusion was 66.8% (n = 125). Non-adherent participants (n = 62, 33.2%) had significantly higher frequency of historical height decrease and depression at baseline. Poor adherence was associated with height decrease, presence of depression, and higher anticholinergic burden in univariate analysis. After adjustment for relevant confounders, fragility fracture history (OR: 0.38, 95%CI: 0.17-0.86, p = 0.020), depression (OR: 0.32, 95%CI: 0.12-0.82, p = 0.018), and higher anticholinergic burden (OR: 0.67, 95%CI: 0.49-0.93, p = 0.017) were the predictors of lower adherence to ZOL infusion. Conclusions The rate of adherence to the next ZOL infusion was still suboptimal among older women and men in this study. Past osteoporotic fractures, depression, and higher anticholinergic drug burden predicted poor ZOL adherence. It was a novel finding that drug-related anticholinergic side effects adversely influenced adherence to another medication without anticholinergic properties.