Predictors of first-year nonadherence and discontinuation of statins among older adults: a retrospective cohort study

Abstract

Aims: The aim of this study was to examine the level of and predictors of statin nonadherence and discontinuation among older adults. Methods: Among 22 340 Australians aged ≥65 years who initiated statin therapy from January 2014 to December 2015, we estimated the first-year nonadherence (proportion of days covered [PDC] <0.80) and discontinuation (≥90 days without statin coverage) rates. Predictors of nonadherence and discontinuation were examined via multivariable logistic regression. Analyses were performed separately for general beneficiaries (with a higher co-payment; n = 4841) and concessional beneficiaries (with a lower co-payment; n = 17 499). Results: During the one-year follow-up, 55.1% were nonadherent (concessional 52.6%; general beneficiaries 64.2%) and 44.7% discontinued statins (concessional 43.1%; general beneficiaries 50.4%). Among concessional beneficiaries, those aged 75–84 years and ≥85 years were more likely to discontinue than people aged 65–74 years (odds ratio 1.11, 95% confidence interval 1.04–1.19 and 1.38, 1.23–1.54, respectively). Diabetes was associated with an increased likelihood of nonadherence and discontinuation, while hypertension, angina and congestive heart failure were associated with a lower likelihood of nonadherence and discontinuation. Anxiety was associated with an increased likelihood of discontinuation, but polypharmacy (concurrent use of five or more drugs) was associated with a lower likelihood of nonadherence and discontinuation. Statin initiation by a general medical practitioner was associated with both increased likelihood of nonadherence and discontinuation. Similar predictors of nonadherence and discontinuation were identified for the general beneficiaries. Conclusions: Among older adults prescribed statins, first-year nonadherence and discontinuation are high. Specific population subgroups such as people aged ≥85 years, those with diabetes or anxiety may require additional attention to improve statin adherence.