Medication Adherence in Community-dwelling Older People Exposed to Chronic Polypharmacy

Background: To evaluate medication adherence and associated factors of seven of the most common drug classes prescribed to community-dwelling older people.

Methods: This is a retrospective cohort study on medication adherence in community-dwelling older people (65-94 years old) on chronic polypharmacy and recorded from 2013 to 2015 in the administrative database of the Lombardy region (Northern Italy). Adherence was assessed for diabetic drugs, antithrombotic agents, drugs acting on the renin-angiotensin system, statins, bisphosphonates, antidepressants and drugs for obstructive airway diseases by calculating the medication possession ratio (MPR). Patients were then divided in fully (MPR ≥80%), partially (40%≤MPR<80%) and poorly adherent (10%<MPR<40%).

Results: Among 140 537 patients included in the study, only 19.3% was fully adherent to all the therapies considered. Almost 40% of them were poorly adherent to at least one drug class, becoming 50% when patients exposed to four or more drug classes were considered. In adjusted regression model, being women (OR=1.14, 95% CI 1.13 to 1.16) and aged ≥80 years old (OR=1.22, 95% CI 1.20 to 1.24) were associated with an overall lower adherence. Instead, the participation to an experimental healthcare programme was associated with higher adherence (OR=0.92, 95% CI 0.87 to 0.96). Furthermore, being coprescribed with ≥10 drugs was associated with lower adherence to all the drug classes, with different effects (ORs from 0.42 to 0.73).

Conclusion: This study overall shows a low medication adherence in community-dwelling older people on chronic polypharmacy, especially in women and oldest old. The implementation and promotion of healthcare programmes for these patients could help improve overall adherence to chronic drug therapies.