Longitudinal Medication Adherence in Older Adults With Multimorbidity and Association With Health Care Utilization: Results From the Irish Longitudinal Study on Ageing.

BACKGROUND

The association between objectively measured nonadherence and health care utilization in multimorbid older people is unclear.

OBJECTIVE

To measure medication adherence across multiple chronic conditions, identify adherence patterns, and estimate the association between adherence and self-reported health care utilization.

METHODS

This is a retrospective cohort study of multimorbid participants aged ≥70 years in the Irish LongituDinal Study on Ageing (TILDA). Eligible participants had linked pharmacy claims data and completed TILDA wave 2 (2 years after wave 1). The RxRisk-V tool was used to identify multimorbidity. Average adherence (AA) across RxRisk-V conditions was estimated using the CMA7 function (AdhereR). Group-based trajectory models (GBTMs) identified adherence patterns in the 12 months following wave 1. Negative binomial regression was used to estimate the association between adherence and the rate of subsequent self-reported general practitioner [GP] visits, emergency department (ED) visits, outpatient visits, and hospitalizations in the 12 months following adherence measurement (reported at wave 2). Adjusted Incident Rate Ratios (aIRR) and 95% CIs are presented.

RESULTS

Higher AA (CMA7) was associated with a small significant decrease in GP visit rate (aIRR = 0.70; CI = 0.53-0.94) and outpatient visit rate (aIRR = 0.44; CI = 0.23-0.81). GBTM identified 6 adherence groups (n = 1050). Compared with high adherers, group 1 (rapid decline, modest increase) membership (aIRR = 1.72; CI = 1.09-2.73) and group 4 (high adherence, delayed decline) membership (aIRR = 1.92; CI = 1.19-3.05) significantly increased ED visit rate.

CONCLUSION AND RELEVANCE

Suboptimal medication adherence in multimorbid older adults is associated with increased health care utilization. Identification of suboptimal adherence groups for medication management interventions may help decrease the health system burden and health care costs.