Antiparkinson drug adherence and its association with health care utilization and economic outcomes in a Medicare Part D population

Abstract

Objectives: We examine the associations of adherence to antiparkinson drugs (APDs) with health care utilization and economic outcomes among patients with Parkinson's disease (PD).

Methods: By using 2006-2007 Medicare administrative data, we examined 7583 beneficiaries with PD who filled two or more APD prescriptions during 19 months (June 1, 2006, to December 31, 2007) in the Part D program. Two adherence measures--duration of therapy (DOT) and medication possession ratio (MPR)--were assessed. Negative binomial and gamma generalized linear models were used to estimate the rate ratios (RRs) of all-cause health care utilization and expenditures, respectively, conditional upon adherence, adjusting for survival risk, sample selection, and health-seeking behavior.

Results: Approximately one-fourth of patients with PD had low adherence (MPR < 0.80, 28.7%) or had a short DOT (≤ 400 days, 23.9%). Increasing adherence to APD therapy was associated with decreased health care utilization and expenditures. For example, compared with patients with low adherence, those with high adherence (MPR = 0.90-1.00) had significantly lower rates of hospitalization (RR = 0.86), emergency room visits (RR = 0.91), skilled nursing facility episodes (RR = 0.67), home health agency episodes (RR = 0.83), physician visits (RR = 0.93), as well as lower total health care expenditures (-$2242), measured over 19 months. Similarly, lower total expenditure (-$6308) was observed in patients with a long DOT versus those with a short DOT.

Conclusions: In this nationally representative sample, higher adherence to APDs and longer duration of use of APDs were associated with lower all-cause health care utilization and total health care expenditures. Our findings suggest the need for improving medication-taking behaviors among patients with PD to reduce the use of and expenditures for medical resources.

Keywords: Medicare; antiparkinson drug; expenditures; health care utilization; medication adherence.