Suboptimal medication possession ratio is associated with recurrent ischemic stroke in a veteran population

Recurrent stroke results in higher disability and mortality but might be mitigated through interventions that improve medication adherence. The medication possession ratio (MPR) is an objective proxy for adherence that may provide an individualized risk assessment for recurrent stroke.

This is a retrospective, longitudinal cohort study of patients with recent ischemic stroke or TIA referred to a Veterans Affairs vascular neurology outpatient clinic between 2010 and 2016. We calculated average MPR quartile for four medication classes used for secondary stroke prevention by reviewing pharmacy and medical records following an incident cerebral ischemic event. Traditional stroke risk factors were quantified using the Framingham Stroke Risk Profile (FSRP) score. We hypothesized that lower average MPR would relate to higher recurrent stroke risk more than FSRP or stroke etiological classification.

For 255 patients with stroke or TIA, 57 (22.4 %) patients had recurrent stroke during a median follow-up period of 5.0 years (IQR 2.0). Compared to optimal average MPR, each quartile lower average MPR was associated with higher cumulative incidence of recurrent stroke (subhazard ratio 1.63, 95 %CI: 1.24 to 2.14, p<0.001) while accounting for the competing risk of death and covarying for FSRP. Neither FSRP nor stroke etiology were associated with recurrent stroke. However, higher baseline systolic blood pressure starting at 132 mm Hg was independently associated with stroke recurrence.

MPR is an effective proxy measurement to assess risk of recurrent stroke. Systems-based and individualized interventions to improve medication adherence are needed to reduce recurrent stroke rates in VA populations.