Introduction: Although rates of depression are increased in patients with transient ischemic attack (TIA), the effect of depression on recurrent cerebrovascular events is uncertain. Therefore, we aimed to calculate the risk of subsequent stroke in patients with comorbid depression at the time of TIA.
Methods: We used all-payer claims data on all nonfederal acute care hospitalizations in New York, California, and Florida from 2005-2013. Our cohort comprised all patients hospitalized for TIA (ICD-9-CM 435.x). The predictor variable was a diagnosis of depression (ICD-9-CM 296.20-.25, 296.30-.35, 300.4, 311 in any diagnosis code position) during the index hospitalization for TIA. Kaplan-Meier survival statistics were used to calculate cumulative rates of our primary composite outcome of ischemic and hemorrhagic stroke (ICD-9-CM 431, 433.x1, 434.x1, or 436 without concomitant trauma or rehabilitation codes). Cox proportional hazard analysis was used to examine the association between depression and stroke.
Results: We identified a total of 1,817,842 TIA patients, among whom 223,311 (12.3%) were discharged from their index TIA visit with a comorbid depression diagnosis. Over a mean follow-up of 4.2 (+/- 2.1) years, 227,501 patients were diagnosed with subsequent stroke. The 1-year cumulative rate of stroke was 3.5% in both patients with depression (95% CI, 3.3-3.7%) and without depression (95% CI, 3.5-3.6%). The 5-year cumulative rate of stroke was 8.5% (95% CI, 8.2-8.9%) in those with depression compared to 8.9% (95% CI, 8.7-9.0%) in patients without depression at the time of their TIA diagnosis. After adjusting for demographics and vascular risk factors, depression was not associated with subsequent stroke (hazard ratio, 1.0; 95% CI, 1.0-1.1; p=0.7). To reduce any misclassification error, these results were unchanged in a sensitivity analysis which included only those patients who underwent brain magnetic resonance imaging during their index hospitalization for TIA.
Conclusions: A comorbid diagnosis of depression at the time of TIA is not associated with an increased risk of subsequent stroke. Future research should evaluate whether incident depression diagnosed after hospital discharge for TIA is associated with heightened stroke risk.