Outcomes after acute ischemic stroke in the United States: does residential ZIP code matter?

We sought to analyze the impact of socioeconomic status (SES) on in-hospital outcomes, cost of hospitalization, and resource use after acute ischemic stroke.

We used the 2003-2011 Nationwide Inpatient Sample database for this analysis. All admissions with a principal diagnosis of acute ischemic stroke were identified by using International Classification of Diseases, Ninth Revision codes. SES was assessed by using median household income of the residential ZIP code for each patient. Quartile 1 and quartile 4 reflect the lowest-income and highest-income SES quartile, respectively. During a 9-year period, 775,905 discharges with acute ischemic stroke were analyzed. There was a progressive increase in the incidence of reperfusion on the first admission day across the SES quartiles (P-trend<0.001). In addition, we observed a significant reduction in discharge to nursing facility, across the SES quartiles (P-trend<0.001). Although we did not observe a significant difference in in-hospital mortality across the SES quartiles in the overall cohort (P-trend=0.22), there was a significant trend toward reduced in-hospital mortality across the SES quartiles in younger patients (<75 years) (P-trend<0.001). The mean length of stay in the lowest-income quartile was 5.75 days, which was significantly higher compared with other SES quartiles. Furthermore, the mean adjusted cost of hospitalization among quartiles 2, 3, and 4, compared with quartile 1, was significantly higher by $621, $1238, and $2577, respectively. Compared with the lowest-income quartile, there was a significantly higher use of echocardiography, invasive angiography, and operative procedures, including carotid endarterectomy, in the highest-income quartile.

Patients from lower-income quartiles had decreased reperfusion on the first admission day, compared with patients from higher-income quartiles. The cost of hospitalization of patients from higher-income quartiles was significantly higher than that of patients from lowest-income quartiles, despite longer hospital stays in the latter group. This might be partially attributable to a lower use of key procedures among patients from lowest-income quartile.