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

Abstract

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

Methods and results: 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.

Conclusions: 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.

Keywords: ZIP code; acute ischemic stroke; cost of illness; mortality; socioeconomic status.

Figure 1.

Percent incidence and adjusted odds ratio for in‐hospital mortality, timely reperfusion, and need for discharge to long‐term acute care or subacute nursing or extended care facilities, stratified by ZIP code–based socioeconomic quartiles. All quartiles were based on median household income of the respective ZIP code. All comparisons were drawn with reference to the lowest quartile. Quartile 1, $1 to $37 999; quartile 2, $38 000 to $47 999; quartile 3, $48 000 to $62 999; quartile 4, ≥$63 000. ECF indicates extended care facility; LTAC, long‐term acute care; OR, odds ratio; SNF, subacute nursing facility.

Figure 2.

Percent incidence and adjusted odds ratio for in‐hospital death, timely reperfusion, and need for discharge to long‐term acute care or subacute nursing or extended care facilities, stratified by ZIP code–based socioeconomic quartiles after eliminating all patients who were transferred from an outside healthcare facility. All quartiles were based on median household income of the respective ZIP code. All comparisons were drawn with reference to the lowest quartile. Quartile 1, $1 to $37 999; quartile 2, $38 000 to $47 999; quartile 3, $48 000 to $62 999; quartile 4, ≥$63 000. ECF indicates extended care facility; LTAC, long‐term acute care; OR, odds ratio; SNF, subacute nursing facility.

Figure 3.

Trends demonstrating the incidence of study outcomes across the 4 socioeconomic quartiles across the entire study duration (2003–2011). A, Trend of in‐hospital mortality. B, Trend of timely reperfusion. C, Trend of discharge to long‐term acute care/subacute nursing/extended care facility. D, Trend of the cost of hospitalization. Quartile 1, $1 to $38 999; quartile 2, $39 000 to $47 999; quartile 3, $48 000 to $63 000; quartile 4, ≥$63 000.