Association of Socioeconomic Status With Ischemic Stroke Survival

Rosa Maria Vivanco-Hidalgo, MD, PhD, MPH; Aida Ribera, PhD; Sònia Abilleira, MD, PhD

Disclosures

Stroke. 2019;50(12):3400-3407. 

In This Article

Abstract and Introduction

Abstract

Background and Purpose: The aim of the study was to determine the impact of individuals' socioeconomic status and their Primary Care Service Area Socioeconomic Index on survival after ischemic stroke.

Methods: We conducted a nationwide population-based cohort study in Catalonia, Spain. We included all patients with first ischemic stroke admitted to a public hospital between January 1, 2015, and December 31, 2016. We measured both individual socioeconomic status (categorized as exempts, <€18 000 [$US 20 468] income per year, and >€18 000 income per year) and Primary Care Service Area Socioeconomic Index (from 0 to 100 categorized in quartiles).We used mixed-effects logistic and survival models to estimate odds ratios and hazard ratios for the short- (30 days) and the long-term (3 years) all-cause case fatality rates by individuals' socioeconomic status groups.

Results: The cohort consisted of 16 344 ischemic stroke patients with 24 638 person-years of follow-up. We did not find an association between the lowest socioeconomic individual status and short-term survival (odds ratio, 1.03; 95% CI, 0.76–1.40), although we found it in patients with <€18 000 income/year (odds ratio, 1.26; 95% CI, 1.10–1.45). At long-term, after adjustment, we observed a gradient in mortality risk with decreasing individual socioeconomic status (hazard ratio, 1.52; 95% CI, 1.30–1.77). The Primary Care Service Area Socioeconomic Index had only an influence on short-term survival (odds ratio, 1.19; 95% CI, 1.03–1.37).

Conclusions: Individuals' socioeconomic status was associated with short- and long-term survival in patients with ischemic stroke. Conversely, Primary Care Service Area Socioeconomic Index measures had an influence only in short-term survival. A small fraction of this association is due to differences in comorbidity and cardiovascular risk factors. Interventions addressing both individuals' and primary care service socioeconomic aspects might eventually affect differently short- and long-term survival.

Introduction

Stroke is the second leading cause of death worldwide. Although in the last 2 decades, mortality rates have decreased in both high-income and low/middle-income countries, absolute number of related deaths are increasing, mainly because of the expanding and aging population.[1]

The latest evidence shows that there are socioeconomic disparities in survival after stroke[2–4] both in high-income and low/middle-income countries. However, there are still several areas of uncertainty on that association that should be addressed. Mortality studies have focused mainly on short-term outcomes, and the relation between socioeconomic status and long-term survival is scarce and still inconclusive.[2] The majority of studies used either individual factors (such as income, occupation, or social class) or neighborhood deprivation index as measures of patients' socioeconomic status. Conversely, few studies have tested the multilevel aspects of socioeconomic status in a single model to assess the influence of each aspect in survival, showing heterogeneous results.[5] This aspect is crucial, as potential interventions to improve survival in stroke might depend on the mechanisms (or mediators) of the association between socioeconomic status (at different levels) and health.[6] On the contrary, possible explanations for the association between socioeconomic status and worse prognosis point to conventional cardiovascular risk factors,[7] although they would not fully explain the underlying mechanisms.

To overcome the limitations of the previous studies, we performed a nationwide population-based cohort study of patients with ischemic stroke admitted to public hospitals in Catalonia in 2015 to 2016 to compare both short- and long-term survival across different individual socioeconomic categories and tested the influence of comorbidities, cardiovascular risk factors, and the Primary Care Service Area Socioeconomic Index (PCSA index; deprivation index).

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