SHORT COMMUNICATIONMortality in patients with schizophrenia admitted for incident ischemic stroke: A population-based cohort study
Introduction
People with schizophrenia experience markedly elevated risk of premature mortality (Hjorthøj et al., 2017; Oakley, et al., 2018). Evidence indicates that the vast majority of excess deaths in schizophrenia are attributable to physical diseases (Walker et al., 2015). Cardiovascular diseases (CVD), including stroke and ischemic heart disease (IHD), are a major contributor to premature mortality in schizophrenia. Recent meta-analytic reviews further show that schizophrenia is associated with increased incidence of stroke and IHD (Correll et al., 2017; Li et al., 2014).
In fact, a substantial body of literature demonstrates raised mortality after acute coronary syndrome among schizophrenia patients relative to the general population (Shao et al., 2020). Conversely, the relationship between schizophrenia and post-stroke mortality risk is understudied. Until now, there are only four published reports in this respect. One of these studies examined 5-year post-stroke mortality and reported that schizophrenia patients exhibited heightened mortality compared with non-schizophrenia controls (Tsai et al., 2012). The remaining three studies focused on short-term post-stroke mortality with mixed findings being observed (Kang et al., 2011; Kisley et al., 2009; Willers et al., 2018). Among those two studies investigating both 1-month and 1-year mortality after stroke, one revealed that schizophrenia was associated with increased 1-year mortality (Kisley et al., 2009), while the other failed to find any significant differences in mortality rates between patients with and without psychotic disorders (Willers et al., 2018). Another study even observed that schizophrenia patients had lower 90-day post-stroke mortality rate than those without schizophrenia (Kang et al., 2011). Of note, half of these reports comprised patients presenting with incident stroke and those with previous stroke history which may confound the study results (Kang et al., 2011; Willers et al., 2018). Additionally, most studies treated stroke as a single disease category without taking into consideration its subtypes in mortality analysis. Only one prior study assessed mortality rate specifically following ischemic stroke (Willers et al., 2018), which accounts for over 85% of acute strokes (Hankey, 2017), in schizophrenia.
To this end, we conducted a retrospective population-based cohort study with an aim to examine short-term (30-day and 1-year) mortality rates after admission for incident ischemic stroke in schizophrenia patients compared with those without psychotic disorders in Hong Kong (HK). Clinical data of the current investigation was retrieved from a territory-wide electronic medical record database of public healthcare services which provide government-subsidized, universal health coverage to 7.5 million HK residents. The potential confounding effects of medical comorbidities including hypertension, diabetes, hyperlipidemia, alcohol and substance use disorders on mortality outcome were adjusted to enable a better estimation of the relationship between schizophrenia and short-term mortality risk after stroke.
Section snippets
Data source
This study was conducted using Clinical Data Analysis and Reporting System (CDARS; Cheung et al., 2007), a territory-wide electronic health record database developed by the Hospital Authority (HA) which provides public healthcare services to HK residents by managing all public hospitals, specialist and general outpatient clinics in HK. Detailed description of CDARS has been reported elsewhere (Cheung et al., 2007). Briefly, CDARS is an integrated, longitudinal patient electronic record system
Results
Demographics and baseline characteristics of the study cohort (schizophrenia group, N = 817; control group, N = 8170) are summarized in Table 1. Schizophrenia patients had higher prevalence of hypertension, diabetes, alcohol and substance use disorders, but lower rate of hyperlipidemia than controls.
As shown in Table 2, schizophrenia patients exhibited significantly higher 1-year mortality rate than controls (16.9% vs 12.1%). The association between schizophrenia and 30-day mortality also
Discussion
The current study sought to investigate the short-term mortality after admission for incident ischemic stroke in schizophrenia patients relative to those without psychotic disorders. Our results showed that schizophrenia was associated with increased 1-year and 30-day post-stroke mortality risk (albeit approaching significance in the latter) after adjusting for medical comorbidities. This is thus consistent with the only previous study which also examined short-term mortality among patients
CRediT authorship contribution statement
Nicholas Chak Lam Yung: Data curation, Writing - original draft, Writing - review & editing, Funding acquisition. Corine Sau Man Wong: Conceptualization, Writing - review & editing. Joe Kwun Nam Chan: Writing - review & editing. Philip Chi Fai Or: Writing - review & editing. Eric Yu Hai Chen: Writing - review & editing. Wing Chung Chang: Conceptualization, Funding acquisition, Data curation, Writing - review & editing.
Role of funding source
The study was supported by the funding from the State Key Laboratory of Brain & Cognitive Sciences and the Master Research in Medicine Programme, University of Hong Kong.
Conflict of interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
Acknowledgment
The authors would like to thank the colleagues in Hospital Authority for their kind assistance in data retrieval for the current investigation.
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