Improving efficiency of stroke research: the Brain Attack Surveillance in Corpus Christi study

Prevalence of pre-stroke sleep apnea risk and short or long sleep duration in a bi-ethnic stroke population

BACKGROUND

The ethnic disparity in ischemic stroke between Mexican Americans (MAs) and non-Hispanic whites (NHWs) may be partly attributable to disparities in sleep and its disorders. We therefore assessed whether pre-stroke sleep apnea symptoms (SA risk) and pre-stroke sleep duration differed between MAs and NHWs.

METHODS

MA and NHW ischemic stroke survivors in the Brain Attack Surveillance in Corpus Christi (BASIC) project reported sleep duration and SA symptoms on the validated Berlin questionnaire, both with respect to their pre-stroke baseline. Log binomial and linear regression models were used to test the unadjusted and adjusted (demographics and vascular risk factors) associations of high-risk Berlin scores and sleep duration with ethnicity.

RESULTS

Among 862 subjects, 549 (63.7%) were MA and 514 (59.6%) had a high risk of pre-stroke SA. The MA and NHW subjects showed no ethnic difference, after adjustment for potential confounders, in pre-stroke SA risk (risk ratio (95% confidence interval (CI)): 1.06 (0.93, 1.20)) or in pre-stroke sleep duration (on average MAs slept 2.0 fewer minutes than NHWs, 95% CI: -18.8, 14.9 min).

CONCLUSIONS

Pre-stroke SA symptoms are highly prevalent, but ethnic differences in SA risk and sleep duration appear unlikely to explain ethnic stroke disparities.

Brainstem infarction and sleep-disordered breathing in the BASIC sleep apnea study

BACKGROUND

Association between cerebral infarction site and poststroke sleep-disordered breathing (SDB) has important implications for SDB screening and the pathophysiology of poststroke SDB. Within a large, population-based study, we assessed whether brainstem infarction location is associated with SDB presence and severity.

METHODS

Cross-sectional study was conducted on ischemic stroke patients in the Brain Attack Surveillance in Corpus Christi (BASIC) project. Subjects underwent SDB screening (median 13days after stroke) with a well-validated cardiopulmonary sleep apnea-testing device (n=355). Acute infarction location was determined based on review of radiology reports and dichotomized into brainstem involvement or none. Logistic and linear regression models were used to test the associations between brainstem involvement and SDB or apnea/hypopnea index (AHI) in unadjusted and adjusted models.

RESULTS

A total of 38 participants (11%) had acute infarction involving the brainstem. Of those without brainstem infarction, 59% had significant SDB (AHI⩾10); the median AHI was 13 (interquartile range (IQR) 6, 26). Of those with brainstem infarction, 84% had SDB; median AHI was 20 (IQR 11, 38). In unadjusted analysis, brainstem involvement was associated with over three times the odds of SDB (odds ratio (OR) 3.71 (95% confidence interval (CI): 1.52, 9.13)). In a multivariable model, adjusted for demographics, body mass index (BMI), hypertension, diabetes, coronary artery disease, atrial fibrillation, prior stroke/transient ischemic attack (TIA), and stroke severity, results were similar (OR 3.76 (95% CI: 1.44, 9.81)). Brainstem infarction was also associated with AHI (continuous) in unadjusted (p=0.004) and adjusted models (p=0.004).

CONCLUSIONS

Data from this population-based stroke study show that acute infarction involving the brainstem is associated with both presence and severity of SDB.

Is technologist review of raw data necessary after home studies for sleep apnea?

STUDY OBJECTIVES

As the importance of portable monitors for detection of sleep apnea increases, efficient and cost-minimizing methods for data interpretation are needed. We sought to compare in stroke patients, for whom portable studies often have particular advantages, results from a cardiopulmonary monitoring device with and without manual edits by a polysomnographic technologist.

METHODS

Participants in an ongoing stroke surveillance study in Corpus Christi, Texas, underwent sleep apnea assessments with the ApneaLink Plus device within 45 days of stroke onset. Recordings were analyzed by the device's software unedited, and again after edits were made to the raw data by a registered polysomnographic technologist. Sensitivity and specificity were calculated, with the edited data as the reference standard. Sleep apnea was defined by 3 different apnea-hypopnea index (AHI) thresholds: ≥ 5, ≥ 10, and ≥ 15.

RESULTS

Among 327 subjects, 54% were male, 59% were Hispanic, and the median age was 65 years (interquartile range: 57, 77). The median AHI for the unedited data was 9 (4, 22), and for the edited data was 13 (6, 27) (p < 0.01). Specificity was above 98% for each AHI cutoff, while sensitivity was 81% to 82%. For each cutoff threshold, the edited data yielded a higher proportion of positive sleep apnea screens (p < 0.01) by approximately 10% in each group.

CONCLUSIONS

For stroke patients assessed with a cardiopulmonary monitoring device, manual editing by a technologist appears likely to improve sensitivity, whereas specificity of unedited data is already excellent.

Computed tomography findings for intracerebral hemorrhage have little incremental impact on post-stroke mortality prediction model performance

BACKGROUND

Stroke outcome studies often combine cases of intracerebral hemorrhage (ICH) and ischemic stroke (IS). These studies of mixed stroke typically ignore computed tomography (CT) findings for ICH cases, though the impact of omitting these traditional predictors of ICH mortality is unknown. We investigated the incremental impact of ICH CT findings on mortality prediction model performance.

METHODS

Cases of ICH and IS (2000-2003) were identified from the Brain Attack Surveillance in Corpus Christi (BASIC) project. Base models predicting 30-day mortality included demographics, stroke type, and clinical findings (National Institutes of Health Stroke Scale (NIHSS) +/- Glasgow Coma Scale (GCS)). The impact of adding CT data (volume, intraventricular hemorrhage, infratentorial location) was assessed with the area under the curve (AUC), unweighted sum of squared residuals (Ŝ), and integrated discrimination improvement (IDI). The model assessment was performed first for the mixed case of IS and ICH, and then repeated for ICH cases alone to determine whether any lack of improvement in model performance with CT data for mixed stroke type was due to IS cases naturally forming a larger proportion of the total sample than ICH.

RESULTS

A total of 1,256 cases were included (86% IS, 14% ICH). Thirty-day mortality was 16% overall (11% for IS; 43% for ICH). When both clinical scales (NIHSS and GCS) were included, none of the model performance measures showed improvement with the addition of CT findings whether considering IS and ICH together (ΔAUC: 0.002, 95% CI -0.01, 0.02; ΔŜ: -3.0, 95% CI -9.1, 2.6; IDI: 0.017, 95% CI -0.004, 0.05) or considering ICH cases alone (ΔAUC: 0.02, 95% CI -0.02, 0.08; ΔŜ: -2.0, 95% CI -9.7, 3.4; IDI 0.065, 95% CI -0.03, 0.21). If NIHSS was the only clinical scale included, there was still no improvement in AUC or Ŝ when CT findings were added for the sample with IS/ICH combined (ΔAUC: 0.005, 95% CI -0.01, 0.02; ΔŜ: -5.0, 95% CI -11.6, 1.0) or for ICH cases alone (ΔAUC: 0.05, 95% CI -0.002, 0.11; ΔŜ: -4.2, 95% CI -11.5, 2.3). However, IDI was improved when NIHSS was the only clinical scale for IS/ICH combined (IDI: 0.029, 95% CI 0.002, 0.065) and ICH alone (IDI: 0.12, 95% CI 0.005, 0.26).

CONCLUSIONS

Excluding ICH CT findings had only minimal impact on mortality prediction model performance whether examining ICH and IS together or ICH alone. These findings have important implications for the design of clinical studies involving ICH patients.

Impact of angiotensin-converting enzyme inhibitors administration prior to acute ischemic stroke onset on in-hospital mortality

INTRODUCTION

Angiotensin-converting enzyme inhibitors (ACEIs) have shown promising results in decreasing the incidence and the severity of ischemic stroke in populations at risk and in improving ischemic stroke outcomes.

OBJECTIVES

The objectives of this study were to investigate the impact of ACEI use before ischemic stroke onset on in-hospital mortality and to identify the independent predictors of in-hospital mortality among patients with ischemic stroke.

METHODS AND MATERIALS

A retrospective cohort study of all patients with acute ischemic stroke attending the hospital from June 1, 2008 to November 30, 2008 was performed. Data were collected from medical records and included demographic information, diagnostic information, risk factors, previous ACEI use, and vital discharge status. Statistical Package for Social Sciences (SPSS) version 15 was used for data analysis.

RESULTS

A total of 327 patients with acute ischemic stroke were studied, of which 119 (36.4%) had documented previous ACEI use. During the study period, 52 (15.9%) of the patients with acute ischemic stroke died in hospital. In-hospital mortality was significantly lower among patients who were on ACEI before the attack (P = 0.002). The independent predictors for in-hospital mortality among patients with ischemic stroke were age >or=65 years (P < .001), the presence of diabetes mellitus (P = .012), renal impairment (P = .002), and heart failure (P = .001). Moreover, prior use of ACEI was an independent predictor for survival after ischemic stroke attack (P < .001).

CONCLUSION

This study provides evidence that the prophylactic administration of ACEI before ischemic stroke may be a potential life-saving strategy. Furthermore, knowledge of in-hospital mortality predictors is necessary to improve survival rate after acute stroke.

Population-based analysis of the impact of expanding the time window for acute stroke treatment

BACKGROUND AND PURPOSE

Currently, a major focus on expanding acute ischemic stroke treatment opportunities centers on the development of drugs and devices with longer time windows for use. We sought to determine the time intervals within which stroke patients present to establish whether time window expansion will translate into more treatment.

METHODS

Data were derived from the Brain Attack Surveillance in Corpus Christi project, a population-based stroke surveillance study in an urban, southeast Texas county. This community does not contain an academic medical center, thus providing a "real-world" setting to capture patient arrival times. Onset time was recorded from the chart according to a prespecified methodology.

RESULTS

From January 2000 to June 2005, 2347 patients with acute ischemic stroke were validated. The mean age was 71 years, and 53% were female. Thirty-one percent presented within 3 hours of symptom onset; 13% between 3 and 6 hours; and 15% between 6 and 12 hours. Forty-one percent presented beyond 12 hours from symptom onset. Nearly half of patients with moderate and severe strokes presented in the 0- to 3-hour time window, whereas only 28% of mildly affected patients presented early.

CONCLUSIONS

This population-based study provides estimates of time to presentation in a representative community without tertiary referral bias. These data are useful for planning acute stroke therapy interventions and suggest that in addition to developing therapies with expanded time windows, research resources should also be devoted to reducing hospital presentation delays.

Presentation of intracerebral haemorrhage in a community

BACKGROUND

Studies on intracerebral haemorrhage (ICH) from tertiary care centres may not be an accurate representation of the true spectrum of disease presentation.

OBJECTIVE

To describe the clinical and imaging presentation of ICH in a community devoid of the referral bias of an academic medical centre; and to investigate factors associated with lower Glasgow coma scale (GCS) score at presentation, as GCS is crucial to early clinical decision making.

METHODS

The study formed part of the BASIC project (Brain Attack Surveillance in Corpus Christi), a population based stroke surveillance study in a bi-ethnic Texas community. Cases of first non-traumatic ICH were identified from years 2000 to 2003, using active and passive surveillance. Clinical data were collected from medical records by trained abstractors, and all computed tomography (CT) scans were reviewed by a study physician. Multivariable linear regression was used to identify clinical and CT predictors of a lower GCS score.

RESULTS

260 cases of non-traumatic ICH were identified. Median ICH volume was 11 ml (interquartile range 3 to 36) with hydrocephalus noted in 45%. Median initial GCS score was 12.5 (7 to 15). Hydrocephalus score (p = 0.0014), ambient cistern effacement (p = 0.0002), ICH volume (p = 0.014), and female sex (p = 0.024) were independently associated with lower GCS score at presentation, adjusting for other variables.

CONCLUSIONS

ICH has a wide range of severity at presentation. Hydrocephalus is a potentially reversible cause of a lower GCS score. Since early withdrawal of care decisions are often based on initial GCS, recognition of the important influence of hydrocephalus on GCS is warranted before withdrawal of care decisions are made.

Emergency department evaluation of ischemic stroke and TIA: the BASIC Project

OBJECTIVE

To identify demographic and clinical variables of emergency department (ED) practices in a community-based acute stroke study.

METHODS

By both active and passive surveillance, the authors identified cerebrovascular disease cases in Nueces County, TX, as part of the Brain Attack Surveillance in Corpus Christi (BASIC) Project, a population-based stroke surveillance study, between January 1, 2000, and December 31, 2002. With use of multivariable logistic regression, variables independently associated with three separate outcomes were sought: hospital admission, brain imaging in the ED, and neurologist consultation in the ED. Prespecified variables included age, sex, ethnicity, insurance status, NIH Stroke Scale score, type of stroke (ischemic stroke or TIA), vascular risk factors, and symptom presentation variables. Percentage use of recombinant tissue plasminogen activator (rt-PA) was calculated.

RESULTS

A total of 941 Mexican Americans (MAs) and 855 non-Hispanic whites (NHWs) were seen for ischemic stroke (66%) or TIA (34%). Only 8% of patients received an in-person neurology consultation in the ED, and 12% did not receive any head imaging. TIA was negatively associated with neurology consultations compared with completed stroke (odds ratio [OR] 0.35 [95% CI 0.21 to 0.57]). TIA (OR 0.14 [0.10 to 0.19]) and sensory symptoms (OR 0.59 [0.44 to 0.81]) were also negatively associated with hospital admission. MAs (OR 0.58 [0.35 to 0.98]) were less likely to have neurology consultations in the ED than NHWs. Only 1.7% of patients were treated with rt-PA.

CONCLUSIONS

Neurologists are seldom involved with acute cerebrovascular care in the emergency department (ED), especially in patients with TIA. Greater neurologist involvement may improve acute stroke diagnosis and treatment efforts in the ED.

Family history of stroke among Mexican-American and non-Hispanic white patients with stroke and TIA: implications for the feasibility and design of stroke genetics research

Family history of stroke may differ by ethnicity. This study examined the associations of ethnicity and stroke risk factors with family history of stroke using data from the Brain Attack Surveillance in Corpus Christi Project. A random sample of stroke/transient ischemic attack cases was interviewed about family history of stroke (n = 524). Thirty-six percent of the cases reported a family history of stroke, with 26% reporting a parental and 13% a sibling history. Compared to non-Hispanic whites (NHWs), Mexican-Americans (MAs) were two times (OR = 2.07; 95% CI: 1.09-3.95) more likely to have a sibling with stroke. More MAs (8.1%; 95% CI: 4.6-11.6) had living siblings with stroke compared to NHWs (1.9%; 95% CI: 0.1-3.8). Since MAs are more likely to have living siblings with stroke compared with NHWs, MAs may be a more feasible population for family stroke studies than predominantly white populations.

Excess stroke in Mexican Americans compared with non-Hispanic Whites: the Brain Attack Surveillance in Corpus Christi Project

Mexican Americans are the largest subgroup of Hispanics, the largest minority population in the United States. Stroke is the leading cause of disability and third leading cause of death. The authors compared stroke incidence among Mexican Americans and non-Hispanic Whites in a population-based study. Stroke cases were ascertained in Nueces County, Texas, utilizing concomitant active and passive surveillance. Cases were validated on the basis of source documentation by board-certified neurologists masked to subjects' ethnicity. From January 2000 to December 2002, 2,350 cerebrovascular events occurred. Of the completed strokes, 53% were in Mexican Americans. The crude cumulative incidence was 168/10,000 in Mexican Americans and 136/10,000 in non-Hispanic Whites. Mexican Americans had a higher cumulative incidence for ischemic stroke (ages 45-59 years: risk ratio = 2.04, 95% confidence interval: 1.55, 2.69; ages 60-74 years: risk ratio = 1.58, 95% confidence interval: 1.31, 1.91; ages >or=75 years: risk ratio = 1.12, 95% confidence interval: 0.94, 1.32). Intracerebral hemorrhage was more common in Mexican Americans (age-adjusted risk ratio = 1.63, 95% confidence interval: 1.24, 2.16). The subarachnoid hemorrhage age-adjusted risk ratio was 1.57 (95% confidence interval: 0.86, 2.89). Mexican Americans experience a substantially greater ischemic stroke and intracerebral hemorrhage incidence compared with non-Hispanic Whites. As the Mexican-American population grows and ages, measures to target this population for stroke prevention are critical.

Stroke Risk After Transient Ischemic Attack in a Population-Based Setting

BACKGROUND AND PURPOSE

Stroke risk after transient ischemic attack (TIA) has not been examined in an ethnically diverse population-based community setting. The purpose of this study was to identify stroke risk among TIA patients in a population-based cerebrovascular disease surveillance project.

METHODS

The Brain Attack Surveillance in Corpus Christi (BASIC) Project prospectively ascertains stroke and TIA cases in a geographically isolated Southeast Texas County. The community is approximately half Mexican American and half nonHispanic white. Cases are validated by board-certified neurologists using source documentation. Cumulative risk for stroke after TIA was determined using Kaplan-Meier estimates. Cox proportional hazards regression was used to test for associations between stroke risk after TIA and demographics, symptoms, risk factors, and history of stroke/TIA.

RESULTS

BASIC identified 612 TIA cases between January 1, 2000, and December 31, 2002; 60.9% were female and 48.0% were Mexican American. Median age was 73.8 years. Stroke risk within 2 days, 7 days, 30 days, 90 days, and 12 months was 1.64%, 1.97%, 3.15%, 4.03%, and 7.27%, respectively. Stroke risk was not influenced by ethnicity, symptoms, or risk factors.

CONCLUSIONS

Using a population-based design, we found that early stroke risk after TIA was less than previously reported in this bi-ethnic population of Mexican Americans and nonHispanic whites. Approximately half of the 90-day stroke risk after TIA occurred within 2 days.

Access to Care, Acculturation, and Risk Factors for Stroke in Mexican Americans

Background and Purpose— Mexican Americans are the largest subgroup of Hispanic Americans, now the most numerous US minority population. We compared access to care, acculturation, and biological risk factors among Mexican American and non-Hispanic white stroke patients and the general population.

Methods— The Brain Attack Surveillance in Corpus Christi project is a population-based stroke surveillance study conducted in southeast Texas. All stroke cases were ascertained through active and passive surveillance from January 2000 through April 2002 and compared with population estimates from a random-digit telephone survey.

Results— Compared with non-Hispanic white stroke patients (n=405), Mexican American stroke patients (n=403) were less likely to have graduated from high school (odds ratio [OR], 15.4; 95% confidence interval [CI], 10.6 to 22.4) and more likely to earn less than $20 000 per year (OR, 6.5; 95% CI, 4.5 to 9.4). Mexican American stroke patients were more likely to have diabetes (OR, 2.7; 95% CI, 2.0 to 3.7) and less likely to have atrial fibrillation (OR, 0.5; 95% CI, 0.4 to 0.8). Compared with population estimates (n=719), stroke was associated with diabetes (Mexican Americans: OR, 3.6; 95% CI, 2.2 to 5.8; non-Hispanic whites: OR, 3.0; 95% CI, 1.7 to 5.5), hypertension (Mexican Americans: OR, 2.8; 95% CI, 1.8 to 4.3; non-Hispanic whites: OR, 3.3; 95% CI, 2.2 to 5.0), lower incomes (Mexican Americans: OR, 3.4; 95% CI, 2.1 to 5.4; non-Hispanic whites: OR, 3.0; 95% CI, 1.7 to 5.2), and lower educational attainment (Mexican Americans: OR, 5.1; 95% CI, 3.2 to 8.1; non-Hispanic whites: OR, 4.5; 95% CI, 2.2 to 9.3).

Conclusions— Biological and social variables are associated with stroke to a similar extent in both Mexican Americans and non-Hispanic whites. Health behavior interventions for both populations may follow from this work. Stroke disparities between these populations may be explained only partially by differences in the prevalence of currently identified biological and social factors.