Bio-Repository of DNA in stroke (BRAINS): a study protocol

Diabetes mellitus and obesity among South Asians with ischemic stroke across three countries

BACKGROUND

Diabetes mellitus and central obesity are more common among South Asian populations than among White British people. This study explores the differences in diabetes and obesity in South Asians with stroke living in the United Kingdom, India, and Qatar compared with White British stroke patients.

METHODS

The study included the UK, Indian, and Qatari arms of the ongoing large Bio-Repository of DNA in Stroke (BRAINS) international prospective hospital-based study for South Asian stroke. BRAINS includes 4580 South Asian and White British recruits from UK, Indian, and Qatar sites with first-ever ischemic stroke.

RESULTS

The study population comprises 1751 White British (WB) UK residents, 1165 British South Asians (BSA), 1096 South Asians in India (ISA), and 568 South Asians in Qatar (QSA). ISA, BSA, and QSA South Asians suffered from higher prevalence of diabetes compared with WB by 14.5% (ISA: 95% confidence interval (CI) = 18.6-33.0, p < 0.001), 31.7% (BSA: 95% CI = 35.1-50.2, p < 0.001), and 32.7% (QSA: 95% CI = 28.1-37.3, p < 0.001), respectively. Although WB had the highest prevalence of body mass index (BMI) above 27 kg/m2 compared with South Asian patients (37% vs 21%, p < 0.001), South Asian patients had a higher waist circumference than WB (94.8 cm vs 90.8 cm, p < 0.001). Adjusting for traditional stroke risk factors, ISA, BSA, and QSA continued to display an increased risk of diabetes compared with WB by 3.28 (95% CI: 2.53-4.25, p < 0.001), 3.61 (95% CI: 2.90-4.51, p < 0.001), and 5.24 (95% CI: 3.93-7.00, p < 0.001), respectively.

CONCLUSION

South Asian ischemic stroke patients living in Britain and Qatar have a near 3.5-fold risk of diabetes compared with White British stroke patients. Their body composition may partly help explain that increased risk. These findings have important implications for public health policymakers in nations with large South Asian populations.

Cigarette smoking as a risk factor for ischaemic stroke in young South Asian male migrants to Qatar: The BRAINS study

BACKGROUND

The incidence of stroke in the Middle East is high, given its relatively young population. Smoking is a well-recognized risk factor for ischaemic stroke, and its high regional prevalence may partly account for this increased stroke risk. This research aims to determine whether young male South Asian migrants in Qatar were adversely affected by stroke depending on their smoking status.

METHODS

Data from the ongoing international prospective BRAINS study was analysed. Male South Asian migrants to Qatar with a history of ischaemic stroke were recruited. Multivariate regression analysis was used to estimate the effects of comorbidities, such as BMI, hypertension, diabetes, hypercholesterolemia, alcohol consumption, and ischemic heart disease, on the association of age of stroke onset and smoking status.

RESULTS

We identified 778 (mean age 49.5±10.2) migrant male workers of South Asian descent with ischaemic stroke in Qatar, of which 41.3% of the sample were current smokers. Compared to non-smokers, current smokers suffered a stroke 2.03 years earlier (95%CI: 0.60-3.46, P=0.005). Multivariate regression analysis demonstrated that only current smoking status was associated with an earlier age of stroke onset (β=2.03, SE=0.74, P=0.006).

CONCLUSION

Smoking is associated with at least a two-year earlier onset of ischaemic stroke in male South Asian migrants to the Middle East. Our study has important implications for the public health management of migrants in host countries.

Atrial fibrillation in UK South Asian hospitalized ischemic stroke patients: The BRAINS study

INTRODUCTION

South Asian diaspora comprise one of the largest ethnic minority groups in the world yet data about atrial fibrillation (AF) in this demographic is understudied. Our aim is to identify differences in AF prevalence and treatment between South Asians and white British stroke patients.

METHOD

The UK arm of a prospective ongoing large international repository on stroke was analysed. Ethnic differences in AF prevalence and management in those with ischemic stroke were analysed.

RESULTS

Of the 3515 individuals recruited with ischemic stroke, 1482 (men: 972, women: 510) were South Asian and 2033 (men:1141, women:892) of white British ethnicity. AF was present in 462 white British and 193 South Asians stroke patients, with South Asians displaying a lower prevalence of AF (South Asians: 13.0% vs white British 22.7%, P<0.001). Despite adjustment for traditional AF risk factors, South Asians had a significantly lower OR of AF compared to white British stroke patients (OR: 0.40, 95%CI: 0.33:0.49, P<0.001). Among confirmed AF cases, 31.8% of South Asians and 41.4% of white British were untreated at admission (P = 0.02). Antiplatelet treatment was significantly higher among South Asians at both admission (South Asian: 47.4% vs. white British: 29.9%, P<0.001) and discharge (South Asian: 49.5% vs. white British: 34.7%, P = 0.001), although anticoagulation treatment was similar across both ethnic groups at admission (South Asian: 28.5% vs white British: 28.1%, P = 0.93), and discharge (South Asian: 45.1% vs white British: 43.1%, P = 0.64).

CONCLUSION

Stroke patients of South Asian descent are at significantly lower risk of AF but more likely to be on antiplatelet treatment compared to their white British counterparts.

Ischaemic stroke in South Asians: The BRAINS study

BACKGROUND AND PURPOSE

Studies on stroke in South Asian populations are sparse. The aim of this study was to compare differences in age of onset of ischaemic stroke in South Asian patients living in the United Kingdom and South Asian patients living in India versus White British stroke patients.

METHODS

We studied the UK and Indian arms of the ongoing BRAINS study, an international prospective hospital-based study of South Asian stroke patients. The BRAINS study includes 4038 South Asian and White British patients with first-ever ischaemic stroke, recruited from sites in the United Kingdom and India.

RESULTS

Of the included patients, 1126 were South Asians living in India (ISA), while 1176 were British South Asian (BSA) and 1736 were White British (WB) UK residents. Patients in the ISA and BSA groups experienced stroke 19.5 years and 7.2 years earlier than their WB counterparts, respectively (mean [interquartile range] age: BSA 64.3 [22] years vs. ISA 52.0 [18] years vs. WB 71.5 [19] years; p < 0.001). Patients in the BSA group had higher rates of hypertension, diabetes mellitus and hypercholesterolaemia than those in the ISA and WB groups. After adjustment for traditional stroke risk factors, an earlier age of stroke onset of 18.9 years (p < 0.001) and 8.9 years (p < 0.001) was still observed in the ISA and BSA groups, respectively. In multivariable stepwise linear regression analysis, ethnicity accounted for 24.7% of the variance in early age onset.

CONCLUSION

Patients in the BSA and ISA groups experienced ischaemic stroke approximately 9 and 19 years earlier, respectively, than their WB counterparts. Ethnicity is an independent predictor of early age of stroke onset. Our study has considerable implications for public health policymakers in countries with sizable South Asian populations.

Current status of stroke in Qatar: Including data from the BRAINS study

Background

Qatar is located on the north-eastern coast of the Arabian Peninsula. Qatari natives account for less than 15% of the population while the largest migrant group comprising 60% derives from South Asia. Despite projections that stroke burden in Qatar will increase with population ageing, epidemiological studies focusing on stroke in Qatar are relatively scarce.

Method

We reviewed the available epidemiological publications relating to Qatar. In addition, we have added to this knowledge by incorporating Qatari data from the on-going Bio-Repository of DNA in Stroke, an independent multinational database of stroke patients.

Results

Qatar has low reported incidence and mortality rates of 58 and 9.17 per 100,000 per year, respectively, which may be explained by its middle-aged migrant worker majority population. Correspondingly, South Asian migrants in Qatar suffered younger strokes than Qatari natives (48.7 vs 63.4 years, P < 0.001). Among the most common risk factors identified in stroke patients were hypertension (77.9%), diabetes (43.8%) and hypercholesterolemia (28.5%). Ischaemic stroke was the most frequent subtype amongst migrant South Asians (71.1%). The majority of stroke cases had computed tomography and/or magnetic resonance imaging scans, but only 11.1% of ischaemic strokes were thrombolysed. Qataris on one-year follow up were more often found to have died (6.5% vs 0.3%) and had further stroke/transient ischaemic attack events (17.4% vs 6.4%, P = 0.009) compared to South Asians.

Conclusion

The burden of stroke is increasing in Qatar, and considerable disparities are observed between the native and migrant populations which likely will require different approaches to management by its healthcare system.

Joinville stroke biobank: study protocol and first year’s results

ABSTRACT Aiming to contribute to studies that use detailed clinical and genomic information of biobanks, we present the initial results of the first Latin American Stroke Biobank. Methods: Blood samples were collected from patients included in the Joinville Stroke Registry and four Brazilian cities. Demographic socio-economic data, cardiovascular risk factors, Causative Classification System for Ischemic Stroke, Trial of Org 10172 in Acute Stroke Treatment and National Institutes of Health scores, functional stroke status (modified Rankin) and brain images were recorded. Additionally, controls from both geographic regions were recruited. High-molecular-weight genomic DNA was obtained from all participants. Results: A total of 2,688 patients and 3,282 controls were included. Among the patients, 76% had ischemic stroke, 12% transient ischemic attacks, 9% hemorrhagic stroke and 3% subarachnoid hemorrhage. Patients with undetermined ischemic stroke were most common according the Trial of Org 10172 in Acute Stroke Treatment (40%) and Causative Classification System for Ischemic Stroke (47%) criteria. A quarter of the patients were under 55 years of age at the first-ever episode. Conclusions: We established the Joinville Stroke Biobank and discuss its potential for contributing to the understanding of the risk factors leading to stroke.

The Association of Coagulation Factor V (Leiden) and Factor II (Prothrombin) Mutations With Stroke

Background:

Epidemiological studies indicate that over the past forty years, the stroke incidence rates has increased. Factors V and II mutations are established genetic-variant risk factors for venous thrombosis; however, their contribution to stroke is a controversial issue.

Objectives:

This study aimed to investigate the potential association of FV and FII mutations with stroke in an Iranian population.

Patients and Methods:

The study population consisted of 153 patients of different stroke subtypes (except cryptogenic strokes), admitted to Ghaem Hospital, Mashhad, Iran. The control group included 153 age- and sex-matched subjects without a history of cerebrovascular or neurologic diseases. Mutations of FV and FII were determined by using a TaqMan SNP Genotyping technique. The chi-square and Exact Fisher tests were used to analyze the baseline characteristics. Results were as follows: The calculated P-value for sex and diabetes mellitus were 0.907 and 1.000, respectively. The case and control groups were also matched in low density lipoprotein (P = 0.816), high density lipoprotein (P = 0.323), triglyceride (P = 0.846), and total cholesterol (P = 0.079).

Results:

Analysis of the FV showed that none of the study subjects were AA homozygous for this mutation and only 6 heterozygous subjects were detected in the case and control groups. Regarding FII variants, none of the study subjects were AG heterozygous and only 1 AA homozygous was detected in the control group.

Conclusions:

The prevalence of both FV and FII variants are population based. Iran is an ethnically diverse country. Therefore, for a comprehensive analysis of a potential association of FV and/or FII mutations with stroke among Iranian population, epidemiological studies could be conducted among different ethnic groups.

Genetics of ischaemic stroke

Recent advances in genomics and statistical computation have allowed us to begin addressing the genetic basis of stroke at a molecular level. These advances are at the cusp of making important changes to clinical practice of some monogenic forms of stroke and, in the future, are likely to revolutionise the care provided to these patients. In this review we summarise the state of knowledge in ischaemic stroke genetics particularly in the context of how a practicing clinician can best use this knowledge.

Genome-wide analysis of blood pressure variability and ischemic stroke

BACKGROUND AND PURPOSE

Visit-to-visit variability in blood pressure (vBP) is associated with ischemic stroke. We sought to determine whether such variability has genetic causes and whether genetic variants associated with BP variability are also associated with ischemic stroke.

METHODS

A Genome Wide Association Study (GWAS) for loci influencing BP variability was undertaken in 3802 individuals from the Anglo-Scandinavian Cardiac Outcome Trial (ASCOT) study, in which long-term visit-to-visit and within-visit BP measures were available. Because BP variability is strongly associated with ischemic stroke, we genotyped the sentinel single nucleotide polymorphism in an independent ischemic stroke population comprising 8624 cases and 12 722 controls and in 3900 additional (Scandinavian) participants from the ASCOT study to replicate our findings.

RESULTS

The ASCOT discovery GWAS identified a cluster of 17 correlated single nucleotide polymorphisms within the NLGN1 gene (3q26.31) associated with BP variability. The strongest association was with rs976683 (P=1.4×10(-8)). Conditional analysis of rs976683 provided no evidence of additional independent associations at the locus. Analysis of rs976683 in patients with ischemic stroke found no association for overall stroke (odds ratio, 1.02; 95% CI, 0.97-1.07; P=0.52) or its subtypes: cardioembolic (odds ratio, 1.07; 95% CI, 0.97-1.16; P=0.17), large vessel disease (odds ratio, 0.98; 95% CI, 0.89-1.07; P=0.60), and small vessel disease (odds ratio, 1.07; 95% CI, 0.97-1.17; P=0.19). No evidence for association was found between rs976683 and BP variability in the additional (Scandinavian) ASCOT participants (P=0.18).

CONCLUSIONS

We identified a cluster of single nucleotide polymorphisms at the NLGN1 locus showing significant association with BP variability. Follow-up analyses did not support an association with risk of ischemic stroke and its subtypes.

Bio-repository of DNA in stroke: a study protocol of three ancestral populations

Stroke is a leading cause of death and disability in the world. Identifying the genes underlying stroke risk may help us to improve our understanding of the mechanisms that cause stroke and also identify novel therapeutic targets. To have sufficient power to disentangle the genetic component of stroke, large-scale highly phenotyped DNA repositories are necessary. The BRAINS (Bio-repository of DNA in stroke) study aims to recruit subjects with all subtypes of stroke as well as controls from UK, India, Sri Lanka and Qatar. BRAINS-UK will include 1500 stroke patients of European ancestry as well as British South Asians. BRAINS-South Asia aims to recruit 3000 stroke subjects and 3000 controls from across India and Sri Lanka. BRAINS-Middle East aims to enrol 1500 stroke patients from Qatar. The controls for BRAINS-Middle East will be recruited from a population-based Qatari Biobank. With the addition of new recruitment centres in India and Qatar, we present an updated version of the BRAINS study protocol. This is the first international DNA biobank for stroke patients and controls from the Middle East. By investigating the influence of genetic factors on stroke risk in European, South Asian and Middle Eastern populations, BRAINS has the potential to improve our understanding of genetic differences between these groups and may lead to new population-specific therapeutic targets.

Genomic risk profiling of ischemic stroke: results of an international genome-wide association meta-analysis

INTRODUCTION

Familial aggregation of ischemic stroke derives from shared genetic and environmental factors. We present a meta-analysis of genome-wide association scans (GWAS) from 3 cohorts to identify the contribution of common variants to ischemic stroke risk.

METHODS

This study involved 1464 ischemic stroke cases and 1932 controls. Cases were genotyped using the Illumina 610 or 660 genotyping arrays; controls, with Illumina HumanHap 550Kv1 or 550Kv3 genotyping arrays. Imputation was performed with the 1000 Genomes European ancestry haplotypes (August 2010 release) as a reference. A total of 5,156,597 single-nucleotide polymorphisms (SNPs) were incorporated into the fixed effects meta-analysis. All SNPs associated with ischemic stroke (P<1×10(-5)) were incorporated into a multivariate risk profile model.

RESULTS

No SNP reached genome-wide significance for ischemic stroke (P<5×10(-8)). Secondary analysis identified a significant cumulative effect for age at onset of stroke (first versus fifth quintile of cumulative profiles based on SNPs associated with late onset, ß = 14.77 [10.85,18.68], P = 5.5×10(-12)), as well as a strong effect showing increased risk across samples with a high propensity for stroke among samples with enriched counts of suggestive risk alleles (P<5×10(-6)). Risk profile scores based only on genomic information offered little incremental prediction.

DISCUSSION

There is little evidence of a common genetic variant contributing to moderate risk of ischemic stroke. Quintiles based on genetic loading of alleles associated with a younger age at onset of ischemic stroke revealed a significant difference in age at onset between those in the upper and lower quintiles. Using common variants from GWAS and imputation, genomic profiling remains inferior to family history of stroke for defining risk. Inclusion of genomic (rare variant) information may be required to improve clinical risk profiling.

The utility of collaborative biobanks for cardiovascular research

Differences between animal and human atherosclerosis have led to the requirement for clinical data, imaging information and biological material from large numbers of patients and healthy persons. Where such "biobanks" exist, they have been fruitful sources for genomewide association, diagnostic accuracy, ethnicity, and risk stratification cohort studies. In addition once established, they attract funding for future projects. Biobanks require a network of medical contributors, secure storage facilities, bioinformatics expertise, database managers, and ethical working practices to function optimally. There is the opportunity for collaboration between individual biobanks to further amplify the advantages afforded.