Novel functional insights into ischemic stroke biology provided by the first genome-wide association study of stroke in indigenous Africans.

BACKGROUND: African ancestry populations have the highest burden of stroke worldwide, yet the genetic basis of stroke in these populations is obscure. The Stroke Investigative Research and Educational Network (SIREN) is a multicenter study involving 16 sites in West Africa. We conducted the first-ever genome-wide association study (GWAS) of stroke in indigenous Africans. METHODS: Cases were consecutively recruited consenting adults (aged > 18 years) with neuroimaging-confirmed ischemic stroke. Stroke-free controls were ascertained using a locally validated Questionnaire for Verifying Stroke-Free Status. DNA genotyping with the H3Africa array was performed, and following initial quality control, GWAS datasets were imputed into the NIH Trans-Omics for Precision Medicine (TOPMed) release2 from BioData Catalyst. Furthermore, we performed fine-mapping, trans-ethnic meta-analysis, and in silico functional characterization to identify likely causal variants with a functional interpretation. RESULTS: We observed genome-wide significant (P-value < 5.0E-8) SNPs associations near AADACL2 and miRNA (MIR5186) genes in chromosome 3 after adjusting for hypertension, diabetes, dyslipidemia, and cardiac status in the base model as covariates. SNPs near the miRNA (MIR4458) gene in chromosome 5 were also associated with stroke (P-value < 1.0E-6). The putative genes near AADACL2, MIR5186, and MIR4458 genes were protective and novel. SNPs associations with stroke in chromosome 2 were more than 77 kb from the closest gene LINC01854 and SNPs in chromosome 7 were more than 116 kb to the closest gene LINC01446 (P-value < 1.0E-6). In addition, we observed SNPs in genes STXBP5-AS1 (chromosome 6), GALTN9 (chromosome 12), FANCA (chromosome 16), and DLGAP1 (chromosome 18) (P-value < 1.0E-6). Both genomic regions near genes AADACL2 and MIR4458 remained significant following fine mapping. CONCLUSIONS: Our findings identify potential roles of regulatory miRNA, intergenic non-coding DNA, and intronic non-coding RNA in the biology of ischemic stroke. These findings reveal new molecular targets that promise to help close the current gaps in accurate African ancestry-based genetic stroke's risk prediction and development of new targeted interventions to prevent or treat stroke.

Patient-level and system-level determinants of stroke fatality across 16 large hospitals in Ghana and Nigeria: a prospective cohort study.

BACKGROUND: Every minute, six indigenous Africans develop new strokes. Patient-level and system-level contributors to early stroke fatality in this region are yet to be delineated. We aimed to identify and quantify the contributions of patient-level and system-level determinants of inpatient stroke fatality across 16 hospitals in Ghana and Nigeria. METHODS: The Stroke Investigative Research and Educational Network (SIREN) is a multicentre study involving 16 sites in Ghana and Nigeria. Cases include adults (aged ≥18 years) with clinical and radiological evidence of an acute stroke. Data on stroke services and resources available at each study site were collected and analysed as system-level factors. A host of demographic and clinical variables of cases were analysed as patient-level factors. A mixed effect log-binomial model including both patient-level and system-level covariates was fitted. Results are presented as adjusted risk ratios (aRRs) with respective 95% CIs. FINDINGS: Overall, 814 (21·8%) of the 3739 patients admitted with stroke died as inpatients: 476 (18·1%) of 2635 with ischaemic stroke and 338 (30·6%) of 1104 with intracerebral haemorrhage. The variability in the odds of stroke fatality that could be attributed to the system-level factors across study sites assessed using model intracluster correlation coefficient was substantial at 7·3% (above a 5% threshold). Stroke units were available at only five of 16 centres. The aRRs of six patient-level factors associated with stroke fatality were: low vegetable consumption, 1·19 (95% CI 1·07-1·33); systolic blood pressure, 1·02 (1·01-1·04) for each 10 mm Hg rise; stroke lesion volume more than 30 cm3, 1·48 (1·22-1·79); National Institutes of Health Stroke Scale (NIHSS) score, 1·20 (1·13-1·26) for each 5-unit rise; elevated intracranial pressure, 1·75 (1·31-2·33); and aspiration pneumonia, 1·79 (1·16-2·77). INTERPRETATION: Studies are needed to assess the efficacy of interventions targeting patient-level factors such as aspiration pneumonia in reducing acute stroke fatality in this region. Policy directives to improve stroke unit access are warranted. FUNDING: US National Institutes of Health. TRANSLATIONS: For the Twi, Yoruba and Hausa translations of the abstract see Supplementary Materials section.

Differential associations between pre-diabetes, diabetes and stroke occurrence among West Africans.

BACKGROUND: There are limited data from Africa on the burden and associations between pre-diabetes (pre-DM), diabetes mellitus (DM) and stroke occurrence in a region experiencing a profound rise in stroke burden. PURPOSE: To characterize the associations between stroke and dysglycemic status among West Africans. METHODS: The Stroke Investigative Research and Educational Network (SIREN) is a multicenter, case-control study involving 15 sites in Ghana and Nigeria. Cases include adults aged ≥18 years with clinical and radiological evidence of an acute stroke. Controls were age-and-gender matched stroke-free adults. Detailed evaluations for vascular factors were performed. Pre-diabetes was defined as HBA1c of 5.7%-6.4% or Fasting blood glucose (FBG) 5.6-7.0 mmol/L and DM as HBA1c >6.5% or FBG>7.0 mmol/L. We used conditional logistic regression to estimate adjusted odds ratios (aOR) with 95% Confidence Interval. RESULTS: Among 2,935 stroke cases the mean age was 60.0 ± 14.2 years with 55.2% being males. By glycemic status, 931 (31.7%) were euglycemic, 633 (21.6%) had Pre-diabetes and 1371 (46.7%) had DM. Of the age- and sex-matched stroke-free controls 69.2% were euglycemic, 13.3% had pre-DM and 17.5% had DM. Pre-DM [aOR (95% CI): 3.68(2.61-5.21)] and DM [4.29 (3.19-5.74)] were independently associated with stroke. The aOR of Pre-DM for ischemic stroke 3.06 (2.01-4.64)] was lower than 4.82 (3.37-6.89) for DM. However, the aOR of Pre-DM for hemorrhagic stroke 6.81 (95% CI: 3.29 - 14.08)] was higher than 3.36 (1.94-5.86) for DM. Furthermore, the aOR of pre-DM for ischemic stroke subtypes were 9.64 (1.30-71.57) for cardio-embolic stroke, 3.64 (1.80-7.34) for small-vessel occlusive disease and 4.63 (0.80-26.65) for large-vessel disease. CONCLUSION: Pre-DM is strongly and independently associated with stroke in Africans. Improving glycemic control through screening, healthy lifestyle and pharmacotherapy at a population level may be strategic in reducing the rising burden of stroke in Africa.

Unraveling the risk factors for spontaneous intracerebral hemorrhage among West Africans.

OBJECTIVE: To characterize risk factors for spontaneous intracerebral hemorrhage (sICH) occurrence and severity among West Africans. METHODS: The Stroke Investigative Research and Educational Network (SIREN) study is a multicenter case-control study involving 15 sites in Ghana and Nigeria. Patients were adults ≥18 years old with CT-confirmed sICH with age-, sex-, and ethnicity-matched stroke-free community controls. Standard instruments were used to assess vascular, lifestyle, and psychosocial factors. Factors associated with sICH and its severity were assessed using conditional logistic regression to estimate odds ratios (ORs) and population-attributable risks (PARs) with 95% confidence intervals (CIs) for factors. RESULTS: Of 2,944 adjudicated stroke cases, 854 were intracerebral hemorrhage (ICH). Mean age of patients with ICH was 54.7 ± 13.9 years, with a male preponderance (63.1%), and 77.3% were nonlobar. Etiologic subtypes of sICH included hypertension (80.9%), structural vascular anomalies (4.0%), cerebral amyloid angiopathy (0.7%), systemic illnesses (0.5%), medication-related (0.4%), and undetermined (13.7%). Eight factors independently associated with sICH occurrence by decreasing order of PAR with their adjusted OR (95% CI) were hypertension, 66.63 (20.78-213.72); dyslipidemia, 2.95 (1.84-4.74); meat consumption, 1.55 (1.01-2.38); family history of CVD, 2.22 (1.41-3.50); nonconsumption of green vegetables, 3.61 (2.07-6.31); diabetes mellitus, 2.11 (1.29-3.46); stress, 1.68 (1.03-2.77); and current tobacco use, 14.27 (2.09-97.47). Factors associated with severe sICH using an NIH Stroke Scale score >15 with adjusted OR (95% CI) were nonconsumption of leafy green vegetables, 2.03 (1.43-2.88); systolic blood pressure for each mm Hg rise, 1.01 (1.00-1.01); presence of midline shift, 1.54 (1.11-2.13); lobar ICH, 1.72 (1.16-2.55); and supratentorial bleeds, 2.17 (1.06-4.46). CONCLUSIONS: Population-level control of the dominant factors will substantially mitigate the burden of sICH in West Africa.

Biobanking in a Challenging African Environment: Unique Experience from the SIREN Project.

Africa was previously insufficiently represented in the emerging discipline of biobanking despite commendable early efforts. However, with the Human, Heredity, and Health in Africa (H3Africa) initiative, biorepository science has been bolstered, regional biobanks are springing up, and awareness about biobanks is growing on the continent. The Stroke Investigative Research and Educational Network (SIREN) project is a transnational, multicenter, hospital and community-based study involving over 3000 cases and 3000 controls recruited from 16 sites in Ghana and Nigeria. SIREN aims to explore and unravel the genetic and environmental factors that interact to produce the peculiar phenotypic and clinical characteristics of stroke as seen in people of African ancestry and facilitate the development of new diagnostics, therapeutics, and preventative strategies. The aim of this article is to describe our experience with the development of the procedure for collection, processing, storage, and shipment of biological samples (blood, serum, plasma, buffy coat, red cell concentrates, and DNA) and brain imaging across coordinating and participating sites within the SIREN Project. The SIREN network was initiated in 2014 with support and funding from the H3Africa Initiative. The SIREN Biobank currently has 3015 brain images, 92,950 blood fractions (serum, plasma, red cell concentrates, and buffy coat) accrued from 8450 recruited subjects, and quantified and aliquoted good-quality DNA extracts from 6150 study subjects. This represents an invaluable resource for future research with expanding genomic and trans-omic technologies. This will facilitate the involvement of indigenous African samples in cutting-edge stroke genomics and trans-omics research. It is, however, critical to effectively engage African stroke patients and community members who have contributed precious biological materials to the SIREN Biobank to generate appropriate evidence base for dealing with ethical, legal, and social issues of privacy, autonomy, identifiability, biorights, governance issues, and public understanding of stroke biobanking in the context of unique African culture, language, and belief systems.