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.

A Novel Afrocentric Stroke Risk Assessment Score: Models from the Siren Study.

BACKGROUND: Stroke risk can be quantified using risk factors whose effect sizes vary by geography and race. No stroke risk assessment tool exists to estimate aggregate stroke risk for indigenous African. OBJECTIVES: To develop Afrocentric risk-scoring models for stroke occurrence. MATERIALS AND METHODS: We evaluated 3533 radiologically confirmed West African stroke cases paired 1:1 with age-, and sex-matched stroke-free controls in the SIREN study. The 7,066 subjects were randomly split into a training and testing set at the ratio of 85:15. Conditional logistic regression models were constructed by including 17 putative factors linked to stroke occurrence using the training set. Significant risk factors were assigned constant and standardized statistical weights based on regression coefficients (ß) to develop an additive risk scoring system on a scale of 0-100%. Using the testing set, Receiver Operating Characteristics (ROC) curves were constructed to obtain a total score to serve as cut-off to discriminate between cases and controls. We calculated sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) at this cut-off. RESULTS: For stroke occurrence, we identified 15 traditional vascular factors. Cohen's kappa for validity was maximal at a total risk score of 56% using both statistical weighting approaches to risk quantification and in both datasets. The risk score had a predictive accuracy of 76% (95%CI: 74-79%), sensitivity of 80.3%, specificity of 63.0%, PPV of 68.5% and NPV of 76.2% in the test dataset. For ischemic strokes, 12 risk factors had predictive accuracy of 78% (95%CI: 74-81%). For hemorrhagic strokes, 7 factors had a predictive accuracy of 79% (95%CI: 73-84%). CONCLUSIONS: The SIREN models quantify aggregate stroke risk in indigenous West Africans with good accuracy. Prospective studies are needed to validate this instrument for stroke prevention.

A Nationwide Survey of Parkinson's Disease Medicines Availability and Affordability in Nigeria.

BACKGROUND AND OBJECTIVES: Limited access to medicines can impact negatively on outcomes in people with Parkinson's disease (PD). The study objectives were to determine the availability and assess the affordability of antiparkinsonian medications in pharmacies across Nigeria. METHODS: This was a cross-sectional nationwide study utilizing the World Health Organization/Health Action Initiative methodology. Strategically selected private- and public-sector pharmacies in the six geopolitical zones of Nigeria were surveyed for availability of medicines for management of early and advanced PD. The nine categories were: levodopa/peripheral decarboxylase inhibitors, dopamine receptor agonists, monoamine oxidase type B inhibitors, anticholinergics, catechol-o-methyl transferase inhibitors, atypical antipsychotics, antidepressants, antidementia drugs, and miscellaneous (e.g., drugs for orthostatism, urinary incontinence, and sleep disturbance). Unaffordability was defined as paying more than 1 days' wages (>N600 or > US$1.67) for a standard 30-day supply. RESULTS: One hundred twenty-three pharmacies were surveyed (62 private [50.4%] and 61 public sector [49.6%]; range of 15-25 pharmacies in each geopolitical zone). Private exceeded public-sector availability across all nine categories of PD medicines (P < 0.05). The most available medicines were dopamine receptor agonists (68.3%; predominantly ergot-derived bromocriptine), anticholinergics (56.1%; mainly trihexyphenidyl), and l-dopa formulations (48%; mainly 250/25 l-dopa/carbidopa). Only two medications (trihexyphenidyl tablets and biperiden injection) were affordable. The average number of day's minimum wages for a 30-day supply of PD medicines was 41.3 days (range, 1-371). CONCLUSIONS: PD medicines access is limited in Nigeria. Strategies, including engagement of stakeholders to consider interventions to improve and prioritize PD medicines access, are urgently warranted.