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1.  Epidemiology of stroke and its subtypes in Chinese vs white populations 
Neurology  2013;81(3):264-272.
We aimed to systematically assess the evidence for differences in the incidence of stroke and distribution of its subtypes in Chinese compared with white populations.
We comprehensively sought studies conducted since 1990 in Chinese populations of 1) first-ever stroke incidence (community-based studies only), and 2) pathologic types/subtypes of stroke (hospital- or community-based studies of first-ever or recurrent strokes). We identified community-based studies in white populations from a recent systematic review. For each study, we calculated age-standardized stroke incidence and the proportions of each pathologic type and ischemic subtype, using random-effects meta-analysis to pool proportions of stroke types/subtypes in Chinese and in white populations.
Age-standardized annual first-ever stroke incidence in community-based studies was higher among Chinese than white populations (for ages 45–74 years, range 205–584 vs 170–335 per 100,000, respectively). Intracerebral hemorrhage accounted for a larger, more variable proportion of strokes in China than Taiwan (range 27%–51% vs 17%–28%), in Chinese community-based than hospital-based studies (27%–51% vs 17%–30%), and in community-based Chinese than white studies (pooled proportion 33% vs 12%). Although the overall proportion of lacunar ischemic stroke appeared higher in Chinese than white populations, variable study methodologies precluded reliable comparisons.
There is good evidence for a slightly higher overall stroke incidence and higher proportion of intracerebral hemorrhage in Chinese vs white populations, but no clear evidence for different distributions of ischemic stroke subtypes. Studies using comparable, population-based case ascertainment and similar classification methods are needed to address this.
PMCID: PMC3770160  PMID: 23858408
2.  Ischaemic stroke is associated with the ABO locus: the Euroclot study 
Annals of neurology  2013;73(1):16-31.
End-stage coagulation and the structure/function of fibrin are implicated in the pathogenesis of ischaemic stroke. We explored whether genetic variants associated with end-stage coagulation in healthy volunteers account for the genetic predisposition to ischemic stroke and examined their influence on stroke subtype.
Common genetic variants identified through genome-wide association studies of coagulation factors and fibrin structure/function in healthy twins (n=2,100 Stage 1) were examined in ischemic stroke (n=4,200 cases) using 2 independent samples of European ancestry (Stage 2). A third clinical collection having stroke subtyping (total 8,900 cases 55,000 controls) was used for replication (Stage 3).
Stage 1 identified 524 SNPs from 23 LD blocks having significant association (p<5 ×10-8) with one or more coagulation/fibrin phenotypes. Most striking associations included SNP rs5985 with factor XIII activity (p=2.6×10-186), rs10665 with FVII (p = 2.4×10-47) and rs505922 in the ABO gene with both von Willebrand Factor (vWF p=4.7×10-57) and factor VIII (p=1.2×10-36). In Stage 2, the 23 independent SNPs were examined in stroke cases/non-cases using MORGAM and WTCCC2 collections. SNP rs505922 was nominally associated with ischaemic stroke, odds ratio = 0.94 (95% confidence intervals, 0.88-0.99), p=0.023. Independent replication in Meta-Stroke confirmed the rs505922 association with stroke, beta=0.066 (0.02) p = 0.001, a finding specific to large vessel and cardioembolic stroke (p = 0.001 and p = <0.001 respectively) but not seen with small vessel stroke (p=0.811).
ABO gene variants are associated with large vessel and cardioembolic stroke but not small vessel disease. This work sheds light on the different pathogenic mechanisms underpinning stroke subtype.
PMCID: PMC3582024  PMID: 23381943
GWAS; thrombosis; stroke; coagulation factor; stroke subtype
3.  Genetic risk factors for ischaemic stroke and its subtypes (the METASTROKE Collaboration): a meta-analysis of genome-wide association studies 
Traylor, Matthew | Farrall, Martin | Holliday, Elizabeth G | Sudlow, Cathie | Hopewell, Jemma C | Cheng, Yu-Ching | Fornage, Myriam | Ikram, M Arfan | Malik, Rainer | Bevan, Steve | Thorsteinsdottir, Unnur | Nalls, Mike A | Longstreth, WT | Wiggins, Kerri L | Yadav, Sunaina | Parati, Eugenio A | DeStefano, Anita L | Worrall, Bradford B | Kittner, Steven J | Khan, Muhammad Saleem | Reiner, Alex P | Helgadottir, Anna | Achterberg, Sefanja | Fernandez-Cadenas, Israel | Abboud, Sherine | Schmidt, Reinhold | Walters, Matthew | Chen, Wei-Min | Ringelstein, E Bernd | O'Donnell, Martin | Ho, Weang Kee | Pera, Joanna | Lemmens, Robin | Norrving, Bo | Higgins, Peter | Benn, Marianne | Sale, Michele | Kuhlenbäumer, Gregor | Doney, Alexander S F | Vicente, Astrid M | Delavaran, Hossein | Algra, Ale | Davies, Gail | Oliveira, Sofia A | Palmer, Colin N A | Deary, Ian | Schmidt, Helena | Pandolfo, Massimo | Montaner, Joan | Carty, Cara | de Bakker, Paul I W | Kostulas, Konstantinos | Ferro, Jose M | van Zuydam, Natalie R | Valdimarsson, Einar | Nordestgaard, Børge G | Lindgren, Arne | Thijs, Vincent | Slowik, Agnieszka | Saleheen, Danish | Paré, Guillaume | Berger, Klaus | Thorleifsson, Gudmar | Hofman, Albert | Mosley, Thomas H | Mitchell, Braxton D | Furie, Karen | Clarke, Robert | Levi, Christopher | Seshadri, Sudha | Gschwendtner, Andreas | Boncoraglio, Giorgio B | Sharma, Pankaj | Bis, Joshua C | Gretarsdottir, Solveig | Psaty, Bruce M | Rothwell, Peter M | Rosand, Jonathan | Meschia, James F | Stefansson, Kari | Dichgans, Martin | Markus, Hugh S
Lancet Neurology  2012;11(11):951-962.
Various genome-wide association studies (GWAS) have been done in ischaemic stroke, identifying a few loci associated with the disease, but sample sizes have been 3500 cases or less. We established the METASTROKE collaboration with the aim of validating associations from previous GWAS and identifying novel genetic associations through meta-analysis of GWAS datasets for ischaemic stroke and its subtypes.
We meta-analysed data from 15 ischaemic stroke cohorts with a total of 12 389 individuals with ischaemic stroke and 62 004 controls, all of European ancestry. For the associations reaching genome-wide significance in METASTROKE, we did a further analysis, conditioning on the lead single nucleotide polymorphism in every associated region. Replication of novel suggestive signals was done in 13 347 cases and 29 083 controls.
We verified previous associations for cardioembolic stroke near PITX2 (p=2·8×10−16) and ZFHX3 (p=2·28×10−8), and for large-vessel stroke at a 9p21 locus (p=3·32×10−5) and HDAC9 (p=2·03×10−12). Additionally, we verified that all associations were subtype specific. Conditional analysis in the three regions for which the associations reached genome-wide significance (PITX2, ZFHX3, and HDAC9) indicated that all the signal in each region could be attributed to one risk haplotype. We also identified 12 potentially novel loci at p<5×10−6. However, we were unable to replicate any of these novel associations in the replication cohort.
Our results show that, although genetic variants can be detected in patients with ischaemic stroke when compared with controls, all associations we were able to confirm are specific to a stroke subtype. This finding has two implications. First, to maximise success of genetic studies in ischaemic stroke, detailed stroke subtyping is required. Second, different genetic pathophysiological mechanisms seem to be associated with different stroke subtypes.
Wellcome Trust, UK Medical Research Council (MRC), Australian National and Medical Health Research Council, National Institutes of Health (NIH) including National Heart, Lung and Blood Institute (NHLBI), the National Institute on Aging (NIA), the National Human Genome Research Institute (NHGRI), and the National Institute of Neurological Disorders and Stroke (NINDS).
PMCID: PMC3490334  PMID: 23041239
4.  The association of circulating inflammatory markers with recurrent vascular events after stroke: a prospective cohort study 
Inflammatory markers may be associated with recurrent vascular events after stroke. We aimed to: (1) determine the association between interleukin-6, C-reactive protein, fibrinogen and white cell count and recurrent vascular events after stroke, and (2) compare the association between circulating inflammatory markers and the risk of death from vascular versus non-vascular causes.
Methods and Results
We prospectively recruited patients with acute stroke (n=817) and followed them for up to 4 years for the occurrence of: fatal or non-fatal recurrent stroke, myocardial infarction or fatal vascular events, and death from any cause (n=159). The delay to assessment was a median of 10 days. The adjusted incidence of the outcome cluster ‘recurrent stroke, myocardial infarction or vascular death’ after stroke was significantly higher with higher levels of interleukin 6 (75th to 25th centile: hazard ratio [HR] 1.56, 95 % CI 1.37 to 1.77), C-reactive protein (75th to 25th centile HR 1·08, 95% CI 1·04 to 1·11) and fibrinogen (75th to 25th centile HR 1.45, 95% CI 1.24 to 1.72). The associations between inflammatory markers and death were stronger than with recurrent vascular events. The associations of inflammatory markers with vascular and non-vascular deaths were similar.
Though inflammatory markers were associated with an increased risk of recurrent vascular events and vascular death after stroke, they were also associated with non-vascular causes of death, suggesting that inflammatory markers do not play a causal role specifically in the generation of recurrent vascular events after stroke. Future studies of the prediction of recurrent vascular events after stroke should concentrate on clinical variables, or different blood markers.
PMCID: PMC3016514  PMID: 21127302
Inflammation; stroke; prognosis
6.  Improving adherence to medication in stroke survivors (IAMSS): a randomised controlled trial: study protocol 
BMC Neurology  2010;10:15.
Adherence to therapies is a primary determinant of treatment success, yet the World Health Organisation estimate that only 50% of patients who suffer from chronic diseases adhere to treatment recommendations. In a previous project, we found that 30% of stroke patients reported sub-optimal medication adherence, and this was associated with younger age, greater cognitive impairment, lower perceptions of medication benefits and higher specific concerns about medication. We now wish to pilot a brief intervention aimed at (a) helping patients establish a better medication-taking routine, and (b) eliciting and modifying any erroneous beliefs regarding their medication and their stroke.
Thirty patients will be allocated to a brief intervention (2 sessions) and 30 to treatment as usual. The primary outcome will be adherence measured over 3 months using Medication Event Monitoring System (MEMS) pill containers which electronically record openings. Secondary outcomes will include self reported adherence and blood pressure.
This study shall also assess uptake/attrition, feasibility, ease of understanding and acceptability of this complex intervention.
Trial Registration
Current Controlled Trials ISRCTN38274953
PMCID: PMC2838838  PMID: 20181255
7.  Inflammatory Markers and Poor Outcome after Stroke: A Prospective Cohort Study and Systematic Review of Interleukin-6 
PLoS Medicine  2009;6(9):e1000145.
In a prospective cohort study of patient outcomes following stroke, William Whiteley and colleagues find that markers of inflammatory response are associated with poor outcomes. However, addition of these markers to existing prognostic models does not improve outcome prediction.
The objective of this study was to determine whether: (a) markers of acute inflammation (white cell count, glucose, interleukin-6, C-reactive protein, and fibrinogen) are associated with poor outcome after stroke and (b) the addition of markers to previously validated prognostic models improves prediction of poor outcome.
Methods and Findings
We prospectively recruited patients between 2002 and 2005. Clinicians assessed patients and drew blood for inflammatory markers. Patients were followed up by postal questionnaire for poor outcome (a score of>2 on the modified Rankin Scale) and death through the General Register Office (Scotland) at 6 mo. We performed a systematic review of the literature and meta-analysis of the association between interleukin-6 and poor outcome after stroke to place our study in the context of previous research. We recruited 844 patients; mortality data were available in 844 (100%) and functional outcome in 750 (89%). After appropriate adjustment, the odds ratios for the association of markers and poor outcome (comparing the upper and the lower third) were interleukin-6, 3.1 (95% CI: 1.9–5.0); C-reactive protein, 1.9 (95% CI: 1.2–3.1); fibrinogen, 1.5 (95% CI: 1.0–2.36); white cell count, 2.1 (95% CI: 1.3–3.4); and glucose 1.3 (95% CI: 0.8–2.1). The results for interleukin-6 were similar to other studies. However, the addition of inflammatory marker levels to validated prognostic models did not materially improve model discrimination, calibration, or reclassification for prediction of poor outcome after stroke.
Raised levels of markers of the acute inflammatory response after stroke are associated with poor outcomes. However, the addition of these markers to a previously validated stroke prognostic model did not improve the prediction of poor outcome. Whether inflammatory markers are useful in prediction of recurrent stroke or other vascular events is a separate question, which requires further study.
Please see later in the article for the Editors' Summary
Editors' Summary
Every year, 15 million people have a stroke. In the US alone, someone has a stroke every 40 seconds and someone dies from a stroke every 3–4 minutes. Stroke occurs when the blood supply to the brain is suddenly interrupted by a blood clot blocking a blood vessel in the brain (ischemic stroke, the commonest type of stroke) or by a blood vessel in the brain bursting (hemorrhagic stroke). Deprived of the oxygen normally carried to them by the blood, the brain cells near the blockage die. The symptoms of stroke depend on which part of the brain is damaged but include sudden weakness or paralysis along one side of the body, vision loss in one or both eyes, and confusion or trouble speaking or understanding speech. Anyone experiencing these symptoms should seek medical assistance immediately because prompt treatment can limit the damage to the brain. Risk factors for stroke include age (three-quarters of strokes occur in people over 65 years old), high blood pressure, and heart disease.
Why Was This Study Done?
Many people are left with permanent disabilities after a stroke. An accurate way to predict the likely long-term outcome (prognosis) for individual patients would help clinicians manage their patients and help relatives and patients come to terms with their changed circumstances. Clinicians can get some idea of their patients' likely outcomes by assessing six simple clinical variables. These include the ability to lift both arms and awareness of the present situation. But could the inclusion of additional variables improve the predictive power of this simple prognostic model? There is some evidence that high levels in the blood of inflammatory markers (for example, interleukin-6 and C-reactive protein) are associated with poor outcomes after stroke—inflammation is the body's response to infection and to damage. In this prospective cohort study, the researchers investigate whether inflammatory markers are associated with poor outcome after stroke and whether the addition of these markers to the six-variable prognostic model improves its predictive power. Prospective cohort studies enroll a group of participants and follow their subsequent progress.
What Did the Researchers Do and Find?
The researchers recruited 844 patients who had had a stroke (mainly mild ischemic strokes) in Edinburgh. Each patient was assessed soon after the stroke by a clinician and blood was taken for the measurement of inflammatory markers. Six months after the stroke, the patient or their relatives completed a postal questionnaire that assessed their progress. Information about patient deaths was obtained from the General Register Office for Scotland. Dependency on others for the activities of daily life or dying was recorded as a poor outcome. In their statistical analysis of these data, the researchers found that raised levels of several inflammatory markers increased the likelihood of a poor outcome. For example, after allowing for age and other factors, individuals with interleukin-6 levels in the upper third of the measured range were three times as likely to have a poor outcome as patients with interleukin-6 levels in the bottom third of the range. A systematic search of the literature revealed that previous studies that had looked at the potential association between interleukin-6 levels and outcome after stroke had found similar results. Finally, the researchers found that the addition of inflammatory marker levels to the six-variable prognostic model did not substantially improve its ability to predict outcome after stroke for this cohort of patients.
What Do These Findings Mean?
These findings provide additional support for the idea that increased levels of inflammatory markers are associated with a poor outcome after stroke. However, because patients with infections were not excluded from the study, infection may be responsible for part of the observed association. Importantly, these findings also show that although the inclusion of inflammatory markers in the six variable prognostic model slightly improves its ability to predict outcome, the magnitude of this improvement is too small to warrant the use of these markers in routine practice. Whether the measurement of inflammatory markers might be useful in the prediction of recurrent stroke—at least a quarter of people who survive a stroke will have another one within 5 years—requires further study.
Additional Information
Please access these Web sites via the online version of this summary at
This study is further discussed in a PLoS Medicine Perspective by Len Kritharides
The US National Institute of Neurological Disorders and Stroke provides information about all aspects of stroke (in English and Spanish); the Know Stroke site provides educational materials about stroke prevention, treatment, and rehabilitation (in English and Spanish)
The Internet Stroke Center provides detailed information about stroke for patients, families and health professionals (in English and Spanish)
The UK National Health Service also provides information for patients and their families about stroke (in several languages)
MedlinePlus provides links to further resources and advice about stroke (in English and Spanish)
The six simple variable model for prediction of death or disability after stroke is available here:
PMCID: PMC2730573  PMID: 19901973
8.  Effects of apolipoprotein E genotype on outcome after ischaemic stroke, intracerebral haemorrhage and subarachnoid haemorrhage 
Rodent models of acute ischaemic stroke and head injury suggest that apolipoprotein E genotype (APOE) influences neuronal repair, regeneration and survival after brain injury. Possession of an APOE ε4 allele is associated with poor outcome after head injury in clinical studies. APOE might therefore influence outcome after acute stroke in humans.
We comprehensively sought, identified, assessed and performed meta-analyses of studies reporting on the association between APOE and the combined outcome of death or dependency, or death alone, several months after ischaemic stroke (IS), intracerebral haemorrhage (ICH) or subarachnoid haemorrhage (SAH).
Our main analyses included data from 9 studies in a total of 2262 patients (1453 IS, 199 ICH, 610 SAH). Overall, ε4+ genotypes were not significantly associated with risk of death or dependency several months after stroke. However, there was significant heterogeneity between studies, and between the three pathological types of stroke. ε4+ genotypes were associated with increased death or dependency after SAH (RR 1.40, 95% CI 1.06 to 1.84), with a trend toward a similar association with ICH (RR 1.38, 95% CI 0.99 to 1.92), but not IS (RR 0.98, 95% CI 0.85 to 1.12). Results were similar for death alone.
APOE may differentially affect outcome after the three main pathological types of stroke. Further, large studies are needed to confirm or refute these findings, and to assess the possibility of an interaction between the effects of APOE and age.
PMCID: PMC2077401  PMID: 16926234
9.  Comparing risks of death and recurrent vascular events between lacunar and non-lacunar infarction 
Brain : a journal of neurology  2005;128(Pt 11):2507-2517.
Differences in prognosis of lacunar and non-lacunar infarction patients might support distinct arterial pathological processes underlying these two subtypes of ischaemic stroke. We did a systematic review in which we identified cohort studies with ischaemic stroke subtype-specific follow-up data on death, recurrent stroke and/or myocardial infarction (MI). We calculated risks of death and recurrent stroke at 1 month, 1-12 months and 1-5 years, as well as risks of MI and cardiac death. We compared non-lacunar with lacunar infarction, using study-specific and summary odds ratios. We also compared the pattern of recurrent stroke subtypes after lacunar and non-lacunar infarction. One month odds of death and of recurrent stroke were significantly greater following non-lacunar than lacunar infarction, but the difference decreased thereafter (one month mortality: OR 3.81, 95% CI 2.77 to 5.23; 1-12 month mortality: OR 2.32, 95% CI 1.74 to 3.08; 1-5 year mortality: OR 1.77, 95% CI 1.28 to 2.45; one month stroke recurrence OR 2.11, 95% CI 1.20 to 3.69; 1-12 month stroke recurrence OR 1.24, 95% CI 0.85 to 1.83; 1-5 year stroke recurrence OR 1.61, 95% CI 0.96 to 2.70). Recurrent strokes were more likely to be lacunar if the index event was lacunar. Few studies reported on the risk of MI, but we found no significant difference in risk of cardiac death in non-lacunar versus lacunar infarction. Thus, although early mortality and stroke recurrence risk are higher among non-lacunar than lacunar infarct patients, the risks appear not to differ in the longer term and the risks of cardiac outcomes are similar, although data are limited. There is some evidence that recurrent ischaemic stroke subtypes breed true. These results provide limited support for a distinct arterial pathology underlying lacunar infarction.
PMCID: PMC2577181  PMID: 16195245
lacunar infarction; prognosis; outcome; recurrent stroke; death
10.  Does Apolipoprotein E Genotype Influence the Risk of Ischemic Stroke, Intracerebral Hemorrhage, or Subarachnoid Hemorrhage? 
Background and Purpose
Apolipoprotein E genotype (APOE) is associated with cholesterol metabolism, ischemic heart disease, and cerebral amyloid angiopathy, and so may affect risk of both ischemic and hemorrhagic stroke.
We comprehensively sought and identified studies of the association of apoE with ischemic stroke (IS), intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH). We did meta-analyses to assess the evidence for an association between APOE and the various pathological types and subtypes of stroke, and assessed the effects of several methodological criteria.
We analyzed data from 31 eligible studies (26 IS, 8 ICH, and 3 SAH) in 5961 cases and 17 965 controls. ∊4 allele-containing (∊4+) genotypes were significantly associated with IS (odds ratio [OR], 1.11; 95% CI, 1.01 to 1.22) and SAH (OR, 1.42; 95% CI, 1.01 to 1.99) and nonsignificantly with ICH (OR, 1.16; 95% CI, 0.93 to 1.44), whereas ∊2+ genotypes were associated with ICH (OR, 1.32; 95% CI, 1.01 to 1.74). Associations appeared stronger with ∊4+ genotypes for large artery compared with other IS subtypes and for Asian compared with white populations, and with ∊2+ genotypes for lobar compared with deep hemorrhages. However, we found no association between ∊4+ genotypes and IS when we analyzed only larger studies (>200 cases; OR, 0.99; 95% CI, 0.88 to 1.11) or studies without control selection bias (OR, 0.99; 95% CI, 0.85 to 1.17).
Publication and selection biases make existing studies of APOE and stroke unreliable. Further, very large, methodologically rigorous studies are needed.
PMCID: PMC2577180  PMID: 16385096
apolipoproteins E; genetics; meta-analysis; stroke
11.  Are Lacunar Strokes Really Different? 
Background and Purpose
Differences in risk factors between lacunar and nonlacunar infarcts might support a distinct arterial pathological process underlying lacunar infarction.
We did a systematic review of studies comparing risk factors in patients with lacunar versus nonlacunar infarction. For each risk factor, we calculated study-specific and pooled relative risks (RRs) for lacunar versus nonlacunar infarction.
A total of 16 of 28 studies included risk factors in their ischemic stroke subtype definitions. Hypertension and diabetes appeared commoner among patients with lacunar versus nonlacunar infarction. However, analyses confined to studies using risk factor-free ischemic subtype definitions found only a marginal excess of hypertension with lacunar versus nonlacunar infarction (RR, 1.11; 95% CI, 1.04 to 1.19) and no difference for diabetes (RR, 0.95; 95% CI, 0.83 to 1.09). Atrial fibrillation and carotid stenosis were associated more with nonlacunar than lacunar infarction but less so when only studies using risk factor-free classifications were considered. Otherwise, there was no evidence of differences in risk factor profiles.
Risk factor-free ischemic stroke subtype classification methods should be used for comparing risk factor profiles between lacunar and nonlacunar subtypes.
PMCID: PMC2577185  PMID: 15761206
lacunar infarction; meta-analysis; risk factors; stroke
12.  Association Between Apolipoprotein E Genotype and Carotid Intima-Media Thickness May Suggest a Specific Effect on Large Artery Atherothrombotic Stroke 
Background and Purpose
Apolipoprotein E genotype (APOE) influences cholesterol levels and ischemic heart disease. Although there is no convincing overall association with ischemic stroke, APOE may influence large artery (atherothrombotic) stroke, for which carotid intima-media thickness (CIMT) is an informative intermediate phenotype. We therefore performed a systematic review and meta-analysis of the association between APOE and CIMT.
We sought all published studies assessing the association between APOE and CIMT. From each study, we extracted available data on study methods, subjects’ characteristics, and mean (and standard deviation) CIMT for each genotype or genotype group. We calculated study-specific and random effects pooled differences in mean CIMT between genotype groups, and assessed heterogeneity between studies and predefined subgroups using I2 and χ2 statistics.
Meta-analysis of 22 published studies (30 879 subjects) showed a significant association between APOE and CIMT (pooled mean difference ε4-versus ε2-allele containing genotypes 46 μm, 95% CI 29 to 62, P<0.00001). We found evidence of small study (mainly publication) bias, with a diminished (but still highly statistically significant) association in studies of >1000 subjects (pooled mean difference 17 μm, 95% CI 12 to 23, P<0.00001). The association was larger among high vascular risk and eastern Asian populations, but this may simply reflect the smaller size of these studies.
Our results show a clear association of APOE with CIMT, even though publication bias means that this is overestimated by the published literature. These findings suggest the possibility of a specific association with large artery ischemic stroke.
PMCID: PMC2577179  PMID: 18063831
apolipoprotein E; association; carotid intimal medial thickness; genetics; meta-analysis
13.  Assessing the impact of the requirement for explicit consent in a hospital-based stroke study 
Increasing regulation of medical research, in particular the requirement for explicit consent, may reduce the quantity and quality of clinical epidemiological research.
To assess the potential biases arising from the need for explicit consent in our hospital-based stroke research register.
Comparison of patients enrolled into our stroke research register with those included in a concurrent clinical stroke audit that targeted the same population but did not require explicit consent.
We obtained the numbers of consenters, refusers, and those from whom consent was not sought for various logistical reasons. We compared characteristics of participants (those eventually included in the research register) versus non-participants.
Of 1228 patients included in the stroke audit during an 18-month period, 1075 (88%) were also included in the research register, with higher participation among outpatients than inpatients. Only 1% of eligible patients refused involvement in any aspect of the research register. By far the largest number of non-participants was those from whom we could not seek consent for practical reasons. Comparison of baseline characteristics showed important differences between participants and non-participants that could affect outcome.
Very few patients refused inclusion in our research register, but the need for explicit consent reduced participation and introduced bias. An opt-out system avoiding the need for explicit patient consent for minimally intrusive clinical epidemiological studies would minimise bias and reduce the considerable time and costs associated with the consent process.
PMCID: PMC2569699  PMID: 18281363
15.  Survival after stroke in south London 
BMJ : British Medical Journal  2005;331(7514):414-415.
PMCID: PMC1188096  PMID: 16110054
19.  Ischemic Stroke Is Associated with the ABO Locus: The EuroCLOT Study 
Annals of Neurology  2013;73(1):16-31.
End-stage coagulation and the structure/function of fibrin are implicated in the pathogenesis of ischemic stroke. We explored whether genetic variants associated with end-stage coagulation in healthy REFVIDunteers account for the genetic predisposition to ischemic stroke and examined their influence on stroke subtype.
Common genetic variants identified through genome-wide association studies of coagulation factors and fibrin structure/function in healthy twins (n = 2,100, Stage 1) were examined in ischemic stroke (n = 4,200 cases) using 2 independent samples of European ancestry (Stage 2). A third clinical collection having stroke subtyping (total 8,900 cases, 55,000 controls) was used for replication (Stage 3).
Stage 1 identified 524 single nucleotide polymorphisms (SNPs) from 23 linkage disequilibrium blocks having significant association (p < 5 × 10–8) with 1 or more coagulation/fibrin phenotypes. The most striking associations included SNP rs5985 with factor XIII activity (p = 2.6 × 10–186), rs10665 with FVII (p = 2.4 × 10–47), and rs505922 in the ABO gene with both von Willebrand factor (p = 4.7 × 10–57) and factor VIII (p = 1.2 × 10–36). In Stage 2, the 23 independent SNPs were examined in stroke cases/noncases using MOnica Risk, Genetics, Archiving and Monograph (MORGAM) and Wellcome Trust Case Control Consortium 2 collections. SNP rs505922 was nominally associated with ischemic stroke (odds ratio = 0.94, 95% confidence interval = 0.88–0.99, p = 0.023). Independent replication in Meta-Stroke confirmed the rs505922 association with stroke, beta (standard error, SE) = 0.066 (0.02), p = 0.001, a finding specific to large-vessel and cardioembolic stroke (p = 0.001 and p = < 0.001, respectively) but not seen with small-vessel stroke (p = 0.811).
ABO gene variants are associated with large-vessel and cardioembolic stroke but not small-vessel disease. This work sheds light on the different pathogenic mechanisms underpinning stroke subtype. Ann Neurol 2013
PMCID: PMC3582024  PMID: 23381943

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