Differences in vascular risk factors between etiological subtypes of ischemic stroke: importance of population-based studies

Lipoprotein (a) and risk of ischemic stroke in young adults

Lipoprotein (a) [Lp(a)] is a LDL-particle linked to apoprotein (a) [apo(a)]. High Lp(a) plasma level is a risk factor for coronary heart disease and, in older men, for ischemic stroke. The role of Lp(a) as a risk factor for ischemic stroke in young adults is uncertain.

METHODS

Lp(a) concentration was prospectively measured in 100 consecutive patients with acute ischemic stroke (58 men and 42 women) aged 18-55 years, and in 100 controls matched for age and gender.

RESULTS

The distribution of Lp(a) concentration was skewed toward the highest and median tertiles in male patients. In multivariate logistic regression analyses adjusting on classical risk factors for ischemic stroke and lipid variables, Lp(a) concentration in the highest and medium tertiles compared with the lowest tertile was significantly associated with ischemic stroke in men (OR 3.55, 95% CI 1.33-9.48, p = 0.012), but was not in women (OR 0.42, 95% CI 0.14-1.26, p = 0.12). Although large vessel atherosclerosis was more common in men than in women, there were no differences in Lp(a) concentration according to the cause of ischemic stroke.

CONCLUSION

Among subjects aged 18-55 years, a slightly elevated Lp(a) concentration was strongly and independently associated with ischemic stroke in men, but not in women. Further studies are required to elucidate the mechanisms underlying this gender-specific association.

Different risk factor profiles between subtypes of ischemic stroke. A case-control study in Korean men

Ischemic stroke is composed of subtypes with variable underlying pathogenesis and studies on ischemic stroke as a whole may inadequately evaluate risk factors, being influenced by subtype distribution among studied population. This study aimed to evaluate risk factors associated with individual ischemic stroke subtypes defined by the Trial of ORG10172 in Acute Stroke Treatment. In a case-control study (290 first-ever ischemic stroke cases and 1160 individually matched controls without stroke) nested within Korean male public servants cohort, a range of potential risk factors measured at periodic health surveys prior to the onset of stroke event were examined using conditional logistic regression analysis. Increased risk for large-artery atherosclerosis was associated with hypercholesterolemia (> or = 6.2 mmol/L), hypertension, and smoking. Increased risk for small-artery occlusion was associated with hypertension, hyperglycemia (> or = 7.0 mmol/L), and frequent alcohol intake. No specific risk factor was identified for cardioembolism. For combined ischemic stroke, hypercholesterolemia, hyperglycemia, hypertension, and smoking were associated with the increased risk, but the relative odds were much smaller than those estimated from subtype analysis. Significance of risk factors evaluated for subtypes, rather than ischemic stroke as a whole, should be reflected in preventive efforts against the burden of ischemic stroke.

Ethnic Variations in Risk Factor Profile, Pattern and Recurrence of Non-Cardioembolic Ischemic Stroke

BACKGROUND

Ischemic stroke is influenced by ethnic and geographical variations. The aim of this study was to identify the risk factor profiles, subtypes and recurrence of non-cardioembolic ischemic stroke for the two largest subpopulations, the Arab and South Asians, at the only stroke-admitting hospital in Qatar.

METHODS

Data on stroke patients admitted to Hamad Medical Corporation from January through December 2001 were reviewed in January 2005. Only patients with non-cardioembolic ischemic stroke and complete work-up were included.

RESULTS

A total of 303 patients with ischemic non-cardioembolic stroke fit the entry criteria. Sixty seven percent of the overall patient population (sex ratio 2:6, M/F) was of Arab origin, and 32% were South Asians. Hypertension was the most commonly encountered risk factor followed by dyslipidemia, diabetes mellitus, and obesity. Significant differences between the Arab and South Asian subgroup of patients were observed with respect to number of risk factors and occurrence of obesity and diabetes. Carotid artery stenotic lesions, ventricular wall motion abnormalities and stroke recurrence were observed with a higher frequency in the Arab subgroup of patients compared with the South Asians. The majority of strokes were lacunar hemispheric strokes (68%), followed by lacunar brainstem strokes (15%) and large-vessel hemispheric infarctions (10%). Patients with a previous history of stroke had a higher frequency of carotid artery stenosis (p = 0.05) and risk of stroke recurrence (p = 0.04).

CONCLUSIONS

Unlike in other studies originating from the Arabian Gulf, lacunar stroke is the most common subtype of non-cardioembolic ischemic stroke in both the Arabs and South Asians in Qatar. Significant ethnic differences in age of occurrence, risk factor profile, and cardiovascular variables were observed.

Potential new risk factors for ischemic stroke: what is their potential?

BACKGROUND AND PURPOSE

About 60% to 80% of all ischemic strokes can be attributed to increasing blood pressure, blood cholesterol, cigarette smoking, carotid stenosis, and diabetes mellitus (atherosclerotic ischemic stroke), and atrial fibrillation and valvular heart disease (cardiogenic ischemic stroke). The aim of this review was to examine the potential role of other risk factors in the etiology of ischemic stroke.

SUMMARY OF REVIEW

About 10% to 20% of atherosclerotic ischemic strokes can probably be attributed to recently established, causal risk factors for ischemic heart disease: raised apoB/apoA 1 ratio, obesity, physical inactivity, pyschosocial stress and low fruit and vegetable intake. However, their causal role remains to be proven. The direct genetic contribution of any single gene towards ischemic stroke is likely to be modest and apply in selected patients only and in combination with environmental factors or via other epistatic (gene-gene or gene-environmental) effects.

CONCLUSIONS

Research resources should not be allocated disproportionately to emerging novel risk factors that may account for up to only 20% of all strokes at the expense of researching the determinants of the relatively few established causal factors that account for up to 80% of all strokes.

Risk factors and outcome of subtypes of ischemic stroke. Data from a multicenter multinational hospital-based registry. The European Community Stroke Project

BACKGROUND

Information on determinants and prognosis of ischemic stroke subtypes is scarce. We aimed at evaluating risk factors, pathogenesis, treatment and outcome of different ischemic stroke subtypes.

METHODS

In a European Concerted Action involving seven countries, ischemic stroke subtypes defined according to the Oxfordshire Community Stroke Project (OCSP) were evaluated for demographics, baseline risk factors, resource use, 3-month survival, disability (Barthel Index) and handicap (Rankin Scale).

RESULTS

During the 12-month study period, cerebral infarction was diagnosed in 2740 patients with first-in-a-lifetime stroke (mean age 70.5+/-12.4 years, 53.4% males). OCSP classification was achieved in 2472 (90.2%). Of these, 26.7% were total anterior circulation infarctions (TACI), 29.9% partial anterior circulation infarctions (PACI), 16.7% posterior circulation infarctions (POCI) and 26.7% lacunar infarctions (LACI). In multivariate analysis, atrial fibrillation was predictive of TACI (odds ratio [OR], 1.61; 95% CI, 1.28-2.03), hypertension (OR, 1.38; 95% CI, 1.16-1.65) and myocardial infarction (OR, 1.42; 95% CI, 1.08-1.86) predictive of PACI, hypertension (OR, 1.25; 95% CI, 1.04-1.50) predictive of LACI. A negative association was observed between TACI and hypertension (OR, 0.51; 95% CI, 0.42-0.61). Discharge home was 50% less probable in TACI and PACI than in LACI patients. As compared to LACI, TACI significantly increased the risk of 3-month death (OR, 5.73; 95% CI, 3.91-8.41), disability (OR, 3.27; 95% CI, 2.30-4.66) and handicap (OR, 2.71; 95% CI, 1.91-3.85).

CONCLUSIONS

Ischemic stroke subtypes have different risk factors profile, with consequences on pathogenesis and prognosis. Information on determinants of the clinical syndromes may impact on prevention and acute-phase interventions.

Ethnic disparities in incidence of stroke subtypes: Auckland Regional Community Stroke Study, 2002–2003

BACKGROUND

Limited population-based data exist on differences in the incidence of major pathological stroke types and ischaemic stroke subtypes across ethnic groups. We aimed to provide such data within the large multi-ethnic population of Auckland, New Zealand.

METHODS

All first-ever cases of stroke (n=1423) in a population-based register in 940 000 residents (aged 15 years) in Auckland, New Zealand, for a 12-month period in 2002-2003, were classified into ischaemic stroke, primary intracerebral haemorrhage (PICH), subarachnoid haemorrhage, and undetermined stroke, according to standard definitions and results of neuroimaging/necropsy (in over 90% of cases). Ischaemic stroke was further classified into five subtypes. Ethnicity was self-identified and grouped as New Zealand (NZ)/European, Maori/Pacific, and Asian/other. Incidence rates were standardised to the WHO world population by the direct method, and differences in rates between ethnic groups expressed as rate ratios (RRs), with NZ/European as the reference group.

FINDINGS

In NZ/European people, ischaemic stroke comprised 73%, PICH 11%, and subarachnoid haemorrhage 6%, but PICH was higher in Maori/Pacific people (17%) and in Asian/other people (22%). Compared with NZ/European people, age-adjusted RRs for PICH were 2.7 (95% CI 1.8-4.0) and 2.3 (95% CI 1.4-3.7) among Maori/Pacific and Asian/other people, respectively. The corresponding RR for ischaemic stroke was greater for Maori/Pacific people (1.7 [95% CI 1.4-2.0]), particularly embolic stroke, and for Asian/other people (1.3 [95% CI 1.0-1.7]). The onset of stroke in Maori/Pacific and Asian/other people began at significantly younger ages (62 years and 64 years, respectively) than in NZ/Europeans (75 years; p<0.0001). There were ethnic differences in the risk factor profiles (such as age, sex, hypertension, cardiac disease, diabetes, hypercholesterolaemia, smoking status, overweight) for the stroke types and subtypes.

INTERPRETATION

Compared to NZ/Europeans, Maori/Pacific and Asian/other people are at higher risk of ischaemic stroke and PICH, whereas similar rates of subarachnoid haemorrhage were evident across ethnic groups. The ethnic disparities in the rates of stroke types could be due to substantial differences found in risk factor profiles between ethnic groups. This information should be considered when planning prevention and stroke-care services in multi-ethnic communities.

Arterial hypertension as risk factor for spontaneous cervical artery dissection. A case-control study

Because of the presumed non-atherosclerotic pathogenesis, the potential link between spontaneous cervical artery dissection (sCAD) and common risk factors for atherosclerosis has never been investigated systematically. Therefore, this prospective, multicentre, case-control study compared the frequency of tobacco use, hypertension, diabetes mellitus, and hypercholesterolaemia among a group of consecutive patients with sCAD (n = 153), a group of patients with ischaemic stroke, not related to CAD (non-CAD), and a group of controls. As opposed to the other variables, a trend towards a significant association was seen when the prevalence of hypertension was compared among patients with sCAD and controls (26.8% v 17.0%; odds ratio (OR) 1.79; 95% confidence interval (CI), 0.98 to 3.27; p = 0.058). Hypertension was also significantly associated with the subgroup of patients with sCAD and cerebral infarction (OR, 1.94; 95% CI, 1.01 to 3.70; p = 0.045), particularly when involving the vertebral arteries (OR, 2.69; 95% CI, 1.20 to 6.04; p = 0.017). These findings might help define the spectrum of pathogenic conditions predisposing to sCAD and provide information to help investigate the combined effect of such susceptibility factors in future studies.

Trends in Ethnic Disparities in Stroke Incidence in Auckland, New Zealand, During 1981 to 2003

Background and Purpose— Although geographical variations in stroke rates are well documented, limited data exist on temporal trends in ethnic-specific stroke incidence.

Methods— We assessed trends in ethnic-specific stroke rates using standard diagnostic criteria and community-wide surveillance procedures in Auckland, New Zealand (NZ) in 1981 to 1982, 1991 to 1992, and 2002 to 2003. Indirect and direct methods were used to adjust first-ever (incident) and total (attack) rates for changes in the structure of the population and reported with 95% CIs. Ethnicity was self-defined and categorized as “NZ/European,” “Maori,” “Pacific peoples,” and “Asian and other.”

Results— Stroke attack (19%; 95% CI, 11% to 26%) and incidence rates (19%; 95% CI, 12% to 24%) declined significantly in NZ/Europeans from 1981 to 1982 to 2002 to 2003. These rates remained high or increased in other ethnic groups, particularly for Pacific peoples in whom stroke attack rates increased by 66% (95% CI; 11% to 225%) over the periods. Some favorable downward trends in vascular risk factors, such as cigarette smoking, were counterbalanced by increasing age, body mass index, and diabetes in certain ethnic groups.

Conclusions— Divergent trends in ethnic-specific stroke incidence and attack rates, and of associated risk factors, have occurred in Auckland over recent decades. The findings provide mixed views as to the future burden of stroke in populations undergoing similar lifestyle and structural changes.

Lymphotoxin-alpha gene 252G allelic variant is a risk factor for large-vessel-associated ischemic stroke

A direct role of lymphotoxin-alpha (LTA) in promoting atherosclerotic plaque growth has been demonstrated recently. The different protein transcripts of the naturally occurring genetic variants of the LTA gene have been demonstrated to exhibit affected functions, and an allelic difference in binding to transcription factor(s) has also been suggested. The homozygous variant of LTA characterized by the intron 1 252A-->G (252G) transition, which naturally coexists with an exon 3 804C-->A (804A) single-nucleotide polymorphism (SNP), has been reported as a susceptibility gene for myocardial infarction. Because the atherosclerotic process is also an integral component in the pathogenesis of certain types of vascular stroke, we investigated the possible significance of the above SNPs in 353 ischemic stroke patients and 180 healthy controls. The homozygous LTA allele with the 252G and 804C SNPs occurred more frequently in stroke patients (13.9%) than in controls (7.20%, p<0.025). Specific subclassification of the patients revealed an accumulation of these SNPs in large-vessel, pathology-associated cerebral infarction (18.2%); multivariate logistic regression analysis of the data confirmed this association, with an odds ratio of 2.1 (95% confidence interval, 1.3-6.2; p<0.005). Elimination of all subjects with a history or evidence of ischemic heart disease, including myocardial infarction, did not affect this association. These data show that besides the role in the development of myocardial infarction, the homozygous carriage of the LTA allele with 252G and 804A SNPs is a novel susceptibility factor for largevesselassociated ischemic stroke.

A Systematic Comparison of the Quality and Volume of Published Data Available on Novel Risk Factors for Stroke versus Coronary Heart Disease

BACKGROUND

To identify new treatments to prevent stroke, it is important that we have reliable data on potential novel risk factors.

METHODS

We studied seven novel vascular risk factors [apo-lipoprotein (b), C-reactive protein, Chlamydia pneumoniae, fibrin-D dimer, fibrinogen, Helicobacter pylori and lipoprotein (a)] and compared the amount of published data on their relations with ischaemic stroke versus acute coronary events by systematic review of all studies published up to 2003.

RESULTS

From a total of 22,875 abstracts reviewed, 266 eligible studies were identified (167 case-control studies and 99 cohort studies). Two hundred and eleven (79%) studies included coronary events as an outcome for the purpose of a risk factor analysis. In 186 (70%) studies, coronary events were the only outcome that was analysed. Only 73 (27%) studies included stroke or TIA as an outcome event, and only 45 studies (17%) reported risk factor analyses for ischaemic stroke separately. These results were qualitatively consistent across the risk factors studied and the relative lack of data on risk factors for stroke was even greater in prospective cohort studies.

CONCLUSION

Data on novel risk factors for stroke are lacking compared with the equivalent data for acute coronary events, and there are very few data on specific subtypes of ischaemic stroke.

Metabolic syndrome as a predictor of ischemic stroke in elderly persons

OBJECTIVE

To estimate the prevalence and risk of ischemic stroke associated with metabolic syndrome.

METHODS AND PATIENTS

In 197 stroke patients (80 cases of atherothrombotic infarction, 97 lacunar infarction, 16 cardioembolic infarction, 4 others) and 356 age- and sex-matched control subjects aged 65 years and older in Seiyo Municipal Nomura Hospital, we investigated the association between metabolic syndrome and risk factor-dependent augmentation of ischemic stroke in subjects with several risk factors for atherosclerosis. The diagnosis of cerebral infarction in each patient was confirmed by CT findings of the brain and metabolic syndrome was defined as at least 3 of the 5 following conditions: visceral obesity, hypertension (HT), hypertriglyceridemia, low HDL-cholesterol and diabetes mellitus (DM).

RESULTS

After adjustment for sex, age, and smoking, metabolic syndrome was significantly related to atherothrombotic infarction (odds ratio, 3.08; 95% confidence interval, 1.69-5.61). Of the individual components, visceral obesity, HT and DM were independent risk factors for atherothrombotic infarction. Increased risk for atherothrombotic infarction was also associated with increases in the 5 component conditions of the metabolic syndrome.

CONCLUSION

The clustering of cardiovascular risk factors called metabolic syndrome increases the risk of cardiovascular morbidity, and its identification may thus be important in risk assessment and treatment of patients.

Interleukin 1 beta polymorphism (-511) and risk of stroke due to small vessel disease

BACKGROUND

Interleukin 1 (IL-1) is a proinflammatory cytokine involved in atherogenesis and thrombosis. The aim of this study was to investigate the association between the IL-1beta gene polymorphism (-511) and the risk of large vessel disease (LVD) stroke, small vessel disease (SVD) stroke and cardioembolic (CE) stroke.

METHODS

We genotyped 115 patients with LVD stroke and 194 matched controls, 122 patients with SVD stroke and 227 controls and 221 patients with CE stroke and 219 controls. The IL-1beta polymorphism was analyzed by a polymerase chain reaction followed by a restriction enzyme digestion.

RESULTS

The allele T distribution did not change significantly between patients with LVD stroke and their controls nor between patients with CE stroke and their controls. The frequency of the T allele was higher in patients with SVD stroke than in the control group (37.7 vs. 30.4%, p = 0.05). After adjustment for vascular risk factor, the TT genotype was an independent risk factor for SVD stroke (OR: 2.40, 95% CI: 1.17-4.94).

CONCLUSIONS

The TT genotype of the IL-1beta gene may be associated with an increased risk of SVD stroke.

Family History in Ischemic Stroke Before 70 Years of Age

Background and Purpose— Results from twin and family history studies of ischemic stroke suggest that future molecular genetic studies should focus on strictly defined stroke subtypes and younger cases. Accordingly, we investigated stroke subtypes, vascular risk factors, and family history in a large study of patients with ischemic stroke onset before age 70 years.

Methods— Six hundred consecutive white participants with ischemic stroke (18 to 69 years) and 600 age- and sex-matched controls were examined for vascular risk factors and family history of stroke and myocardial infarction (MI). Stroke subtype was defined using Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria.

Results— Family history of stroke was associated with overall ischemic stroke (multivariate odds ratio [OR], 1.75; 95% confidence interval [CI], 1.26 to 2.43), large-vessel disease (LVD) (OR, 1.88; 95% CI, 1.02 to 3.44), small-vessel disease (SVD, OR, 1.79; 95% CI, 1.13 to 2.84), and cryptogenic stroke (OR, 1.70; 95% CI, 1.13 to 2.56), but not with cardioembolic stroke. Family history of MI was strongly associated with LVD (OR, 3.25; 95% CI, 1.74 to 6.07), whereas no significant association were observed for other subtypes. We also found an independent association between family history of stroke and a favorable outcome after 3 months.

Conclusion— Family history of stroke is an independent risk factor for ischemic stroke with onset before age 70 years. For the first time to our knowledge, we report this association not only for LVD and SVD but also for cryptogenic stroke, implying that future studies of the genetics of ischemic stroke should target these 3 subtypes.

Incidence, 30-day case-fatality rate, and prognosis of stroke in Iquique, Chile: a 2-year community-based prospective study (PISCIS project)

BACKGROUND

The epidemiology of stroke in Latin-American populations and variation of subtypes between communities are unclear. Our aim was to ascertain prospectively the incidence of first-ever stroke in the predominantly Hispanic-Mestizo population of Iquique, a city in the northern desert region of Chile.

METHODS

We prospectively identified all possible cases of stroke and transient ischaemic attacks between July 1, 2000, and June 30, 2002, from several overlapping sources. Patients were rapidly assessed by two field neurologists. Standard definitions for incident cases, stroke, transient ischaemic attack, pathological type, and infarction subtype were used. All cases identified were adjudicated by at least two stroke neurologists and followed up at 6 months. Incidence rates of first-ever strokes were calculated from the population of Iquique (214 526) according to the national census of 2002.

FINDINGS

Of 380 cases of stroke identified, 292 were incident. CT scans were done in 267 (91%) patients and the mean time to scan was 2.2 days. The hospital admission rate was 71% (207/292). The overall age-adjusted incidence rate of first-ever stroke was 140.1 per 100,000 (95% CI 124.0-156.2). The incidence rates per 100,000 according to pathological type were: infarcts 87.3, intracerebral haemorrhage 27.6, and subarachnoid haemorrhage 6.2. The 30 day and 6-month case-fatality rates were 23.3% and 33.0%, respectively.

INTERPRETATION

Our results show incidence rates of stroke similar to those reported in other community studies. Although the proportion of intracerebral haemorrhages was higher than reported in previous studies, the overall incidence was not, which could indicate a slightly lower incidence of ischaemic strokes in this population than in other countries. The prognosis was similar to that found in other population-based studies.

Are lacunar strokes really different? A systematic review of differences in risk factor profiles between lacunar and nonlacunar infarcts

BACKGROUND AND PURPOSE

Differences in risk factors between lacunar and nonlacunar infarcts might support a distinct arterial pathological process underlying lacunar infarction.

METHODS

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.

RESULTS

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.

CONCLUSIONS

Risk factor-free ischemic stroke subtype classification methods should be used for comparing risk factor profiles between lacunar and nonlacunar subtypes.

Potential Confounding by Intermediate Phenotypes in Studies of the Genetics of Ischaemic Stroke

BACKGROUND

Family history (FHx) of stroke is perceived to be an important risk factor for ischaemic stroke. However, there are several intermediate phenotypes that are often involved in the aetiology of ischaemic stroke and that have a substantial genetic component themselves. We studied FHx of ischaemic heart disease (IHD), hypertension (HTN) and diabetes mellitus (DM) as risk factors for ischaemic stroke.

METHODS

We performed a systematic review of case-control and cohort studies reporting on FHx(IHD), FHx(HTN) or FHx(DM) as risk factors for stroke using bibliographic databases, and by hand searching reference lists and journals. Odds ratios of FHx as a risk factor for stroke were calculated within individual studies. We included unpublished data from two Oxfordshire population-based studies to assess effects on subtypes of ischaemic stroke.

RESULTS

We identified 54 studies that investigated the odds of stroke conferred by a positive FHx, 24 of which reported data on FHx of one or more intermediate phenotypes in addition to FHx of stroke. Most studies reported an increased frequency of FHx(IHD) and FHx(HTN) in stroke patients versus controls. The association was significant in 6 out of 14 studies for FHx(IHD) and 4 out of 11 studies for FHx(HTN). In contrast, FHx(DM) was not associated with stroke. FHx(IHD) was particularly associated with large vessel strokes (OR 1.72, CI 1.3-2.2, p = 0.00004).

CONCLUSIONS

FHx(IHD) and FHx(HTN) are both risk factors for stroke. It is likely that the apparent heritability of stroke is partly accounted for by heritability of HTN and large vessel atherosclerosis. Analyses of heritability of stroke and candidate gene studies should be adjusted accordingly.

An evidence-based causative classification system for acute ischemic stroke

Regular, evidence-based assignment of patients to etiologic stroke categories is essential to enable valid comparison among studies. We designed an algorithm (SSS-TOAST) that incorporated recent advances in stroke imaging and epidemiology to identify the most probable TOAST category in the presence of evidence for multiple mechanisms. Based on the weight of evidence, each TOAST subtype was subdivided into 3 subcategories as "evident", "probable", or "possible". Classification into the subcategories was determined via predefined specific clinical and imaging criteria. These criteria included published risks of ischemic stroke from various mechanisms and published reports of the strength of associations between clinical and imaging features and particular stroke mechanisms. Two neurologists independently assessed 50 consecutively admitted patients with acute ischemic stroke through reviews of abstracted data from medical records. The number of patients classified as "undetermined-unclassified" per the original TOAST system decreased from 38-40% to 4% using the SSS-TOAST system. The kappa value for inter-examiner reliability was 0.78 and 0.90 for the original TOAST and SSS-TOAST respectively. The SSS-TOAST system successfully classifies patients with acute ischemic stroke into determined etiologic categories without sacrificing reliability. The SSS-TOAST is a dynamic algorithm that can accommodate modifications as new epidemiological data accumulate and diagnostic techniques advance.

Prevention of Stroke in Patients with Diabetes mellitus and the Metabolic Syndrome

The basic principles of stroke prevention are the same in patients with diabetes and/or the metabolic syndrome as in those without. Blood-pressure lowering is highly effective in both primary and secondary prevention of stroke in diabetics, and there is no evidence to suggest that the benefits of lipid-lowering therapy are any less. Antiplatelet agents are effective in secondary prevention and may be indicated in asymptomatic diabetic patients, who have a substantially increased risk of acute vascular events. Uncertainty over optimal management of patients with diabetes, and possibly of those with metabolic syndrome, relates more to the thresholds for initiation of treatment. The decision to initiate treatment should depend on the balance between the absolute risk of potentially preventable events and the risks of any complications of treatment. The absolute risks of ischaemic stroke and acute coronary events are significantly increased in diabetics in population-based cohort studies and the recommended thresholds for instigating blood pressure lowering and lipid lowering are therefore lower than in the general population. Optimization of strategies to prevent vascular complications must be a priority, given the rapid rises in the incidence and prevalence of type 2 diabetes and the metabolic syndrome in most populations across the globe.

A2 Alelle of GpIIIa Gene Is a Risk Factor for Stroke Caused by Large-Vessel Disease in Males

Background and Purpose— Glycoprotein IIIa (GpIIIa) is a platelet membrane receptor for fibrinogen and von Willebrand factor. It plays a key role in platelet aggregation. Previous studies in stroke patients, without analysis based on specific subtypes of stroke cause, have not shown any link between GpIIIa A1/A2 polymorphism and stroke risk. We studied the significance of the GpIIIa gene A1/A2 polymorphism in stroke patients with different stroke causes.

Methods— We genotyped 92 patients with stroke caused by large-vessel disease (LVD stroke) and 184 matched controls; 103 patients with stroke caused by small-vessel disease (SVD stroke) and 206 controls; and 182 patients with cardioembolic stroke (CE stroke) and 182 controls (TOAST criteria). The GpIIIa A1/A2 polymorphism was analyzed by polymerase chain reaction followed by restriction enzyme digestion and electrophoresis.

Results— The genotype distribution of the GpIIIa gene in patients with LVD stroke (A1/A1, 63%; A1/A2, 34.8%; A2/A2, 2.2%) differed significantly from their controls (A1A1, 79.3%; A1/A2, 20.1%; A2/A2, 0.6%). The distribution of the GpIIIa A1/A2 polymorphism in patients with SVD stroke and CE stroke was similar to that of their controls. In contrast to females with LVD stroke, we found that males with LVD stroke presented with an overrepresentation of at least 1 A2 allele of the GpIIIa gene when compared with their controls (39.7% versus 23.0%; P =0.003). Conditional logistic regression analysis showed that possession of at least 1 A2 allele of the GpIIIa gene was an independent risk factor for LVD stroke in males (OR, 2.51; 95% CI, 1.21 to 5.20).

Conclusion— A2 allele of the GpIIIa gene is an independent risk factor for LVD stroke in males.

Heritability of Ischemic Stroke in Relation to Age, Vascular Risk Factors, and Subtypes of Incident Stroke in Population-Based Studies

Background— Appropriate design of molecular genetic studies of ischemic stroke requires an understanding of the genetic epidemiology of stroke. However, there are no published population-based data on heritability of aetiological subtypes of ischemic stroke, confounding by heritability of other vascular risk factors, or the relationship between heritability and age of onset.

Methods— We studied family history of stroke (FHx Stroke ) and of myocardial infarction (FHx MI ) in first-degree relatives in 2 population-based studies (Oxford Vascular Study [OXVASC]; Oxfordshire Community Stroke Project [OCSP]). We related FHx Stroke and FHx MI to subtype of ischemic stroke, age, and the presence of vascular risk factors and performed a systematic review of all studies of FHx Stroke by stroke subtype.

Results— In our population-based studies and in 3 hospital-based studies, FHx Stroke was least frequent in cardioembolic stroke (OR=0.74, 95%CI=0.58 to 0.95, P =0.02) but was equally frequent in the other subtypes. In OXVASC and OCSP, FHx Stroke ( P =0.02), FHx MI ( P =0.04), and FHx of either ( P =0.006) were associated with stroke at a younger age. Only FHx Stroke was associated with previous hypertension (OR=1.59, 95%CI=1.08 to 2.35, P =0.02). FHx MI was more frequent in large-artery stroke (OR=1.63, 95%CI=0.99 to 2.69, P =0.05).

Conclusion— Consistent results in our population-based studies and previous hospital-based studies suggest that inclusion bias is not a major problem for studies of the genetic epidemiology of stroke. Molecular genetic studies might be best targeted at non-cardioembolic stroke and younger patients. However, genetic susceptibility to hypertension may account for a significant proportion of the heritability of ischemic stroke.

Population based study of early risk of stroke after transient ischaemic attack or minor stroke: implications for public education and organisation of services

OBJECTIVE

To estimate the very early stroke risk after a transient ischaemic attack (TIA) or minor stroke and thereby inform the planning of effective stroke prevention services.

DESIGN

Population based prospective cohort study of patients with TIA or stroke.

SETTING

Nine general practices in Oxfordshire, England, from April 2002 to April 2003.

PARTICIPANTS

All patients who had a TIA (n = 87) or minor stroke (n = 87) during the study period and who presented to medical attention.

MAIN OUTCOME MEASURES

Risk of recurrent stroke at seven days, one month, and three months after TIAs and minor strokes.

RESULTS

The estimated risk of recurrent stroke was 8.0% (95% confidence interval 2.3% to 13.7%) at seven days, 11.5% (4.8% to 18.2%) at one month, and 17.3% (9.3% to 25.3%) at three months after a TIA. The risks at these three time periods after a minor stroke were 11.5% (4.8% to 11.2%), 15.0% (7.5% to 22.5%), and 18.5% (10.3% to 26.7%).

CONCLUSIONS

The early risks of stroke after a TIA or minor stroke are much higher than commonly quoted. More research is needed to determine whether these risks can be reduced by more rapid instigation of preventive treatment.