Is family history an independent risk factor for stroke?

Tobacco Use: A Major Risk Factor of Intracerebral Hemorrhage

Spontaneous intracerebral hemorrhage (sICH) is one of the deadliest subtypes of stroke, and no treatment is currently available. One of the major risk factors is tobacco use. In this article, we review literature on how tobacco use affects the risk of sICH and also summarize the known effects of tobacco use on outcomes following sICH. Several studies demonstrate that the risk of sICH is higher in current cigarette smokers compared to non-smokers. The literature also establishes that cigarette smoking not only increases the risk of sICH but also increases hematoma growth, results in worse outcomes, and increases the risk of death from sICH. This review also discusses potential mechanisms activated by tobacco use which result in an increase in risk and severity of sICH. Exploring the underlying mechanisms may help alleviate the risk of sICH in tobacco users as well as may help better manage tobacco user sICH patients.

Evaluation of stroke related risk factors in wake up and non-wake up stroke patients

Wake-Up Stroke (WUS) is defined as a stroke with the unclear onset of symptoms and subsequent neurological deficits which perceived upon awakening. WUS patients are often excluded from acute fibrinolytic and reperfusion therapy due to the unknown exact time of symptoms onset. This study aimed to evaluate patients with and without WUS characteristics and associated risk factors at two tertiary hospitals. First, we prospectively evaluated consecutive patients with stroke symptoms and determined stroke sub groups by using Computed Tomography (CT) scan. Next, demographic and clinical characteristics including past medical and drug consumption history as well as cardiac function index (ejection fraction), LDL (mg/dl) level and hematologic parameters: hemoglobin (Hb); hematocrit (Hct); platelet (Plt) were assessed. Results: 510 patients (56.1% men and 43.9% women) with averaged age of 70 and 72 years were studied, respectively. Of 510 patients, 405 (79.4%) had non-WUS stroke (known-onset stroke) and 105 (20.6%) had WUS strokes (unknown-onset stroke). The WUS occurrence most likely was observed in ischemic stroke compared to hemorrhagic one. No significant differences were found between patients from both groups regarding stroke risk factors. However, hypertension and family history were more common in patients with WUS (p>0.05). Moreover, individuals with a previous cerebrovascular accident in WUS group were almost similar to non-WUS counterparts. No differences also detected in case of hematologic characteristics, heart function index and LDL levels between study groups (p>0.05). Together, wake-up stroke occurs in approximately 20% of stroke subjects. In this study, patients with WUS had more hypertension and family history.

Association of Family History With Cardiovascular Disease in Hypertensive Individuals in a Multiethnic Population

BACKGROUND

Hypertension alone is a poor predictor of the individual risk of cardiovascular disease. Hereditary factors of which hypertension is merely a marker may explain why some hypertensive individuals appear more susceptible to cardiovascular disease, and why some ethnicities have more often seemingly hypertension-related cardiovascular disease than others. We hypothesize that, in hypertensive individuals, a positive family history of cardiovascular disease identifies a high-risk subpopulation.

METHODS AND RESULTS

Healthy Life in Urban Settings (HELIUS) is a cohort study among participants of Dutch, South-Asian Surinamese, African Surinamese, Ghanaian, Turkish, and Moroccan origin aged 70 years and younger. In participants with hypertension (n=6467), we used logistic regression to assess the association of family history of cardiovascular disease with prevalent stroke and nonstroke cardiovascular disease, adjusting for sex, age, education, and smoking. To detect ethnic differences, we tested for interaction between family history and ethnicity and stratified the analysis by ethnicity. A positive family history was associated with a higher prevalence of nonstroke cardiovascular disease (odds ratio [OR], 2.05; 95% CI, 1.65-2.54) and stroke (OR, 1.62; 95% CI, 1.19-2.20). The strongest association of family history with nonstroke cardiovascular disease was found among the Dutch (OR, 2.47; 95% CI, 1.37-4.44) and with stroke among the African Surinamese (OR, 2.17; 95% CI, 1.32-3.57). The interaction between family history and African Surinamese origin for stroke was statistically significant.

CONCLUSIONS

In multiethnic populations of hypertensive patients, a positive family history of cardiovascular disease may be used clinically to identify individuals at high risk for nonstroke cardiovascular disease regardless of ethnic origin and African Surinamese individuals at high risk for stroke.

Association between diabetes mellitus and the occurrence and outcome of intracerebral hemorrhage

OBJECTIVE

Whether diabetes mellitus (DM) is a risk factor for spontaneous intracerebral hemorrhage (ICH) and influences outcome after ICH remains unclear.

METHODS

One reviewer searched Ovid MEDLINE and Embase 1980-2014 inclusive for studies investigating the associations between DM and ICH occurrence or DM and ICH case fatality. Two reviewers independently confirmed each study's eligibility, assessed risk of bias, and extracted data. One reviewer combined studies using random effects meta-analysis.

RESULTS

Nineteen case-control studies involving 3,397 people with ICH and 5,747 people without ICH found an association between DM and ICH occurrence (unadjusted odds ratio [OR] 1.23, 95% confidence interval [CI] 1.04-1.45; I(2) = 22%), which did not differ between 17 hospital-based and 2 population-based studies (pdiff = 0.70), and was similar in the 16 studies that controlled for age and sex (unadjusted OR 1.15, 95% CI 0.95-1.40; I(2) = 14%). This association was not identified in 3 population-based cohort studies in which ICH occurred in 38 (0.66%) of 5,724 people with DM and 448 (0.57%) of 78,702 people without DM (unadjusted risk ratio [RR] 1.27, 95% CI 0.68-2.36; I(2) = 69%). DM was associated with a higher case fatality by 30 days or hospital discharge in 18 cohort studies involving 813 people with DM and 3,714 people without DM (unadjusted RR 1.52, 95% CI 1.28-1.81; I(2) = 49%).

CONCLUSIONS

The findings suggest that there may be modest associations between DM and ICH occurrence and outcome, but further information from large, population-based studies that account for confounding is required before the association can be confirmed.

Lifestyle factors and risk of stroke in Seoul, south Korea

BACKGROUND AND PURPOSE

The importance of stroke risk factors, especially lifestyle associated ones, may differ among different ethnic groups. The purpose of the present study is to elucidate the risk factors for stroke in Seoul, Korea.

SUBJECTS AND METHODS

Three-hundred four stroke patients and 249 age-matched controls were studied. Patients were divided into those with cerebral infarction (CI) and intracerebral hemorrhage (ICH). Using a structured interview, we assessed risk factors for stroke including lifestyle-associated factors: hypertension (HT); diabetes mellitus (DM); cigarette smoking; alcohol drinking; sodium intake; salt taste preference; physical activity and exercise; consumption of vegetables, fat, fish and fruits; body mass index; total body fat; and skinfold thickness of triceps, subscapular, and abdomen. The results were compared between patients and controls, and between CI and ICH.

RESULTS

There were 232 CI and 72 ICH. Multivariate logistic regression analyses revealed the following independent risk factors; for CI in men, HT, DM, high sodium intake, low intake of vegetables, and excessive abdominal skinfold thickness; for ICH in men, HT, heavy alcohol drinking, high sodium intake, excessive abdominal skinfold thickness, and low fat consumption; for CI in women, excessive abdominal skinfold thickness, and low fat consumption; for CI in women, HT, high sodium intake, excessive abdominal skinfold thickness, decreased triceps skinfold thickness, and lack of recent physical exercise. On subgroup comparison, DM was found to be a discriminant risk factor favoring CI (v ICH) in women.

CONCLUSION

Our results showed that in Seoul, Korea, HT is the strongest risk factor for CI and ICH, and high sodium intake, lack of exercise, and central body fat deposition are relatively important factors related to stroke, whereas factors such as cigarette smoking, hypercholesterolemia, and body mass index are not. Low consumption of fat and heavy alcohol drinking appear to be related to the occurrence of ICH. Risk factors for stroke may differ among different ethnic groups and guidelines for stroke prevention should be based on a correct understanding of them.

The insulin-like growth factor-1 gene is associated with cerebral infarction in Japanese subjects

Atherosclerosis leads to cerebral infarction (CI) and the insulin/insulin-like growth factor-1 (IGF1) signaling pathway plays an important role in this process during adult life. The purpose of this study was to investigate the relationship between the human IGF1 gene and CI in the Japanese population via a case-control study that also included a separate analysis of the two gender groups. A total of 155 CI patients and 316 controls were genotyped for six single nucleotide polymorphisms (SNPs) of the human IGF1 gene (rs2162679, rs7956547, rs2288378, rs2072592, rs978458 and rs6218). All data were analyzed for three separate groups: the total subjects, men and women. The logistic regression analysis revealed that the GG + AG variant of rs2162679 (P = 0.047), the AA + GA variant of rs2072592 (P = 0.005) and the CC + TC variant of rs6218 (P = 0.015) exhibited a protective effect for CI in the total subject group. For the women and the total subjects groups, the overall distribution of the haplotype established by rs7956547-rs978458 was significantly different between the CI patients and the non-CI subjects. For the total subjects, the frequency of the T-G haplotype (rs7956547-rs978458) was also significantly higher (P = 0.034), whereas the frequency of the T-A haplotype (rs7956547-rs978458) was significantly lower (P = 0.008) in the CI patients versus the non-CI subjects. For women, the frequency of the T-A haplotype (rs7956547-rs978458) was significantly lower (P = 0.021) in the CI patients as compared with the non-CI subjects. The specific SNPs and haplotypes can be utilized as genetic markers for CI resistance or CI risk.

Parental occurrence of stroke and risk of stroke in their children: the Framingham study

BACKGROUND

Data relating parental history of stroke to stroke risk in offspring remain surprisingly inconsistent, largely because of heterogeneity of study design and the absence of verified, as opposed to historical, data on parental stroke status.

METHODS AND RESULTS

We determined whether prospectively verified parental occurrence of stroke increased incident stroke risk among offspring in a community-based sample by studying 3443 stroke-free Framingham offspring (53% female; mean age, 48+/-14 years) with verified parental stroke status (by 65 years of age) who attended the first, third, fifth, and/or seventh offspring examinations and were followed up for up to 8 years after each baseline examination. Over up to 11,029 such person-observation periods (77,534 person-years), we documented 106 parental strokes by 65 years of age and 128 offspring strokes (74 parental and 106 offspring strokes were ischemic). Using multivariable Cox models adjusted for age, sex, sibship, and baseline stroke risk factors, we observed that parental stroke, both all stroke generally and ischemic stroke specifically, was associated with an increased risk of incident stroke of the same type in the offspring (hazard ratio, 2.79; 95% confidence interval, 1.68 to 4.66; P<0.001 for all stroke; and hazard ratio, 3.15; 95% confidence interval, 1.69 to 5.88; P<0.001 for ischemic stroke). This was true for both maternal and paternal stroke.

CONCLUSIONS

Documented parental stroke by 65 years of age was associated with a 3-fold increase in risk of offspring stroke. This increased risk persisted after adjustment for conventional stroke risk factors. Thus, verified parental stroke may serve as a clinically useful risk marker of an individual's propensity to stroke.

Young strokes in Sri Lanka: an unsolved problem

Stroke in young adults is more common in India and Sri Lanka and the reasons for this are not well understood. The current study was conducted to elucidate the risk factors and radiologic features in young people (age < 45 years) with ischemic stroke. Sociodemographic data, stroke risk factor information, and laboratory investigations were recorded in 41 cases with first-ever ischemic stroke. Most common risk factors for stroke in the 15- to 45-year-old age group were: hypertension, 8 (21%); family history of stroke, 7 (18%); transient ischemic attack, 6 (16%); hyperlipidemia, 3 (8.0%); and diabetes, two (5%). Age group younger than 15 years included 3 girls and one had a mass attached to the posterior mitral valve leaflet. Our observations underscore the importance of the presence of hypertension, family history of stroke, and transient ischemic attack in young adults and thus to adopt preventative strategies.

Risk factors for primary intracerebral hemorrhage in patients in Izumo City, Japan

The annual incidence rate of primary intracerebral hemorrhage (ICH) in Izumo City, Japan, appears to be the highest rate among those reported. Despite improvement of management and surgical therapy, the overall morbidity and mortality after ICH are still high. The author investigated the risk factors for ICH in patients in Izumo. A case-control study of 242 patients (137 men and 105 women with ages ranging from 34 to 97 years) with primary ICH was conducted in Izumo between 1991 and 1998. Hypertension, diabetes mellitus, heart disease, liver disease, alcohol consumption, cigarette smoking, and serum levels of total cholesterol, aspartate aminotransferase, and alanine aminotransferase were assessed as possible risk factors for ICH by using conditional logistic regression. The prevalence of hypertension among ICH patients was 77% and the odds ratio (OR) for hypertension was 17.07 (95% CI: 8.30-35.09), which are much higher than figures reported from Western countries. The OR for hypertension was higher in individuals < or = 69 years of age than in those > or = 70 years of age and lower for lobar hemorrhage than for hemorrhages at other sites. High serum total cholesterol (> or = 220 mg/dl) was the second most important risk factor for ICH (OR: 2.52; 95% CI: 1.23-5.14), and low total cholesterol (< 160 mg/dl) decreased the risk of ICH (OR: 0.47; 95% CI: 0.27-0.82). In contrast, heart disease decreased the risk of ICH, and there was no observed association between alcohol consumption, cigarette smoking, or diabetes mellitus and ICH. This study conducted in Izumo suggests that hypertension is the most important risk factor for ICH and contrary to most previous studies indicates that serum total cholesterol concentration is also positively associated with the risk of ICH. In contrast, heart disease may decrease the risk of ICH.

Case-control studies in the genomic era: a clinician's guide

The goal of case-control association studies is to find genetic variants in the human genome that influence common traits. The Human Genome and HapMap projects have added fresh impetus to this goal by cataloguing the raw genetic data behind human DNA variation. Studies that associate these genetic variants with phenotype improve both molecular diagnostics and drug discovery and offer clinicians important opportunities to improve care of patients. In this review I focus on case-control studies, which are the most widely used design and expected to be the most powerful. I also address the problem of case-control non-replication, which is widespread despite enormous effort and use of resources. Important causes of non-replication include inadequate statistical power to detect small and moderate effects, phenotype heterogeneity, population stratification, publication bias, and multiple comparison testing.

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.

Family history as a risk factor for stroke in young women

BACKGROUND

Family history of stroke (FHS) is associated with risk of stroke in middle-aged to elderly populations. However, few studies have examined this association in younger women or by stroke type. A population-based, case-control study was conducted to examine the association of FHS and risk of stroke in young women, and to determine whether the association is independent of other stroke risk factors.

METHODS

Cases were women aged 18 to 44 years, with first, nonfatal ischemic (n =49) and hemorrhagic (n = 63) strokes in western Washington State in 1991 to 1995. Demographically similar community controls (n = 446) were identified through random-digit telephone dialing. Information on FHS in first-degree relatives (parents and siblings) and other risk factors was obtained through an interview. Person-years (P-Y) at risk of stroke for relatives of each subject were included in polytomous logistic regression models to adjust for family size. The analysis was conducted between 1999 and 2000.

RESULTS

After adjustment for age and P-Y, FHS in first-degree relatives was significantly associated with an increased risk of hemorrhagic (odds ratio [OR]=2.6, 95% confidence interval [CI]=1.5-4.3) and ischemic stroke (OR=2.1, 95% CI=1.2-3.9). FHS remained associated with risk of hemorrhagic stroke (OR=2.4, 95% CI=1.4-4.1) and ischemic stroke (OR=1.8, 95%CI=0.9-3.5) after further adjustment for diabetes, hypertension, hypercholesterolemia, body mass index, physical activity, smoking, alcohol, and family history of myocardial infarction. Findings were similar when associations with parental and sibling FHS were examined separately.

CONCLUSIONS

Family history of stroke is a risk factor for both hemorrhagic and ischemic strokes among young women.

Physiologic monitoring and anesthesia considerations in acute ischemic stroke

Acute ischemic stroke is considered a neurologic emergency. The perioperative anesthesia management of acute ischemic stroke is challenging owing to the dynamic pathophysiology of the disease itself and the patients' comorbid factors and conditions. Herein, the authors review preoperative assessment, intraoperative and postoperative physiologic monitoring, and anesthesia management, with a focus on the control of the cerebrovascular and cardiovascular circulations. Issues specific to anesthesia monitoring and management in the radiology suite are emphasized.

Systematic Review of Methods and Results of Studies of the Genetic Epidemiology of Ischemic Stroke

BACKGROUND AND PURPOSE

To design appropriate molecular genetic studies, we first need to understand the genetic epidemiology of stroke. We therefore performed a systematic review of the literature to assess the heritability of stroke according to methodological quality of studies and to determine any heterogeneity in findings between studies and possible publication bias.

METHODS

We searched for twin studies and studies of family history of stroke using bibliographic databases and by hand-searching reference lists and journals. Odds ratios (ORs) for family history as a risk factor for stroke were calculated within studies and combined by meta-analysis. Heterogeneity between studies, methodological quality of studies, and the influence of the age at which stroke occurred in both probands and relatives were assessed.

RESULTS

We identified 53 independent studies (3 twin, 33 case-control, and 17 cohort). Monozygotic twins were more likely to be concordant than dizygotic twins (OR, 1.65; 95% CI, 1.2 to 2.3; P=0.003). A positive family history was a risk factor for stroke in both case-control (OR, 1.76; 95% CI, 1.7 to 1.9; P<0.00001) and cohort (OR, 1.30; 95% CI, 1.2 to 1.5; P<0.00001) studies. However, there was major heterogeneity between studies (cohort P=0.0001; case-control P<0.00001), with much stronger associations in small studies and methodologically less rigorous studies. Moreover, studies that reported insufficient data to allow meta-analysis tended to have found weaker associations. Family history of stroke was more frequent in studies that were confined to probands or relatives aged <70 years. However, few studies considered the number of affected and unaffected relatives, only 2 studies considered stroke phenotypes in detail, and only 19 studies (38%) adjusted associations for intermediate phenotypes. No twin study, only 5 cohort studies (26%), and 20 case-control studies (61%) differentiated between ischemic and hemorrhagic stroke in the proband. Family history of stroke was more frequent in large- and small-vessel stroke than in cardioembolic stroke. There were very few data on the influence of family history on stroke severity and no data on stroke recovery.

CONCLUSIONS

Twin studies suggest a small genetic contribution to stroke, but reliable interpretation of published family history studies is undermined by major heterogeneity, insufficient detail, and potential publication and reporting bias. More detailed large-scale genetic epidemiology is required.

Risk factors for intracerebral hemorrhage in the general population: a systematic review

BACKGROUND AND PURPOSE

Although data on some risk factors for intracerebral hemorrhage (ICH) already are beyond doubt, for other factors, the evidence is less clear. We performed a systematic overview of case-control and cohort studies on risk factors for ICH.

METHODS

We searched MEDLINE, LILACS, EXTRAMED, and Pascal from 1966 to 2001 to identify studies. Studies were included if they met predefined methodological criteria. When possible, 2x2 tables were extracted and combined with the Mantel-Haenszel method. Summary odds ratios (ORs) were calculated for case-control studies, and summary relative risks (RRs) were found for cohort studies and for case-control and cohort studies combined.

RESULTS

Fourteen case-control and 11 cohort studies were identified. We could not always combine the results of case-control and cohort studies. In cohort studies, the crude RR for age (every 10-year increase) was 1.97 (95% confidence interval [CI], 1.79 to 2.16). In case-control studies, the crude OR for high alcohol intake was 3.36 (95% CI, 2.21 to 5.12) and for hypertension was 3.68 (95% CI, 2.52 to 5.38). Two cohort studies showed an increasing risk of ICH with increasing degree of hypertension. In cohort and case-control studies combined, the crude RR for sex (male versus female) was 3.73 (95% CI, 3.28 to 4.25); for current smoking, 1.31 (95% CI, 1.09 to 1.58); and for diabetes, 1.30 (95% CI, 1.02 to 1.67).

CONCLUSIONS

Risk factors for ICH appeared to be age, male sex, hypertension, and high alcohol intake. High cholesterol tends to be associated with a lower risk of ICH. We could not assess whether these risk factors are independent.

Evaluating the genetic component of ischemic stroke subtypes: a family history study

BACKGROUND AND PURPOSE

Twin and family history studies support a role for genetic factors in stroke risk. Because the etiology of ischemic stroke is heterogeneous, genetic factors may vary by etiologic subtype. We determined the familial aggregation of stroke risk in different stroke phenotypes and used the results to model estimated sample size requirements for case-control studies.

METHODS

One thousand consecutive white subjects with ischemic stroke and 800 white controls matched for age and sex were recruited. A first-degree family history of stroke and myocardial infarction was obtained by structured interview. Stroke subtype was determined with the use of modified Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria.

RESULTS

A family history of stroke at < or =65 years was a significant risk factor for large-vessel disease (odds ratio [OR], 2.24; 95% CI, 1.49 to 3.36; P<0.001) and for small-vessel disease (OR, 1.93; 95% CI, 1.25 to 2.97; P=0.003). When only cases aged <or =65 years were considered, these ORs increased to 2.93 (95% CI, 1.68 to 5.13) (P<0.001) and 3.15 (95% CI, 1.81 to 5.50) (P<0.001), respectively. No significant associations were seen for cardioembolic stroke or stroke of undetermined etiology.

CONCLUSIONS

A family history of vascular disease is an independent risk factor for both large-vessel atherosclerosis and small-vessel disease, especially in cases presenting before age 65 years. The estimated sample sizes for case-control studies illustrate how candidate gene studies for ischemic stroke might be made more effective by focusing on these specific phenotypes, in which the genetic component of the disease appears to be strongest.

Family history of stroke in stroke types and subtypes

Many studies have provided data showing that family history of stroke (FHS) is associated with an increased risk of stroke. The association of the FHS with the various stroke subtypes has not been adequately studied. The purpose of this study was to assess the association of the FHS with the two major stroke types (cerebral haematomas and ischaemic strokes) and the four stroke subtypes (cardioembolic, large artery disease, small artery disease, and undetermined) in a Greek population. The FHS was obtained from 421 consecutive acute stroke patients and from 239 matched control subjects. Positive FHS was observed in 49% of all stroke patients compared with 28% of the control subjects [adjusted OR=2.06 (95% confidence intervals (CI) 1.42-3.00)]. Haematomas, ischaemic strokes, and from the ischaemic strokes, both large and small artery disease strokes were strongly associated with positive FHS compared with the control subjects [adjusted OR=2.06 (95% CI 9-3.04), 2.07 (95% CI 1.09-3.91), 2.05 (95% CI 1.24-3.38), and 2.76 (95% CI 1.55-4.91), respectively]. There was no difference between maternal and paternal heritable contribution.In conclusion, FHS was found in this study to be an independent risk factor for all strokes combined, for each stroke type, and for the large and small-artery disease stroke subtypes, but not for the cardioembolic and undetermined stroke subtypes.

Genetic liability in stroke: a long-term follow-up study of Danish twins

BACKGROUND AND PURPOSE

Few studies have assessed the overall importance of genetic factors on stroke risk, and the results have been contradictory. We used a large, population-based twin register and nationwide registries of death and hospitalization with long-term follow-up to estimate the effect of genetic factors on the risk of stroke.

METHODS

Through the population-based Danish Twin Register, we identified same-sex twin pairs born in 1870 through 1952 for whom at least 1 twin was recorded under a stroke diagnosis in the Register of Causes of Death or the Danish National Discharge Register. From the day of the first stroke event in each twin pair, the live co-twins were followed up for stroke. In survival analyses, we estimated the age- and sex-adjusted effect of zygosity on the risk of stroke death or hospitalization for stroke. Concordance rates, tetrachoric correlations, and heritability were also assessed.

RESULTS

Thirty-five of 351 monozygotic pairs (10%) and 34 of 639 dizygotic pairs (5%) were concordant for stroke death. The age- and sex-adjusted relative risk of stroke death in monozygotic compared with dizygotic co-twins was 2.1 (95% CI, 1.3 to 3.3). The probandwise concordance rates were 0.18 (95% CI, 0.14 to 0.22) for monozygotic and 0.10 (95% CI, 0.08 to 0.13) for dizygotic pairs. Thirty-three of 309 monozygotic pairs (11%) and 39 of 560 dizygotic pairs (7%) were concordant for stroke hospitalization or stroke death. The age- and sex-adjusted relative risk of stroke hospitalization or stroke death in monozygotic compared with dizygotic co-twins was 1.5 (95% CI, 0.9 to 2.4). The probandwise concordance rates were 0.19 (95% CI, 0.15 to 0.24) for monozygotic and 0.13 (95% CI, 0.10 to 0.16) for dizygotic pairs. The heritability estimates were 0.32 for the liability to stroke death and 0.17 for the liability to stroke hospitalization or stroke death.

CONCLUSIONS

The observed increased risk of stroke death and stroke hospitalization in monozygotic compared with dizygotic co-twins suggests that genetic factors increase the risk of stroke and that the size of this effect is moderate.

Parental history of stroke predicts subclinical but not clinical stroke: the Atherosclerosis Risk in Communities Study

BACKGROUND AND PURPOSE

An individual with a positive family history of a disease may be at increased risk for the disease. We sought to examine whether parental history of stroke is associated with subclinical or clinical stroke in the Atherosclerosis Risk in Communities (ARIC) Study, and whether any observed association is independent of established stroke risk factors.

METHODS

Parental history of stroke was determined by home interview at the baseline examination. Cerebral MRI was performed on individuals from 2 ARIC field centers. Subclinical cerebral infarct cases (n=202) were defined by the presence of cerebral infarcts >3 mm. The comparison group for the subclinical cases included all individuals participating in the MRI examination who were not identified as a subclinical case (n=1533). Incidence of clinical ischemic stroke was determined by following the ARIC cohort for potential cerebrovascular events. Two hundred sixty-one validated ischemic strokes were identified; 13 775 individuals from the ARIC cohort did not experience an ischemic event.

RESULTS

Parental history of stroke was significantly associated with subclinical stroke after adjusting for age, gender, and race (OR 1.67, 95% CI1.23 to 2.26) and after further adjustment for multiple stroke risk factors (OR1. 64, 95% CI1.20 to 2.24). Parental history of stroke was not a significant predictor of clinical stroke in either adjustment model.

CONCLUSIONS

The observed increased risk of subclinical stroke among individuals with a parental history of stroke is consistent with the expression of genetic susceptibility, a shared environment, or both in the etiology of stroke. This effect did not appear to be mediated by established stroke risk factors. Parental history of stroke does not confer an increased risk of clinical stroke in this sample of middle-aged Americans.

Genetic predisposition to stroke in relatives of hypertensives

BACKGROUND AND PURPOSE

The genetic basis of stroke is poorly understood. We evaluated patterns of familial aggregation of hypertension and stroke to test the hypothesis that inherited susceptibility to these disorders may be determined by a common set of factors.

METHODS

Genealogical and medical history information was obtained for a cohort of 354 hypertensive probands ascertained in a clinic-based setting, their 1427 first-degree relatives, and 239 of their spouses. Risks of stroke and hypertension in biological and nonbiological relatives were compared with the logistic model of the generalized estimating equations adjusted for age and sex.

RESULTS

The risk of hypertension was higher for the parents and siblings of the probands than for spouses (odds ratio [OR]=2.4; 95% CI, 1.8 to 3.4; OR=2.2; 95% CI, 1.6 to 3.0, respectively). When the spouses were used as a reference group, the risk of stroke for parents of the hypertensive probands was 7.3 times higher (OR=7.3; 95% CI, 3.6 to 14.8), while a nonsignificant but slightly increased risk for siblings (OR=1.6; 95% CI, 0.8 to 3.3) was observed. Controlling for hypertension, obesity, smoking, coronary heart disease, diabetes, and cholesterol resulted in decreased estimates of the risk of stroke for parents and siblings (OR(parents)=5.4; 95% CI, 2.6 to 11.2; OR(siblings)=1.2; 95% CI, 0.6 to 2.5). The risk of stroke was significantly higher for hypertensive parents and siblings than for nonhypertensive parents (OR=5.2; 95% CI, 2.8 to 9. 7) and siblings (OR=5.8; 95% CI, 2.1 to 15.9). A history of hypertension was not associated with an increased risk for stroke in spouses (OR=0.7; 95% CI, 0.2 to 3.1). The risk of stroke in hypertensive relatives of probands with stroke was higher than that of the normotensive relatives (OR=13.4). A less elevated risk ratio was observed in the relatives of probands who did not have a stroke (OR=4.0).

CONCLUSIONS

Our data showing a higher occurrence of hypertension and stroke in parents of hypertensive probands compared with spouses suggest that some of the genetic factors predisposing to these conditions may be the same. The slightly increased risk to siblings compared with spouses was not significant, suggesting that elucidation of these factors through family studies of stroke may be difficult because of secular trends toward improved treatment for hypertension. Although a history of hypertension increases the risk of stroke among parents and siblings, multivariate analyses revealed a familial component to stroke independent of hypertension.