Håkan Lövkvist

Common Genetic Variants on Chromosome 9p21 Confers Risk of Ischemic Stroke: A Large-Scale Genetic Association Study

Background—Epidemiological studies indicate a genetic contribution to ischemic stroke risk, but specific genetic variants remain unknown, with the exception of a few rare variants. Recent genome-wide association studies identified and replicated common genetic variants on chromosome 9p21 to confer risk of coronary heart disease. We examined whether these variants are associated with ischemic stroke. Methods and Results—We genotyped 6 common genetic variants on chromosome 9p21, previously associated with coronary artery disease in genome-wide association studies, in 2 population-based studies in southern Sweden, the Lund Stroke Register (n=1837 cases, 947 controls) and the Malmö Diet and Cancer study (MDC; n=888 cases, 893 controls). We examined association in each study and in the pooled dataset. Adjustments were made for cardiovascular risk factors and further for previous myocardial infarction in MDC. We found a modest increase in ischemic stroke risk for 2 common (minor allele frequencies 0.46 to 0.49) variants, rs2383207 (P=0.04 in Lund Stroke Register, P=0.01 in MDC) and rs10757274 (P=0.03 in Lund Stroke Register, P=0.03 in MDC), in each sample independently. The strength of the association increased when samples were pooled with an odds ratio of 1.15 (95% CI, 1.05 to 1.25; P=0.002) for the strongest variant rs2383207. Results were similar after adjustment for clinical covariates. rs1333049 also showed significant association in MDC, which increased in the pooled sample (P=0.004). Conclusions—In this large sample (n=4565), we detected common genetic determinants for ischemic stroke on chromosome 9p21. Our findings indicate that ischemic stroke shares pathophysiological determinants with coronary heart disease and other arterial diseases and highlight the need for large sample sizes in stroke genetics.

A common missense variant in the ATP receptor P2X7 is associated with reduced risk of cardiovascular events.

Background and Purpose Extracellular adenosine triphosphate (ATP) regulates inflammatory cells by activation of the P2X7 receptor. We hypothesized that polymorphisms in P2RX7 influence the risk of ischemic heart disease (IHD), ischemic stroke (IS) and cardiovascular risk factors and tested this hypothesis using genetic association studies. Methods Two loss-of-function SNPs in P2RX7 were genotyped in 1244 IHD cases and 2488 controls as well as 5969 individuals with cardiovascular risk factors. Eleven SNPs in a 250 kb region on chromosome 12 spanning P2RX7 as well as neighboring genes OASL, P2RX4 and CAMKK2 were genotyped in 4138 individuals with IS and 2528 controls. Association was examined using linear and logistic regression models with an additive genetic model. Results The common loss-of-function variant rs3751143 was significantly associated with a decreased risk of IHD in smokers (P = 0.03) as well as decreased risk of IS (OR 0.89; 95% CI = 0.81–0.97; P = 0.012). In addition, an intronic SNP in CAMKK2, rs2686342, were associated with a decreased risk of IS (OR 0.89; 95% CI = 0.82–0.97; P = 0.011). In subgroup analyses, both SNPs were associated with decreased risk of IS in individuals with hypertension (P = 0.045 and 0.015, respectively). Conclusions A common loss-of-function missense variant in the gene encoding the P2X7 receptor is associated with reduced risk of IS and with IHD in smokers. These findings might implicate a role of purinergic signaling in atherogenesis or atherothrombosis.

Genetic Variation Within the Interleukin-1 Gene Cluster and Ischemic Stroke

Background and Purpose— Evidence is emerging that inflammation plays a key role in the pathophysiology of ischemic stroke (IS). The aim of this study was to investigate whether genetic variation in the interleukin-1&agr;, interleukin-1&bgr;, and interleukin-1 receptor antagonist genes (IL1A, IL1B, and IL1RN) is associated with IS and/or any etiologic subtype of IS. Methods— Twelve tagSNPs were analyzed in the Sahlgrenska Academy Study on Ischemic Stroke (SAHLSIS), which comprises 844 patients with IS and 668 control subjects. IS subtypes were defined according to the Trial of Org 10172 in Acute Stroke Treatment criteria in SAHLSIS. The Lund Stroke Register and the Malmö Diet and Cancer study were used as a replication sample for overall IS (in total 3145 patients and 1793 control subjects). Results— The single nucleotide polymorphism rs380092 in IL1RN showed an association with overall IS in SAHLSIS (OR, 1.21; 95% CI, 1.02–1.43; P=0.03), which was replicated in the Lund Stroke Register and the Malmö Diet and Cancer study sample. An association was also detected in all samples combined (OR, 1.12; 95% CI, 1.04–1.21; P=0.03). Three single nucleotide polymorphisms in IL1RN (including rs380092) were nominally associated with the subtype of cryptogenic stroke in SAHLSIS, but the statistical significance did not remain after correction for multiple testing. Furthermore, increased plasma levels of interleukin-1 receptor antagonist were observed in the subtype of cryptogenic stroke compared with controls. Conclusion— This comprehensive study, based on a tagSNP approach and replication, presents support for the role of IL1RN in overall IS.

Genetic Variant on Chromosome 12p13 Does Not Show Association to Ischemic Stroke in 3 Swedish Case-Control Studies

Background and Purpose— In a genome-wide association study and subsequent case-control studies, the single-nucleotide polymorphism rs12425791 on chromosome 12p13 was reported to be associated with ischemic stroke, but this could not be validated in a recent well-powered study. We therefore investigated whether an association between ischemic stroke and rs12425791 could be detected in 3 different case-control studies from the southwest of Sweden. Methods— We examined 3606 patients with ischemic stroke and 2528 controls from 3 independent case-controls studies. Results— No significant association between ischemic stroke and the single-nucleotide polymorphism rs12425791 was detected in any of the 3 case-control samples or in the samples combined. The odds ratio for ischemic stroke for the minor allele in the combined sample was 1.02 (95% CI, 0.93 to 1.13). Conclusions— The single-nucleotide polymorphism rs12425791 does not confer a substantial risk for ischemic stroke in our population. Our results support a recent large study including other European populations.

Ischaemic stroke in hypertensive patients is associated with variations in the PDE4D genome region

Previous Icelandic studies reported that single nucleotide polymorphisms (SNPs) in the phosphodiesterase 4D (PDE4D) region and the 5-lipoxygenase activating protein ALOX5AP were associated with ischaemic stroke, whereas other studies reported ambiguous findings. We examined 932 ischaemic stroke patients from a Swedish population-based stroke register, and 396 control subjects. We assessed possible associations between ischaemic stroke and nine preselected SNPs in the chromosome regions of the PDE4D gene, including rs12188950 (SNP45) and rs3887175 (SNP39); the ALOX5AP gene, including rs17222814 (SG13S25) and the promoter region of the MHC class II transactivator, MHC2TA. The T allele of SNP45 showed negative association with ischaemic stroke (odds ratio, OR=0.72; 95% confidence interval (CI): 0.58–0.91; P=0.0055). Among hypertensive subjects, this influence of the T allele of SNP45, and the T allele of SNP39, were more pronounced (with OR=0.52; 95% CI: 0.37–0.73; P=0.0001 and OR=0.57; 95% CI: 0.41–0.79; P=0.0007, respectively). These SNPs also interacted with hypertension with a relative excess risk due to interaction of −1.66 (P=0.0002) for SNP45 and −1.65 (P=0.0005) for SNP39. The P-values remained significant after correction for multiple testing. Among nonhypertensives, the A allele of SG13S25 indicated increased stroke risk (OR=1.82; 95% CI: 1.21–2.74; P=0.0039; not significant after Bonferroni correction). SNP45 was associated with ischaemic stroke even when controlling for hypertension, diabetes, heart disease and smoking. Our meta-analysis of 13 studies (including ours) showed no overall influence of SNP45 on ischaemic stroke. However, the 13 studies may differ because of nonrandom causes, as suggested by the heterogeneity test (P=0.042). This might support previously undetected mechanisms causing fluctuating ischaemic stroke risk.

Genetic variants in serum and glucocortocoid regulated kinase 1, a regulator of the epithelial sodium channel, are associated with ischaemic stroke.

Objective Serum and glucocorticoid regulated kinase 1 (SGK1) expression is increased by aldosterone and is a key regulator of the amiloride-sensitive sodium channel (ENaC) in the distal nephron. We have previously shown that two SNPs in SGK1 (rs1057293 and rs1743966) are associated with blood pressure variation and blood pressure progression in the general population. Therefore, we tested the association of these variants with ischaemic stroke. Methods Using logistic regression, we analysed rs1057293 and rs1743966 for association with ischaemic stroke in two independent age-matched and sex-matched case–control groups from the twin cities of Lund (cases n = 1837 and controls n = 947) and Malmö (cases n = 888 and controls n = 893) in the Scania region of southern Sweden. Results In additive models adjusted for hypertension, smoking and diabetes, the major allele (G) of rs1057293 was associated (odds ratio, 95% confidence interval; P value) with ischaemic stroke with similar effect size in both studies; in Lund (1.35, 1.11–1.64; P = 0.002) and Malmö (1.30, 1.03–1.65; P = 0.027). When the two studies were pooled, the overall association was 1.32, 1.14–1.52; P < 0.001. The major allele of rs1743966 (A), which was in linkage disequilibrium with rs1057293, showed a similar trend as rs1057293 G-allele but with slightly weaker effect size and P value. Conclusion In two independent but ethnically similar populations, we observed an association between genetic variants in SGK1 and ischaemic stroke. Interestingly, the association seems to be at least partially independent of blood pressure. This could imply that cerebrovascular ENaC or other SGK1-regulated proteins may be of importance for development of ischaemic stroke.

Prevalence of Stroke and Vascular Risk Factors among First-Degree Relatives of Stroke Patients and Control Subjects

Background: Genetic and environmental factors may be of importance for stroke risk. We assessed the prevalence of stroke and vascular risk factors among first-degree relatives and spouses of stroke patients and control subjects. Methods: As a part of the Lund Stroke Register study, we asked 925 consecutive patients with first-ever stroke and 286 control subjects to complete a questionnaire about all their first-degree relatives and spouses. The questionnaires addressed whether these relatives had been affected by stroke or TIA, hypertension, heart disease, diabetes mellitus, and if they were smokers. Results: A total of 606 patients and 261 control subjects returned the questionnaire, providing information on 4,972 first-degree relatives and 738 spouses. The prevalence of stroke or TIA was 12.3% among first-degree relatives of patients and 7.5% among first-degree relatives of control subjects (OR 1.74, 95% CI 1.36–2.22). Corresponding results for hypertension were 21.0 and 16.7% (OR 1.33, 95% CI 1.10–1.60). The prevalences of heart disease, diabetes mellitus and smoking did not differ significantly between first-degree relatives of patients and control subjects. Spouses of patients and control subjects had similar prevalences of stroke or TIA and vascular risk factors. Conclusions: The prevalences of stroke or TIA and hypertension are higher among first-degree relatives of stroke patients than among first-degree relatives of control subjects. This, and the lack of differences between spouses of patients and control subjects, indicates that an increased risk of stroke may in part be explained by heritability of hypertension.

A large-sample assessment of possible association between ischaemic stroke and rs12188950 in the PDE4D gene

Previous reports have shown ambiguous findings regarding the possible associations between ischaemic stroke (IS) and single nucleotide polymorphisms (SNPs) in the phosphodiesterase 4D (PDE4D) gene region. The SNP rs12188950 (or SNP45) has often been studied in this context. We performed a multi-centre study involving a large sample of 2599 IS patients and 2093 control subjects from the south and west regions of Sweden to replicate previous studies regarding IS risk and rs12188950. Subjects from Lund Stroke Register (LSR), Malmö Diet and Cancer Study (MDC) and Sahlgrenska Academy Study on Ischemic Stroke (SAHLSIS) were enroled. Subgroups of participants with hypertension and participants <55 years of age, as well as the TOAST subgroups large vessel disease, small vessel disease and cardioembolism, were also assessed. Univariate odds ratios (ORs) and ORs controlling for hypertension, diabetes and current smoking were calculated. We additionally performed a meta-analysis including 10 500 patients and 10 102 control subjects from 17 publications (including the present study). When assessing pooled data from LSR, MDC and SAHLSIS we obtained no association between IS and rs12188950 for all participants (OR=0.93; 95% confidence interval (CI): 0.83–1.05). Significant associations were not found for hypertensive participants or participants with age <55, or when separately evaluating patients from the three different TOAST subgroups. The meta-analysis showed no significant overall estimate (OR=0.96; 95% CI: 0.89–1.04) with significant heterogeneity for random effect (P=0.042). No effect from rs12188950 on IS was found from either our pooled multi-centre data or the performed meta-analysis. We did not find any association between the examined subgroups and rs12188950 either.

Cognitive function in stroke survivors: A 10-year follow-up study

Post‐stroke cognitive impairment (PSCI) has considerable impact on patients and society. However, long‐term studies on PSCI are scarce and may be influenced by assessment methods and selection bias. We aimed to (i) assess the prevalence of long‐term PSCI; (ii) compare two common cognitive assessment instruments; and (iii) compare cognitive function of long‐term stroke survivors with non‐stroke persons.

Multiplicity of Risk Factors in Ischemic Stroke Patients: Relations to Age, Sex, and Subtype - A Study of 2,505 Patients from the Lund Stroke Register.

Background: The prevalence of risk factors for ischemic stroke may vary between different groups of stroke patients. We examined the distribution of individual well-established risk factors as well as the multiplicity of risk factors in different age groups and among subtypes. Methods: In the Lund Stroke Register, we consecutively enrolled 2,505 patients with first-ever ischemic stroke from 2001 to 2009 and registered hypertension, diabetes mellitus, heart disease, current smoking, hypercholesterolemia as well as stroke subtype. Results: Among young patients (<55 years), at least 50% had ≥2 risk factors and 20-25% had ≥3 risk factors. In patients aged 55 years or older, the proportion with ≥2 risk factors was 70-80% and with ≥3 risk factors 35-45%. Men and women had a similar burden of risk factors. Approximately 50% of the cases classified as cardioembolism (CE) and large artery atherosclerosis (LAA) had ≥3 risk factors, which was significantly more than the other TOAST (Trial of Org 10172 in Acute Stroke Treatment) subtypes (CE p < 0.001, LAA p = 0.001). Conclusions: The prevalence of well-established risk factors is similar among young and old stroke patients with large proportions (50-80%) having ≥2 risk factors. Even though the prevalence of well-established risk factors differs between pathogenetic subtypes, these risk factors as well as the multiplicity of risk factors seem to be of clinical importance in all major subtypes of ischemic stroke.