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Objective Observational studies point to an inverse correlation between low‐density lipoprotein (LDL) cholesterol levels and risk of intracerebral hemorrhage (ICH), but it remains unclear whether this association is causal. We tested the hypothesis that genetically elevated LDL is associated with reduced risk of ICH. Methods We constructed one polygenic risk score (PRS) per lipid trait (total cholesterol, LDL, high‐density lipoprotein [HDL], and triglycerides) using independent genomewide significant single nucleotide polymorphisms (SNPs) for each trait. We used data from 316,428 individuals enrolled in the UK Biobank to estimate the effect of each PRS on its corresponding trait, and data from 1,286 ICH cases and 1,261 matched controls to estimate the effect of each PRS on ICH risk. We used these estimates to conduct Mendelian Randomization (MR) analyses. Results We identified 410, 339, 393, and 317 lipid‐related SNPs for total cholesterol, LDL, HDL, and triglycerides, respectively. All four PRSs were strongly associated with their corresponding trait (all p 0.05). MR analyses indicated that 1mmol/L (38.67mg/dL) increase of genetically instrumented total and LDL cholesterol were associated with 23% (OR = 0.77; 95% CI = 0.65–0.98; p = 0.03) and 41% lower risks of ICH (OR = 0.59; 95% CI = 0.42–0.82; p = 0.002), respectively. Interpretation Genetically elevated LDL levels were associated with lower risk of ICH, providing support for a potential causal role of LDL cholesterol in ICH.

Objective: Prior studies investigating the association between APOE alleles epsilon 2/epsilon 4 and risk of intracerebral hemorrhage (ICH) have been inconsistent and limited to small sample sizes, and did not account for confounding by population stratification or determine which genetic risk model was best applied. Methods: We performed a large-scale genetic association study of 2189 ICH cases and 4041 controls from 7 cohorts, which were analyzed using additive models for epsilon 2 and epsilon 4. Results were subsequently meta-analyzed using a random effects model. A proportion of the individuals (322 cases, 357 controls) had available genome-wide data to adjust for population stratification. Results: Alleles epsilon 2 and epsilon 4 were associated with lobar ICH at genome-wide significance levels (odds ratio [OR] = 1.82, 95% confidence interval [CI] = 1.50-2.23, p = 6.6 x 10(-10); and OR = 2.20, 95%CI = 1.85-2.63, p = 2.4 x 10(-11), respectively). Restriction of analysis to definite/probable cerebral amyloid angiopathy ICH uncovered a stronger effect. Allele epsilon 4 was also associated with increased risk for deep ICH (OR = 1.21, 95% CI = 1.08-1.36, p = 2.6 x 10(-4)). Risk prediction evaluation identified the additive model as best for describing the effect of APOE genotypes. Interpretation: APOE epsilon 2 and epsilon 4 are independent risk factors for lobar ICH, consistent with their known associations with amyloid biology. In addition, we present preliminary findings on a novel association between APOE epsilon 4 and deep ICH. Finally, we demonstrate that an additive model for these APOE variants is superior to other forms of genetic risk modeling previously applied. ANN NEUROL 2010;68:934-943

Risk for ischemic stroke is mediated by both environmental and genetic factors. Although several environmental exposures have been implicated, relatively little is known about the genetic basis of predisposition to this disease. Recent studies in Iceland identified risk polymorphisms in two putative candidate genes for ischemic stroke: phosphodiesterase 4D (PDE4D) and 5-lipoxygenase activating protein (ALOX5AP). A collection of North American sibling pairs concordant for ischemic stroke and two cohorts of prospectively ascertained North American ischemic stroke cases and control subjects were used for evaluation of PDE4D and ALOX5AP. Although no evidence supported linkage of ischemic stroke with either of the two candidate genes, single-nucleotide polymorphisms and haplotypic associations were observed between PDE4D and ischemic stroke. There was no evidence of association between variants of ALOX5AP and ischemic stroke. These data suggest that common variants in PDE4D may contribute to the genetic risk for ischemic stroke in multiple populations.