Background and aim Genetic factors play a role in susceptibility to subarachnoid haemorrhage, but little is known about which genes are involved. Recently, genome wide association studies have identified the 9p21 region as a risk locus for intracranial aneurysms (IA). The aim of the present study was to examine the possible association between 9p21 and ruptured IA—that is, aneurysmal subarachnoid haemorrhage (aSAH)—in a Swedish population. There is one study showing an association between 9p21 and arterial stiffness, and arterial stiffness plays a role in the development of hypertension. Therefore, a second aim was to investigate whether a putative association is independent of hypertension.
Methods The study comprised 183 patients presenting with aSAH to the Neurointensive Care Unit at Sahlgrenska University Hospital and 366 healthy, age and sex matched population based controls. As the causative functional variant in the region has not yet been identified, a 44 kbp region on 9p21 was tagged using HapMap. Six single nucleotide polymorphism (SNPs) were genotyped.
Results Two SNPs, rs10757278 and rs1333045, showed significant associations with aSAH in univariate analyses. After adjustment for hypertension as well as for smoking, the association between aSAH and rs10757278 remained significant with an OR for aSAH of 1.42 (95% CI 1.08 to 1.87; p=0.01) for the uncommon G allele.
Conclusions These data confirm earlier results showing that 9p21 is a susceptibility locus for IA, and that this association is present in a Swedish sample restricted to ruptured IA. For the first time, it has been demonstrated that this association is independent of hypertension.
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Funding This study was supported by the Swedish Research Council (K2008 65X-14605-06-3), grants from the Swedish state under the ALF agreement (ALFGBG-11206), the Swedish Heart Lung Foundation (20070404), the Swedish Stroke Association, the Rune and Ulla Amlövs Foundation for Neurological Research, the John and Brit Wennerström Foundation for Neurological Research and the Yngve Land Foundation for Neurological Research. The funding sources did not influence study design, collection, analysis or interpretation of the data, or drafting or writing of the manuscript.
Competing interests None.
Ethics approval This study was conducted with the approval of the the medical ethics committee at the University of Gothenburg.
Provenance and peer review Not commissioned; externally peer reviewed.