Background Smoking and hypertension increase the risk of aneurismal subarachnoid haemorrhage (SAH) two to threefold whereas a familial predisposition increases the risk sixfold. We assessed the additional risk of smoking and hypertension for the presence of an intracranial aneurysm (IA) in first-degree relatives of patients with familial SAH.

Methods We studied first-degree relatives of patients with familial SAH who were screened for the presence of aneurysms. RRs with corresponding 95% CIs for the risk of IA were calculated for smoking and hypertension.

Results The RRs were 1.5 (95% CI 0.7 to 3.2) for smoking, 1.9 (95% CI 1.0 to 3.7) for hypertension and 2.7 (95% CI 1.4 to 5.3) for smoking plus hypertension. The increased RR for hypertension was found in both women and men, but the increased RR for smoking was found in women only.

Conclusion The extent of the increased risk of smoking and hypertension for the presence of IA in first-degree relatives of patients with familial SAH is similar to that in patients without familial predisposition. Risk factor profiles should be included in future genetic studies.