Relation between age and number of aneurysms in patients with subarachnoid haemorrhage

BACKGROUND: Because age and the presence of atherosclerosis are risk factors for the presence of aneurysms, the presence of multiple aneurysms may also increase with age. Familial preponderance is another risk factor for the presence of aneurysms. Familial subarachnoid haemorrhage (SAH) occurs at an earlier age than sporadic SAH, and a higher frequency of multiple aneurysms has been suggested in familial SAH. This may imply that the multiplicity of aneurysms is associated with younger age. We studied the relation between age and the number of aneurysms in patients with SAH. METHODS: From our database we selected patients with aneurysmal SAH admitted between 1985 and 1999. Inclusion criteria were: (1) both carotid and vertebral arteries had been visualised; (2) at least one aneurysm was found, and (3) admission within 72 h after onset of symptoms. For the 555 patients included we recorded the age, sex and number of aneurysms. The patients were categorised into patients with a single aneurysm, patients with more than one aneurysm and those with more than two aneurysms. For all categories we calculated the proportion of patients younger than the median age and the differences between these proportions, with corresponding 95% confidence intervals (CI). We also calculated relative risks (RR) of multiple aneurysms for gender and age below the median. RESULTS: 485 patients had a single aneurysm, and 70 patients had more than one aneurysm. The proportion of patients younger than the median age (51 years) with one aneurysm was 47.8%, for more than one aneurysm 61.4% (difference 13.6%; 95% CI 1.4-25.8), and for more than two aneurysms 82.6% (difference 34.8%, 95% CI 18.7-50.9). The RR of women for multiple aneurysms was 1.52 (95% CI 0.61-3.77), and that of age below the median 4.86 (95% CI 1.68-14.1). CONCLUSIONS: Patients with multiple aneurysms are younger than patients with a single aneurysm. This may suggest that atherosclerotic risk factors are less important than genetic factors in the development of multiple aneurysms.