Background The goal of the study was to analyse retrospectively the impact of risk factors for subarachnoid haemorrhage (SAH) on the size of ruptured intracranial aneurysms in order to identify variables that might influence the discrepancy between average sizes of ruptured and unruptured aneurysms.

Methods The records and angiographies of 373 patients treated at our centre due to aneurysmal SAH between 2004 and December 2008 were retrospectively analysed. Modifiable and non-modifiable risk factors for SAH were correlated with exact measurement of aneurysm size using three-dimensional rotational digital subtraction angiographies (3D-DSA).

Results Average maximum aneurysm diameter in patients with combined history of hypertension and cigarette smoking was 5.47±3.22 mm (95% CI 4.71 to 6.24); thus, significantly smaller (p<0.001) than in patients with hypertension only (6.27±3.28 mm, 95% CI 5.75 to 6.78), with cigarette smoking only (7.61±4.29 mm, 95% CI 6.43 to 8.79) and patients with no history for risk factors (8.08±4.73 mm, 95% CI 6.96 to 9.21). Odds ratio (OR) for aneurysm size less than 7 mm in patients with combined hypertension and cigarette smoking was 3.63 (95% CI 1.78 to 7.42), 3.09 (95% CI 1.95 to 4.92) in patients with hypertension only and 1.02 (95% CI 0.64 to 1.62) in patients with cigarette smoking only.

Conclusions The present analysis demonstrates a distinct correlation between hypertension, smoking and the size of ruptured aneurysms in SAH patients. Arterial hypertension and cigarette smoking appear to destabilise cerebral aneurysms' growth. Our data strongly suggest that these factors should also be considered when treatment indications for small unruptured aneurysms are discussed.