Seasonal variation of aneurysmal subarachnoid haemorrhage.

In a prospective consecutive series of 1,076 patients with aneurysmal subarachnoid haemorrhage (SAH) admitted to the 6 Danish neurosurgical departments in the 5-year period April 1, 1978 to March 31, 1983 a significantly higher seasonal incidence of SAH was seen during spring and autumn compared to summer and winter. No significant seasonal differences in monthly mortality or between females and males were registered. Contrary to several other studies concerning cerebral apoplexy excluding SAH no explanation to the seasonal variation was obtained from differences in weather conditions. A correlation between seasonal variation of aneurysm rupture and physical activity is possible.