Meteorological factors and aneurysmal subarachnoid haemorrhage in Hong Kong.

To evaluate the influence of meteorological factors on the onset of aneurysmal subarachnoid haemorrhage in Hong Kong.Retrospective review of prospectively collected data.University teaching hospital, Hong Kong.A total of 135 consecutive patients with acute aneurysmal subarachnoid haemorrhage presenting to the hospital within 48 hours after ictus from October 2002 to October 2006.Occurrence of aneurysmal subarachnoid haemorrhage in relation to daily changes in atmospheric pressure, temperature, and humidity.The peak incidence of aneurysmal subarachnoid haemorrhage occurred in winter (December to February), especially January. The mean (+/-standard deviation) daily atmospheric pressure change was significantly higher on days with aneurysmal subarachnoid haemorrhage onset as opposed to days without (1.75+/-1.47 hPa vs 1.48+/-1.28 hPa; P=0.032).A seasonal variation and relationship to atmospheric pressure change in aneurysmal subarachnoid haemorrhage was noted in the current study carried out in Hong Kong. The mechanism linking atmospheric pressure change and aneurysmal rupture remained to be explored.