Wind-chill and the seasonal variation of cerebrovascular disease.

The hospital admission rates for patients with specific types of stroke were examined for seasonal variation and correlation with meteorological factors. A seasonal variation in admission rates was found for subarachnoid haemorrhage, thrombo-embolic brain infarction and ill-defined cerebrovascular disease. Overall this seasonality was more strongly associated with the computed chilling effect of the atmosphere than with changes in temperature, humidity or wind speed alone. No seasonal variation was observed for admission rates of intracerebral haemorrhage, transient ischaemic attack or occlusion of precerebral arteries. Intracerebral haemorrhage admission rates exhibited a decrease with time. This evidence suggests that seasonal variation in admission rates exists only for certain pathological types of stroke and this is strongly associated with changes in the chilling effect of the atmosphere.