COLD - A RISK FACTOR FOR STROKE

A retrospective study was performed to investigate seasonal variation in stroke incidence and to evaluate the hypothesis that cold might be a risk factor. Data were obtained from the central registry of the Hos pital de S. Joao, Porto, Portugal, concerning 4048 patients consecutiv ely admitted for cerebrovascular disease during a period of 33 months. Monthly admissions for stroke and its subtypes were related to mean v alues of ambient temperature using linear correlation. There was a str ong inverse correlation between average temperature and total admissio ns for cerebrovascular disease (r = -0.72, P < 0.00005), intracerebral haemorrhage (r = -0.66, P < 0.00005), ischaemic stroke (r = -0.46, P = 0.007) and transient ischaemic attack (r = -0.41, P = 0.017). These correlations were independent of any seasonal variation in the number of hospital admissions due to all causes. No relation was found betwee n temperature and subarachnoid haemorrhage. The rhythmometric analysis showed the presence of a statistically significant rhythm with an acr ophase in the coldest months. These results support the hypothesis of stroke being a chronorisk disease to which cold might represent a trig gering factor.