Abstract: ObjectiveTo determine the diurnal variation,moon phase,and seasonal variation in the onset of stroke. MethodsThe time parameters,including the time,the moon phase and the season of the stroke occurrence for 905 in-patients from 1989-2001 were investigated.ResultsThere was a significant difference (D=0.155,P<0.01) for circadian rhythm in the onset of 321 cases with cerebral infarction,and the incidence frequency at dawn was much higher than that at other time,but the difference of the moon phase and seasonal rhythm in the onset of cerebral infarction were not significant(P>0.05).There were not diurnal variation,moon phase and seasonal rhythms in the onset for cerebral haemorrhage(P>0.05).ConclusionsThe cerebral infarction occur more frequently at dawn time.

Key words: stroke, onset, circadian rhythm, moon phase rhythm, seasonal rhythm