Seasonal variation in ischaemic stroke frequency in Podlaskie Province by season.

PURPOSE The aim of the present study was to assess seasonal differences in ischaemic stroke among patients hospitalized in Department of Neurology in Białystok during 2002-2005. MATERIAL AND METHODS To examine the seasonal incidence of ischaemic stroke, we analyzed data from the Department of Neurology in Białystok in a retrospective study. The year was divided into four seasons: spring (March, April, May), summer (June, July, August), autumn (September, October, November), and winter (December, January, February). Seasonal differences were studied in relation to the following clinical characteristics: age, gender, history of stroke, and time of stroke onset. RESULTS Age of patients with ischaemic stroke ranged 19 between 101 years, a mean age was 72.4 +/- 12 years. Incidence of ischaemic stroke increased in the last years. We noted a higher incidence of ischaemic stroke in older patients (mean 74.36 years old) during winter months than in patients (71.40 years) in summer months. Gender had no effect on incidence of ischaemic stroke. Significant seasonal variation of ischaemic stroke in all years (p = 0.0010) and for 2005 year (0.0090) were found. Incidence of ischaemic stroke was depend on month of year. Significant increase of ischaemic stroke was noted in December. The lowest incidence of stroke was observed in August and September. CONCLUSION Incidence of ischaemic stroke increased in the last years. The present findings suggest an increase in the incidence of ischaemic stroke in winter in December.