Seasonal and Monthly variation in stroke and its subtypes–10 Year Hospital-Based Study

BACKGROUND AND OBJECTIVES There is no evidence of long-term studies of seasonal variations in stroke in Iran. Hence, the aim of this study was to determine the seasonal and monthly variation of 28-day mortality in Isfahan, Iran. METHODS From 2003 to 2013, In a Hospital-based retrospective study, 24186 cases with first-ever stroke were analyzed in Isfahan. Multinomial logistic regression was used to calculate odds ratios (OR) with 95% confidence intervals (CI) for seasonal and monthly 28-day mortality for stroke in general and three subtypes of stroke including intracranial hemorrhage (ICH), ischemic (IS) and subarachnoid hemorrhage (SAH). RESULTS In this study, unadjusted and adjusted odds ratios of seasonal 28-day mortality of stroke was highest in the winter and lowest in the summer. Although, differences were not statistically significant. For total and IS stroke, the unadjusted 28-day mortality ratio (UMR) was significant in February (1.19, 95% CI 1.00 -1.42, P= 0.04) as compared to March. Whereas after adjusted, for total stroke, 28-day mortality was significantly lowest in May (0.746, 95% CI 0.575-0.97, p=0.029), June (0.777, 95% CI 0.60-0.99, p=0.49) and July (0.771, 95% CI 0.59-0.99 p=0.049) as compared to March. The AMR between months were not significant in SAH and IS. CONCLUSION Our findings demonstrate clear obvious monthly variation of 28-day mortality of stroke and its subtypes in Isfahan but no seasonal variations were observed.