Seasonality of stroke in Finland

Introduction: The burden of stroke is increasing globally. Reports on seasonal variations in stroke occurrence are conflicting and long-term data are absent.
Methods: A retrospective cohort study using discharge registry data of all acute stroke admissions in Finland during 2004–2014 for patients ≥18 years age. A total of 97,018 admissions for ischemic stroke (IS) were included, 18,252 admissions for intracerebral hemorrhage (ICH) and 11,271 admissions for subarachnoid hemorrhage (SAH).
Results: The rate of IS admissions increased (p = 0.025) while SAH admission rate decreased (p < 0.0001), and ICH admission rate remained stable during the study period. The lowest seasonal admission rates were detected in summer and the highest in autumn for all stroke subtypes. Seasonal variation of IS was more pronounced in men (p = 0.020), while no sex difference was detected in ICH or SAH. The seasonal patterns of in-hospital mortality and length of stay (LOS) differed markedly by stroke subtype. Diagnoses of hypertension, atrial fibrillation, or diabetes showed no seasonality.
Conclusions: All major stroke subtypes occurred most commonly in autumn and most infrequently in summer. Seasonality of in-hospital mortality and length of hospital stay appears to vary by stroke subtype. The seasonal pattern of ischemic stroke occurrence appears to have changed during the past decades.Key messages
All major stroke subtypes (ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage) occurred most frequently in autumn and least frequently in summer.
Seasonal patterns of in-hospital mortality and length of stay differed markedly by stroke subtype.
The seasonal pattern of ischemic stroke occurrence in Finland seems to have changed compared to 1982–1992.

All major stroke subtypes (ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage) occurred most frequently in autumn and least frequently in summer.
Seasonal patterns of in-hospital mortality and length of stay differed markedly by stroke subtype.
The seasonal pattern of ischemic stroke occurrence in Finland seems to have changed compared to 1982–1992.

研究背景：全球脑卒中负担正日益加重。现有关于脑卒中发病季节变异性的研究结论存在分歧，且缺乏长期相关数据。
研究方法：本研究为回顾性队列研究，采用芬兰2004年至2014年所有18岁及以上急性脑卒中住院患者的出院登记数据。最终纳入缺血性脑卒中（ischemic stroke, IS）住院病例97018例、脑出血（intracerebral hemorrhage, ICH）住院病例18252例，以及蛛网膜下腔出血（subarachnoid hemorrhage, SAH）住院病例11271例。
研究结果：研究期间，缺血性脑卒中住院率呈上升趋势（p=0.025），蛛网膜下腔出血住院率呈下降趋势（p<0.0001），而脑出血住院率维持稳定。所有脑卒中亚型的住院率均在夏季最低、秋季最高。男性缺血性脑卒中的季节变异性更为显著（p=0.020），而脑出血与蛛网膜下腔出血未观察到性别差异。住院死亡率与住院时长（length of stay, LOS）的季节模式随脑卒中亚型不同存在显著差异。高血压、心房颤动或糖尿病的诊断未表现出季节相关性。
研究结论：所有主要脑卒中亚型均以秋季最为高发、夏季最为低发。住院死亡率与住院时长的季节模式随脑卒中亚型不同存在显著差异。缺血性脑卒中发病的季节模式在过去数十年间已发生改变。
核心结论
所有主要脑卒中亚型（缺血性脑卒中、脑出血、蛛网膜下腔出血）均以秋季最为高发、夏季最为低发。
住院死亡率与住院时长的季节模式随脑卒中亚型不同存在显著差异。
相较于1982年至1992年，芬兰缺血性脑卒中发病的季节模式已发生改变。

所有主要脑卒中亚型（缺血性脑卒中、脑出血、蛛网膜下腔出血）均以秋季最为高发、夏季最为低发。
住院死亡率与住院时长的季节模式随脑卒中亚型不同存在显著差异。
相较于1982年至1992年，芬兰缺血性脑卒中发病的季节模式已发生改变。