Impact of Cold Spells on Ischemic Stroke Severity and Clinical Outcomes in Tianjin, China

There are several studies on the impact of extreme weather on the incidence and mortality of stroke, but the research on the effect of extreme weather events on severity and outcome of ischemic stroke is scarce. This study aimed to evaluate the impact of cold spells on the severity and clinical outcomes of patients with initial acute ischemic stroke in a hospital-based study. We enrolled 553 patients with initial ischemic stroke during the cold seasons between 2016 and 2019. Patients were separated into the mild stroke group and moderate-to-severe stroke group according to the National Institutes of Health Stroke Scale (NIHSS) of the U.S., and good outcome group and poor outcome group according to modified Rankin Scale (mRS) scores. There are nine different definitions of cold spells according to intensities and duration time. After adjustment for climate factors, air quality index, and common risk factors, it is found that cold spells were associated with moderate-to-severe neurological deficits and clinical outcomes in overall ischemic stroke patients. Furthermore, the delay effect for stroke severity started at the beginning of the cold wave (Lag 0) and lasted up to 14 days (Lags 0–14). In addition, when a cold spell was set as a daily mean temperature < 3rd or 5th percentile and with a duration ≥ 2 or 3 consecutive days, cold spells had a significant impact on clinical outcomes, and there was a definite delay effect of at least 7 days (Lags 0–7) and it lasted up to 14 days (Lags 0–14). At last, we concluded that cold spells may be a contributory factor for more severe neurological deficits and worse outcomes in patients with initial ischemic stroke.