The effects of heatwaves and cold spells on patients admitted with acute ischemic stroke

The association between short-term apparent temperature exposure and human coagulation: A time-series study from Beijing, 2014-2023

A growing body of evidence suggests that non-optimal ambient temperatures are associated with increased incidence rate and mortality of thromboembolic diseases. We aim to investigate the association between apparent temperature (AT) and coagulation, which is a central pathological link in the formation of thrombi. In this study, we conducted a time series analysis using data from 18,894 participants collected from a health check-up center in Beijing between 2014 and 2023, and validated our findings using 20,549 participants from an andrology outpatient clinic. The daily mean AT was calculated using data on ambient temperature, relative humidity, and wind speed from Beijing. Participants were matched to the lagged moving average of AT (0-7 days) based on their specific health examination dates. The study employed generalized additive models to analyzed the linear and nonlinear associations between AT and coagulation indices. The results indicated that heat resulted in shortened prothrombin time and activated partial thromboplastin time, whereas cold resulted in shortened thrombin time. Fibrinogen showed an increase at both high and low temperatures. Logistic regression analysis revealed that the risk of hypercoagulable state increased in both high and low temperature environments compared to moderate temperatures, with a significant increase observed under extreme heat conditions. Subgroup analyses by sex and age, sensitivity analyses, and the external validation indicated that the association between AT and coagulation was robust. The findings support that both cold and heat can augment blood coagulability through distinct stages of the coagulation cascade, thereby leading to an elevated risk of thromboembolic diseases.

Impact of Ambient Air Pollution with PM2.5 on Stroke Occurrence: Data from Kaunas (Lithuania) Stroke Register (2010–2022)

Background: Ambient particulate matter of ≤2.5 μm in diameter (PM2.5) is named as a risk factor for cerebrovascular diseases. This investigation aimed to evaluate the impact of ambient air pollution with PM2.5 on stroke occurrence. Methods: The study was performed in Kaunas, Lithuania, from 2010 to 2022. The daily numbers of ISs, subarachnoid hemorrhages (SAHs), and intracerebral hemorrhages (ICHs) were obtained from the Kaunas Stroke Register. The association between stroke occurrence and PM2.5 exposure was assessed by time- and seasonally stratified Poisson regression. Results: Among middle-aged persons, 3377 had a stroke, of which 2686 (79.5%) had an IS, 469 (13.9%) had an ICH, and 222 (6.6%) had SAH. The relative risk (RR) of SAH was increased by 1.7% with an increase in daily PM2.5 by 1 μg/m3 on the same day and at a lag of 1 day, and by 2.2% with an increase in mean PM2.5 concentration at a lag 0–1 days by 1 μg/m3. The RR of having a SAH was increased by 0.7% with an increase in daily PM2.5 by 1 μg/m3 on the same day. Conclusions: Significant associations between stroke occurrence and air pollution with PM2.5 were found in the SAH and HS patients, and only in middle-aged subjects.

High average daily temperature in summer and the incidence of thrombolytic treatment for acute ischemic stroke

INTRODUCTION

Meteorological factors can increase stroke risk; however, their impact is not precisely understood. Heat waves during summer increase total mortality. Therefore, we hypothesized that the average daily temperature in summer may correlate with the incidence of thrombolytic treatment for acute ischemic stroke in Budapest and Pest County, Hungary.

METHODS

We analyzed the relationship between the average daily temperature in summer months and the daily number of thrombolytic treatments (TT) performed with the indication of acute ischemic stroke between 1st June and 31st August each year from 2007 to 2016. The analysis was also performed after the omission of the data of the last day of the months due to possible psychosocial impact reported in our previous study. Spearman's correlation was used for statistical analysis.

RESULTS

No significant correlation was found between the average summer daily temperature and the number of TT in the entire sample of the 10-year period. When omitting the data of the last day of each month, positive correlations were suspected in 2014 (r=0.225, P=0.034) and 2015 (r=0.276, P=0.009).

CONCLUSION

Our findings did not confirm an association between the average daily temperature in summer and the daily number of TT throughout the examined 10-year period. However, importantly, in 2014 and 2015, the years with the highest average daily temperatures in this period, a positive correlation was found. The level of correlation is modest, indicating that risk factors, both meteorological and non-meteorological, other than the average temperature, play equally important roles in determining the incidence of thrombolytic treatment for acute ischemic stroke on the population level.

Neurological patients confronting climate change: A potential role for the glymphatic system and sleep

Interest in the health consequences of climate change (global warming, heatwaves) has increased in the neurological community. This review addresses the impact of elevated ambient temperatures and heatwaves on patients with neurological and mental health disorders, including multiple sclerosis, synucleinopathies, dementia, epilepsies, mental health, and stroke. Patients with such conditions are highly vulnerable during heatwaves because of functional disorders affecting sleep, thermoregulation, autonomic system reactivity, mood, and cognitive ability. Several medications may also increase the risk of heatstroke. Special attention is devoted to the involvement of common underlying mechanisms, such as sleep and the glymphatic system. Disease prevention and patient care during heatwaves are major issues for caregivers. Beyond the usual recommendations for individuals, we favor artificially induced acclimation to heat, which provides preventive benefits with proven efficacy for healthy adults.

Low ambient temperature exposure increases the risk of ischemic stroke by promoting platelet activation

BACKGROUND

Accumulating epidemiological evidence suggests the association between low ambient temperature exposure and the risk of ischemic stroke, but the underlying mechanisms remain unclear.

OBJECTIVE

Given the crucial role of platelet activation and thrombosis in ischemic stroke, this study aims to investigate the effect of ambient temperature on platelet activation through multi-center clinical data in Tianjin as well as animal experiments.

METHODS

From 2018 to 2020, nearly 3000 ischemic stroke patients from three stroke centers in Tianjin were included in the analysis, among them the ADP induced platelet aggregation rate was available. Meteorological data from the same period had also been collected. After controlling for confounding factors, the generalized additive mixed model (GAMM) was used to evaluate the correlation between environmental temperature and platelet aggregation rate. In further animal experiments, platelet function assessments were conducted on mice from the cold exposure group and the normal temperature group, including platelet aggregation, spreading, and clot retraction. Additionally, tail bleeding and mesentery thrombosis were also tested to monitor hemostasis and thrombosis in vivo.

RESULT

A nonlinear "S" shaped relationship between outdoor temperature and platelet aggregation was found. Each 1 °C decrease of mean temperature was associated with an increase of 7.77 % (95 % CI: 2.06 % - 13.48 %) in platelet aggregation. The ambient temperature is not related to other platelet parameters. Subgroup analysis found that males, people aged ≥65 years, and hypertensive individuals are more susceptible to temperature changes. Furthermore, animal experiments demonstrated that the increased CIRBP levels and subsequent activation of p-AKT/p-ERK may be one of the reasons for cold exposure induced platelets activation.

CONCLUSION

Both clinical data and basic research support that low ambient temperature exposure has the potential to increase platelet activation. These results provide a basis for understanding the potential mechanism of temperature variations on the pathogenesis of cerebrovascular diseases.

Risk and attributable fraction estimation for the impact of exposure to compound drought and hot events on daily stroke admissions

BACKGROUND

The projection indicates that compound drought and hot events (CDHEs) will intensify, posing risks to cardiovascular health by potentially increasing stroke incidents. However, epidemiological evidence on this topic remains scarce. This study investigates the association between exposure to CDHEs and the risk of daily stroke admissions, specifically examining the effects on various stroke categories such as Subarachnoid Hemorrhage (SAH), Intracerebral Hemorrhage (ICH), Ischemic Stroke (IS), Transient Ischemic Attack (TIA), and other types of stroke.

METHODS

Data on daily stroke admissions from 2010 to 2015 were obtained from the Urban Employee Basic Medical Insurance (UEBMI) and Urban Resident Basic Medical Insurance (URBMI) claims databases in Guangzhou, China. Hot events were identified as days when the daily mean temperature exceeded the 75th percentile during the warm season (May to October) over the study period. The Standardized Precipitation Evapotranspiration Index (SPEI) was utilized to identify drought conditions, with thresholds set at -1 and -1.5 for low-severity and high-severity drought events, respectively. Through a generalized additive model (GAM), we analyzed the cumulative effects of CDHE exposure on daily stroke admissions and calculated the Attributable Fraction (AF) related to CDHEs.

RESULTS

The analysis included 179,963 stroke admission records. We observed a significant increase in stroke admission risks due to exposure to hot events coupled with high-severity drought conditions (RR = 1.18, 95%CI: 1.01-1.38), with IS being the most affected category (RR = 1.20, 95%CI: 1.03-1.40). The AF of total stroke admission attributed to hot events in conjunction with high-severity drought conditions was 24.40% (95%CI: 1.86%-50.20%).

CONCLUSION

The combination of hot events with high-severity drought conditions is likely linked to an increased risk of stroke and IS admissions, which providing new insights into the impact of temperature and climate-related hazards on cardiovascular health.

Short-term effects of heatwaves on clinical and subclinical cardiovascular indicators in Chinese adults: A distributed lag analysis

AIMS

Previous studies have related heat waves to morbidity and mortality of cardiovascular diseases; however, potential mechanisms remained limited. Our aims were to investigate the short-term effects of heat waves on a series of clinical/subclinical indicators associated with cardiovascular health.

METHODS

Our study used 80,574 health examination records from the Health Management Center of Nanjing Zhongda Hospital during the warm seasons of 2019-2021, including 62,128 participants. A total of 11 recognized indicators of cardiovascular risk or injury were assessed. Air pollution and meteorological data were obtained from the Nanjing Ecological Environment Bureau and the China Meteorological Data Network, respectively. Heat waves were defined as a daily average temperature over the 95th percentile for three or more consecutive days from May to September. We used a combination of linear mixed effects models and distributed lag nonlinear models to assess the lagged effects of heat waves on clinical and subclinical cardiovascular indicators. Stratified analyses based on individuals' characteristics, including gender, age, body mass index (BMI), diabetes, and hypertension, were also performed.

RESULTS

Heat waves were related to significant changes in most indicators, with the magnitude of effects generally peaking at a lag of 0 to 3 days. Moreover, the cumulative percentage changes over lag 0-7 days were -0.82 % to -2.55 % in blood pressure, 1.32 % in heart rate, 0.20 % to 2.66 % in systemic inflammation markers, 0.36 % in a blood viscosity parameter, 9.36 % in homocysteine, and 1.35 % to 3.25 % in injuring myocardial enzymes. Interestingly, females and males showed distinct susceptibilities in different indicators. Stronger effects were also found in participants aged 50 years or over, individuals with abnormal BMI status, and patients with diabetes.

CONCLUSION

Short-term exposure to heat waves could significantly alter clinical/subclinical cardiovascular indicator profiles, including blood pressure changes, increased heart rate, acute systemic inflammation, elevated blood viscosity, and myocardial injury.

The Impact of Weather and Mode of Transport on Outcomes of Patients With Acute Ischemic Stroke Undergoing Mechanical Thrombectomy

BACKGROUND

Efficient transfer to mechanical thrombectomy (MT)-capable centers is essential for patients with stroke. Weather may influence stroke risk, transportation, and outcomes.

OBJECTIVE

To investigate how weather affects stroke patient transfer and outcomes after MT.

METHODS

We retrospectively collected data for patients with stroke transferred from spoke to our hub hospital to undergo MT between 2017 and 2021. We examined associations between weather, transportation, and patient outcomes.

RESULTS

We included 543 patients with a mean age of 71.7 years. The median National Institutes of Health Stroke Score increased from 14 to 15 after transportation. The median modified Rankin Scale was 4 at discharge and 90 days, and 3 at the final follow-up (mean 91.7 days). Higher daily temperatures were associated with good outcome, whereas daily drizzle was associated with poor outcome. More patients were transferred by air when visibility was better, and by ground during heavier precipitation, higher humidity, rain, mist, and daily drizzle, fog, and thunder . Patient outcomes were not associated with transportation mode. Among the independent predictors of good outcome, none was a weather variable. Lower hourly relative humidity ( P = .003) and longer road distance ( P < .001) were independent predictors of using air transportation, among others.

CONCLUSION

During transportation, higher temperature was associated with good outcome, whereas daily drizzle was associated with poor outcome after MT. Although weather was associated with transportation mode, no differences in outcomes were found between transportation modes. Further studies are needed to modify transfer protocols, especially during cold and rainy days, and potentially improve outcomes.

Ambient temperature and ambulatory blood pressure: An hourly-level, longitudinal panel study

BACKGROUND

Variations of blood pressure (BP) related to air temperature have been reported previously; however, no evidence is available regarding the association of hourly ambient temperature with ambulatory blood pressure.

METHODS

We conducted a longitudinal panel study among 1895 patients from an outpatient department who received repeated ambulatory blood pressure monitoring in Urumqi, China between July 2020 and December 2021. We obtained hourly ambient temperature from the nearest monitoring station to the residential address, and measured 4 ambulatory blood pressure indicators. Linear mixed-effect model combined with distributed lag models were applied to investigate the cumulative associations of hourly temperature with BP.

RESULTS

A total of 97,466 valid blood pressure measurements were evaluated. We observed almost linear and monotonically decreasing relationships between temperature and blood pressure. The effects occurred in the same hour, attenuated thereafter and became insignificant approximately 36 h. A 10 °C decrease in temperature was significantly associated with increments of 0.84 mmHg in systolic blood pressure, 0.56 mmHg in diastolic blood pressure, 1.38 mmHg in mean arterial pressure, and 0.66 mmHg in pulse pressure over lag 0 to 36 h. Stronger associations were found among patients of female sex, age between 18 and 65 years, overweight or obesity, minority, less education or in the cold season, as well as those without hypertension or with coronary heart disease, or did not take anti-hypertension medication.

CONCLUSION

Our study provides robust evidence that hourly ambient temperature is inversely associated with ambulatory blood pressure. It also highlights a linear relationship between decreased ambient temperature and elevated BP, which may have implications for the prevention and management of hypertension in susceptible populations.

Temperature variability increases the onset risk of ischemic stroke: A 10-year study in Tianjin, China

Background

Epidemiological evidence suggests a correlation between ambient temperature and ischemic stroke. However, evidence on the impact of daily temperature variability on the onset of ischemic stroke is lacking and limited.

Objective

We aimed to investigate the short-term association between temperature variability and ischemic stroke occurrence in Tianjin.

Methods

We performed a 10-year analysis of ischemic stroke patients hospitalized in two affiliated hospitals of Tianjin Medical University from 2011 to 2020. Daily meteorological data were collected from the Tianjin Meteorological Bureau. Temperature variability was calculated from the standard deviation (SD) of daily minimum and maximum temperatures over exposure days. A quasi-Poisson generalized linear regression combined with distributed lag non-linear model (DLNM) was used to estimate the effect of temperature variability on daily stroke onset, while controlling for daily mean temperature, relative humidity, long-term trend and seasonality, public holiday, and day of the week.

Results

Temperature variability was positively associated with ischemic stroke. A 1°C increase in temperature variability at 0-1 days (TV_0-1) was associated with a 4.1% (1.9-6.3%) increase of ischemic stroke onset. In a stratified analysis, men, people aged ≤65 years, and individuals with pre-existing hypertension, hyperlipidemia, hyperhomocysteinemia were more susceptible to temperature variability. Furthermore, the influence pattern of temperature variability on ischemic stroke was different in the cold season (November-April) and the warm season (May-October).

Conclusion

Our findings suggested that short-term temperature variability exposure could increase the risk of ischemic stroke, which may provide new insights into the impact of climate change on health.

The underlying mechanisms of cold exposure-induced ischemic stroke

Growing evidence suggests that cold exposure is to some extent a potential risk factor for ischemic stroke. At present, although the mechanism by which cold exposure induces ischemic stroke is not fully understood, some potential mechanisms have been mentioned. First, the seasonal and temperature variability of cerebrovascular risk factors (hypertension, hyperglycemia, hyperlipidemia, atrial fibrillation) may be involved. Moreover, the activation of sympathetic nervous system and renin-angiotensin system and their downstream signaling pathways (pro-inflammatory AngII, activated platelets, and dysfunctional immune cells) are also major contributors. Finally, the influenza epidemics induced by cold weather are also influencing factors that cannot be ignored. This article is the first to systematically and comprehensively describe the underlying mechanism of cold-induced ischemic stroke, aiming to provide more preventive measures and medication guidance for stroke-susceptible individuals in cold season, and also provide support for the formulation of public health policies.