Seasonal variation in the occurrence of ischemic stroke: A meta-analysis

Viral Infection and Ischemic Stroke: Emerging Trends and Mechanistic Insights

Population studies have suggested that viral infections may be contributing to risk of ischemic stroke, although the mechanisms for this are unclear. In this review, we examine the epidemiological evidence supporting the involvement of viral diseases, including influenza, COVID-19, chronic herpesvirus infections, and hepatitis C in current trends of stroke incidence. To support these associations, we highlight the virus-host interactions that are critical in the context of stroke, including direct effects of acute and persistent viral infections on vascular function, inflammation, and thrombosis. Additionally, we evaluate the systemic changes that occur during viral infection that can predispose individuals to ischemic stroke, including alterations in blood pressure regulation, coagulation, and lipid metabolism. Our review emphasizes the need to further elucidate precise mechanisms involved in viral infections and stroke risk. Future research will inform the development of targeted interventions for stroke prevention in the context of viral diseases.

Impact of seasonal blood pressure changes on visit-to-visit blood pressure variability and related cardiovascular outcomes

BACKGROUND

Visit-to-visit blood pressure (BP) variability associates with an increased risk of cardiovascular events. We investigated the role of seasonal BP modifications on the magnitude of BP variability and its impact on cardiovascular risk.

METHODS

In 25 390 patients included in the ONTARGET and TRANSCEND trials, the on-treatment systolic (S) BP values obtained by five visits during the first two years of the trials were grouped according to the month in which they were obtained. SBP differences between winter and summer months were calculated for BP variability quintiles (Qs), as quantified by the coefficient of variation (CV) of on-treatment mean SBP from the five visits. The relationship of BP variability with the risk of cardiovascular events and mortality was assessed by the Cox regression model.

RESULTS

SBP was approximately 4 mmHg lower in summer than in winter regardless of confounders. Winter/summer SBP differences contributed significantly to each SBP-CV quintile. Increase of SBP-CV from Q1 to Q5 was associated with a progressive increase in the adjusted hazard ratio (HR) of the primary endpoint of the trials, i.e. morbid and fatal cardiovascular events. This association was even stronger after removal of the effect of seasonality from the calculation of SBP-CV. A similar trend was observed for secondary endpoints.

CONCLUSIONS

Winter/summer SBP differences significantly contribute to visit-to-visit BP variability. However, this contribution does not participate in the adverse prognostic significance of visit-to-visit BP variations, which seems to be more evident after removal of the BP effects of seasonality from visit-to-visit BP variations.

Seasonal Variations in Stroke and a Comparison of the Predictors of Unfavorable Outcomes among Patients with Acute Ischemic Stroke and Cardioembolic Stroke

We investigated the seasonal variations in stroke in 4040 retrospectively enrolled patients with acute ischemic stroke (AIS) admitted between January 2011 and December 2022, particularly those with cardioembolic (CE) stroke, and compared predictors of unfavorable outcomes between AIS patients and CE stroke patients. The classification of stroke subtypes was based on the Trial of ORG 10172 in Acute Stroke Treatment. Stroke occurrence was stratified by seasons and weekdays or holidays. Of all AIS cases, 18% were of CE stroke. Of all five ischemic stroke subtypes, CE stroke patients were the oldest; received the most thrombolysis and thrombectomy; had the highest initial National Institutes of Stroke Scale (NIHSS) and discharge modified Rankin Scale (mRS) scores; and had the highest rate of in-hospital complications, unfavorable outcomes (mRS > 2), and mortality. The highest CE stroke prevalence was noted in patients aged ≥ 85 years (30.9%); moreover, CE stroke prevalence increased from 14.9% in summer to 23.0% in winter. The main predictors of death in patients with CE stroke were age > 86 years, heart rate > 79 beats/min, initial NIHSS score > 16, neutrophil-to-lymphocyte ratio (NLR) > 6.4, glucose > 159 mg/dL, cancer history, in-hospital complications, and neurological deterioration (ND). The three most dominant factors influencing death, noted in not only patients with AIS but also those with CE stroke, are high initial NIHSS score, ND, and high NLR. We selected the most significant factors to establish nomograms for predicting fatal outcomes. Effective heart rhythm monitoring, particularly in older patients and during winter, may help develop stroke prevention strategies and facilitate early AF detection.

Clustering of Environmental Parameters and the Risk of Acute Ischaemic Stroke

Acute ischaemic stroke (AIS) risk on days with similar environmental profiles remains unknown. We investigated the association between clusters of days with similar environmental parameters and AIS incidence in Singapore. We grouped calendar days from 2010 to 2015 with similar rainfall, temperature, wind speed, and Pollutant Standards Index (PSI) using k-means clustering. Three distinct clusters were formed 'Cluster 1' containing high wind speed, 'Cluster 2' having high rainfall, and 'Cluster 3' having high temperatures and PSI. We aggregated the number of AIS episodes over the same period with the clusters and analysed their association using a conditional Poisson regression in a time-stratified case-crossover design. Comparing the three clusters, Cluster 3 had the highest AIS occurrence (IRR 1.09; 95% confidence interval (CI) 1.05-1.13), with no significant difference between Clusters 1 and 2. Subgroup analyses in Cluster 3 showed that AIS risk was amplified in the elderly (≥65 years old), non-smokers, and those without a history of ischaemic heart disease/atrial fibrillation/vascular heart disease/peripheral vascular disease. In conclusion, we found that AIS incidence may be higher on days with higher temperatures and PSI. These findings have important public health implications for AIS prevention and health services delivery during at-risk days, such as during the seasonal transboundary haze.

Acute ischemic stroke and COVID-19 pandemic in Brazil: a comparative study of frequency and risk factors before and during SARS-CoV-2 era

Background

COVID-19 pandemic directly impacted the request for hospital care and medical assistance for several diseases worldwide, as occurred with acute ischemic stroke. The present study sought to compare the incidence and severity of acute ischemic stroke (AIS), in addition to sociodemographic, clinical, and radiological characteristics of patients hospitalized in the prepandemic (2018–2019) and pandemic (2020–2021) eras.

Methods

An incidence case–control, observational, and analytical research was carried out in the Stroke Unit of Hospital Governador Celso Ramos, Florianopolis, Santa Catarina, Brazil, including 171 patients admitted with acute ischemic stroke from April 2018 to April 2019 (prepandemic era) and 148 patients between January 2020 and January 2021 (during pandemic).

Results

The mean incidence of AIS hospital admissions was significantly lower in the pandemic period (CI 95%, 0.2 to 5.6; p = 0.04), being lower in the lockdown periods and when the incidence of new COVID-19 cases increased. Besides, referring to AIS severity, the mean areas of AIS were larger during the pandemic period (p < 0.01), especially in August, September, December, and January (p < 0.05). Sociodemographic and clinical variables did not show any difference between the two periods of the study.

Conclusions

Hospital admissions for AIS decreased in the COVID-19 pandemic, mostly during months of higher incidences of new COVID-19 cases. When the incidence of admissions diminished, an increase in the severity of AIS was observed, characterized by larger areas. These findings might contribute to other similar referral centers in managing public policies related to stroke.

Plasma Proteins as Occupational Hazard Risk Monitors for Populations Working in Harsh Environments: A Mendelian Randomization Study

Harsh work environments can include very cold, hot, dusty, and noisy workplaces, as well as exposure in the workplace with chemicals and other fumes, cigarette smoke, and diesel exhaust. Although working in these harsh environments can have a negative effect on health, there are no effective biomarkers for monitoring health conditions until workers develop disease symptoms. Plasma protein concentrations, which reflect metabolism and immune status, have great potential as biomarkers for various health conditions. Using a Mendelian-randomization (MR) design, this study analyzed the effects of these harsh environments on plasma proteins to identify proteins that can be used as biomarkers of health status. Preliminary analysis using inverse variance weighted (IVW) method with a p-value cutoff of 0.05 showed that workplace environments could affect the concentrations of hundreds of plasma proteins. After filtering for sensitivity via MR-Egger, and Weighted Median MR approaches, 28 plasma proteins altered by workplace environments were identified. Further MR analysis showed that 20 of these plasma proteins, including UNC5D, IGFBP1, SCG3, ST3GAL6, and ST3GAL2 are affected by noisy workplace environments; TFF1, RBM39, ACYP2, STAT3, GRB2, CXCL1, EIF1AD, CSNK1G2, and CRKL that are affected by chemical fumes; ADCYAP1, NRSN1, TMEM132A, and CA10 that are affected by passive smoking; LILRB2, and TENM4 that are affected by diesel exhaust, are associated with the risk of at least one disease. These proteins have the potential to serve as biomarkers to monitor the occupational hazards risk of workers working in corresponding environments. These findings also provide clues to study the biological mechanisms of occupational hazards.

Stroke admissions and revascularization treatments in Denmark during COVID-19

Objective

The aim of this study was to assess the number of stroke‐related admissions and acute treatments during the first two waves of COVID‐19 and lockdowns in the Capital Region of Denmark and the Region of Zealand.

Materials & Methods

The weekly numbers of admitted patients with stroke were retrieved from electronic patient records from January 2019 to February 2021 and analysed to reveal potential fluctuations in patient volumes during the pandemic.

Results

A total of 23,688 patients were included, of whom 2049 patients were treated with tissue‐type plasminogen activators (tPA) and 552 underwent endovascular thrombectomy (EVT). We found a transient decrease in the number of weekly admitted patients (pts/week) with all strokes (−9.8 pts/week, 95% CI: −19.4; −0.2, p = .046) and stroke mimics (−30.1 pts/week, 95% CI: −39.9; −20.3, p < .001) during the first lockdown compared to pre‐COVID‐19. The number of subarachnoid haemorrhage, intracerebral haemorrhage, and ischaemic stroke admissions showed insignificant declines. Analysing all COVID‐19 periods collectively revealed increased volumes of ischaemic stroke (+6.2 pts/week, 95% CI: +1.6; +10.7, p = .009) compared to pre‐COVID levels, while numbers of stroke mimics remained lower than pre‐COVID. Weekly tPA and EVT treatments remained constant throughout the study period.

Conclusions

Our results are comparable with other studies in finding reductions in stroke‐related admissions early in the pandemic. This is the first study to report increased stroke volumes following the first wave of the pandemic. The mechanisms behind the observed drop and subsequent rise in strokes are unclear and warrant further investigation.

Stroke Seasonality and Weather Association in a Middle East Country: A Single Tertiary Center Experience

Background: Stroke is a medical condition that leads to major disability and mortality worldwide. Some evidence suggests that weather and seasonal variations could have an impact on stroke incidence and outcome. However, the current evidence is inconclusive. Therefore, this study examines the seasonal variations and meteorological influences on stroke incidence and outcome in the largest city in Saudi Arabia.

Methods: From February 2016 to July 2019, we retrospectively reviewed data from all patients with acute ischemic (AIS) or hemorrhagic stroke (HS) admitted to the stroke unit in a tertiary academic center in Saudi Arabia. The corresponding daily meteorological data were obtained for the same period. We considered the months from November to March as the cold season and April to October as the hot season.

Results: The final cohort included 1,271 stroke patients; 60.89% (n = 774) cases occurred in the hot season, while 39.1% (n = 497) in the cold season. Males accounted for 69.6% (n = 884) of the cases. The proportion of ischemic stroke was 83.2% [hot season 83.9% (n = 649) vs. cold season 82.3% (n = 409)]. We found no statistically significant difference between seasons (hot or cold) in stroke incidence, severity [National Institutes of Health Stroke Scale (NIHSS)], hospital course (pneumonia, thromboembolism, intensive care stay, or length of stay), or outcome [modified Rankin scale (mRS) on discharge and death].

Conclusions: In Riyadh, Saudi Arabia, our study found no impact of weather or seasonal variations on stroke incidence, hospital course, or outcomes. However, our findings warrant further research in different country regions.

Comparative Analysis of COVID-19 Outbreak and Changes in Neurosurgical Emergency Patients

Objective

COVID-19 has spread worldwide since the first case was reported in Wuhan, China, in December 2019. Our institution is a regional trauma and emergency center in the northern Gyeonggi Province. The changing trend of patient care in the emergency room of this hospital likely reflects the overall trend of patients in the area. In the present study, whether changes in the surrounding social environment following the outbreak of COVID-19 changed the incidence of neurosurgical emergency patients and whether differences in practice existed were investigated.

Methods

The overall trend was analyzed from January 2020 which is before the outbreak of COVID-19 to September 2020. To remove bias due to seasonal variation, the previous 2 year's records during the same period were reviewed and compared. Confirmed COVID-19 patients in the northern Gyeonggi Province were identified using data released by the government. And patients who came to the emergency department with head trauma and stroke were identified.

Results

Based on the present study results, the total number of neurosurgery emergency patients decreased over the study period. In the trauma patient group, the number of patients not involved in traffic accidents significantly decreased compared with patients involved in traffic accidents. Among the stroke cases, the rate of ischemic stroke was lower than hemorrhagic stroke, although a statistically significant difference was not observed. Meanwhile, an increase in the risk of mortality associated with trauma or stroke cases was not observed during the COVID-19 outbreak compared with the same time period in the previous year.

Conclusion

Due to the occurrence of COVID-19, non-essential activities have decreased and trauma cases not associated with traffic accidents appeared to decrease. Due to the decrease in overall activity, the number of stroke patients has also decreased. This trend is expected to continue even in the post-COVID-19 era, and accordingly, the results from the present study are relevant especially if the current situation continues.

Dependence of seasonal dynamics of hemorrhagic and ischemic strokes on the climate of a region: A meta-analysis

BACKGROUND

Cardiovascular events occur more often in winter than in summer; however, the dependence of strokes on various meteorological factors remains unclear.

AIMS

The purpose of this meta-analysis was to determine the dependence of the circannual dynamics of hospitalizations for hemorrhagic stroke and ischemic stroke on seasonal fluctuations in meteorological factors.

SUMMARY OF REVIEW AND CONCLUSIONS

For our meta-analysis, we selected 20 and 26 publications examining the seasonal dynamics of hemorrhagic stroke and ischemic stroke, respectively . The meta-analysis showed that hemorrhagic stroke is less likely to occur in summer than in other seasons and does not depend on a region's climate. The seasonal dynamics of ischemic stroke are not clearly expressed and are determined by the characteristics of a region's climate. In a climate without pronounced seasonal dynamics of atmospheric pressure and in wet winters, the vector of ischemic stroke incidents will not be expressed or slightly shifted toward winter. Low atmospheric pressure in summer is associated with an increased likelihood of ischemic stroke during this season compared to winter. There was also a relation between ischemic stroke risk with high relative humidity and a significant decrease in ρO₂ in summer, but there is not enough evidence regarding this association. We did not reveal dependence of the seasonal dynamics of strokes on the amplitude of annual fluctuations in air temperature.

Decline in mild stroke presentations and intravenous thrombolysis during the COVID-19 pandemic: The Society of Vascular and Interventional Neurology Multicenter Collaboration

BACKGROUND

To evaluate overall ischemic stroke volumes and rates, specific subtypes, and clinical presentation during the COVID-19 pandemic in a multicenter observational study from eight states across US.

METHODS

We compared all ischemic strokes admitted between January 2019 and May 2020, grouped as; March-May 2020 (COVID-19 period) and March-May 2019 (seasonal pre-COVID-19 period). Primary outcome was stroke severity at admission measured by NIHSS stratified as mild (0-7), moderate [8-14], and severe (>14). Secondary outcomes were volume of large vessel occlusions (LVOs), stroke etiology, IV-tPA rates, and discharge disposition.

RESULTS

Of the 7969 patients diagnosed with acute ischemic stroke during the study period, 933 (12 %) presented in the COVID-19 period while 1319 (17 %) presented in the seasonal pre-COVID-19 period. Significant decline was observed in the mean weekly volumes of newly diagnosed ischemic strokes (98 ± 3 vs 50 ± 20,p = 0.003), LVOs (16.5 ± 3.8 vs 8.3 ± 5.9,p = 0.008), and IV-tPA (10.9 ± 3.4 vs 5.3 ± 2.9,p = 0.0047), whereas the mean weekly proportion of LVOs (18 % ±5 vs 16 % ±7,p = 0.24) and IV-tPA (10.4 % ±4.5 vs. 9.9 % ±2.4,p = 0.66) remained the same, when compared to the seasonal pre-COVID-19 period. Additionally, an increased proportion of patients presented with a severe disease (NIHSS > 14) during the COVID-19 period (29.7 % vs 24.5 %,p < 0.025). The odds of being discharged to home were 26 % greater in the COVID-19 period when compared to seasonal pre-COVID-19 period (OR:1.26, 95 % CI:1.07-1.49,p = 0.016).

CONCLUSIONS

During COVID-19 period there was a decrease in volume of newly diagnosed ischemic stroke cases and IV-tPA administration. Patients admitted to the hospital had severe neurological clinical presentation and were more likely to discharge home.

Ischaemic stroke in the time of coronavirus disease 2019

BACKGROUND AND PURPOSE

Stroke assistance is facing changes and new challenges since COVID-19 became pandemic. A variation on the patient influx might be one of the greater concerns, due to fewer people coming to emergency departments or coming too late. However, no data quantifying this have been published until now. The aim was to analyse the impact of the COVID-19 epidemic outbreak on hospital stroke admissions and their characteristics in our region.

METHODS

The data of every patient admitted to any hospital of our healthcare system with a diagnosis of ischaemic stroke between 30 December 2019 and 19 April 2020 were reviewed. Demographic and clinical data were recorded and compared between periods before and after the setting of the state of emergency secondary to the COVID-19 outbreak.

RESULTS

In total, 354 patients with ischaemic stroke were admitted in our study period. There was a weekly average of 27.5 cases before the setting of the state of emergency against 12 afterwards (P < 0.001). This drop in stroke cases occurred progressively from week 11, persisting in time despite the decrease in confirmed cases of COVID-19. No differences in the proportion of intravenous thrombolysis (21.1% vs. 21.5%, P = 0.935) or endovascular therapy (12.4% vs. 15.2%, P = 0.510) were found, nor in other demographic or clinical characteristics except for median onset-to-door time (102 vs. 183 min, P = 0.015).

CONCLUSIONS

This observational study offers the perspective of a whole region in one of the countries more heavily stricken by the SARS-CoV-2 epidemic and shows that the decrease of stroke events, since the beginning of the COVID-19 outbreak, happened globally and without any specific patient distribution.

Seasonal variations in cause-specific mortality and transition to renal replacement therapy among patients with end-stage renal disease

Despite some studies showing seasonal variations in mortality and the transition to renal replacement therapy in patients with end-stage renal disease, detailed evidence is still scarce. We investigated seasonal variations in patients with end-stage renal disease using a large Japanese database for dialysis patients. We compared the fractions of all-cause and cause-specific mortality and the transition to renal replacement therapy among seasons and performed a mixed-effects Poisson regression analysis to compare the mortality among seasons after adjustment for some variables. The initiation of hemodialysis was highest in winter and lowest in summer. Seasonality in the initiation of peritoneal dialysis and transition to kidney transplantation differed from hemodialysis. All-cause mortality was highest in the winter and lowest in the summer. Death from coronary artery disease, heart failure, cerebral hemorrhage, and infectious pneumonia had similar seasonality, but death from cerebral infarction, septicemia, or malignant tumor did not have similar seasonality. In conclusion, the initiation of hemodialysis, all-cause mortality, and mortality from coronary heart disease, heart failure, cerebral hemorrhage, and infectious pneumonia were significantly highest in winter and lowest in summer. However, the initiation of peritoneal dialysis, transition to kidney transplantation, or mortality from cerebral infarction, septicemia, or malignant tumor did not have similar seasonal variations.