Effects of meteorological factors on the onset of subarachnoid hemorrhage: a time-series analysis

Epidemiology of Subarachnoid Hemorrhage in Isolated Islands in Japan: A Population-based Study in the Miyako Islands

The Miyako Islands (with a population of approximately 50,000) are located in southwestern Japan, with a subtropical oceanic climate. This isolated location permitted a retrospective population-based epidemiological study of subarachnoid hemorrhage. We retrospectively enrolled 110 consecutive patients from 2010 to 2019 using the subarachnoid hemorrhage database at Okinawa Miyako Hospital, which is the only local facility with neurosurgeons. We calculated the incidence of subarachnoid hemorrhage standardized to the entire Japanese population. The seasonal distribution of subarachnoid hemorrhage onset and patients' epidemiological characteristics were also investigated. The standardized annual incidence of subarachnoid hemorrhage was 21.4 per 100,000 population, as reported previously in Japan. The patients' mean age was 62.1 ± 15.4 years, and women constituted 60.9%. Anterior communicating artery aneurysms were most common. The endovascular treatment for ruptured aneurysms was increasing as standard levels in Japan. The rates of symptomatic vasospasm and secondary hydrocephalus requiring additional neurosurgical treatment were 2.7% and 19.1%, respectively. The mortality rate was 23.6%. The percentage of patients with a modified Rankin scale score of 0-2 at discharge was 55.5%. There were no differences in the frequency of subarachnoid hemorrhage associated with seasonal distribution or climatic factors. The incidence, baseline characteristics, and clinical outcomes of subarachnoid hemorrhage in the Miyako Islands were similar to those in other regions of Japan. There are preferable epidemiological backgrounds for further practical clinical research.

Relationship of Ambient Temperature Parameters to Stroke Incidence in a Japanese Population - Takashima Stroke Registry, Japan, 1988-2010

BACKGROUND

Using a population-based stroke registry system, we evaluated the relationship between ambient temperature parameters and stroke incidence in a Japanese population.Methods and Results:We analyzed data from the Takashima Stroke Registry, which records all stroke occurrences in Takashima City, Japan. The study period of 8,401 days was divided into quintiles of daily weather parameters, and the middle quintile was used as the reference category. Incidence rates (IR per 100,000 person-years) were calculated across the quintiles. Poisson regression analysis was used to calculate the effect of temperature parameters on stroke incidence. There were 2,405 first-ever strokes (1,294 men), including 1,625 ischemic, 545 cerebral hemorrhages, 213 subarachnoid hemorrhages, and 22 unclassified strokes. The stroke IR was higher in the middle quintile of average temperature, 357.3 (328.4-388.8), and for other parameters. After adjustment for age and sex, for all stroke, the incidence rate ratio (IRR) in the highest (Q5: IRR 0.81, 95% confidence interval (CI) 0.71-0.92) and the second-highest (Q4: IRR 0.80, 95% CI 0.71-0.91) quintile was lower than that in the middle quintile (Q3: Reference). Analogous results were observed for the minimum, maximum, and lag-days temperatures, also in the subtypes and across ≥65 years of age, also in females.

CONCLUSIONS

Higher temperatures, irrespective of the parameter (average, minimum, or maximum), had a protective effect against stroke occurrence in Japan.

The Subarachnoid Hemorrhage-Weather Myth: A Long-Term Big Data and Deep Learning Analysis

Objective: The frequency of aneurysmal subarachnoid hemorrhage (aSAH) presents complex fluctuations that have been attributed to weather and climate changes in the past. In the present long-term big data and deep learning analysis, we have addressed this long-held myth.

Methods: Bleeding dates and basic demographic data for all consecutive patients (n = 1,271) admitted to our vascular center for treatment of aSAH between January 2003 and May 2020 (6,334 days) were collected from our continuously maintained database. The meteorological data of the local weather station, including 13 different weather and climate parameters, were retrieved from Germany's National Meteorological Service for the same period. Six different deep learning models were programmed using the Keras framework and were trained for aSAH event prediction with meteorological data from January 2003 to June 2017, with 10% of this dataset applied for data validation and model improvement. The dataset from July 2017 to May 2020 was tested for aSAH event prediction accuracy for all six models using the area under the receiver operating characteristic curve (AUROC) as the metric.

Results: The study group comprised of 422 (33.2%) male and 849 (66.8%) female patients with an average age of 55 ± 14 years. None of the models showed an AUROC larger than 60.2. From the presented data, the influence of weather and climate on the occurrence of aSAH events is extremely unlikely.

Conclusion: The myth of special weather conditions influencing the frequency of aSAH is disenchanted by this long-term big data and deep learning analysis.

Association between stroke occurrence and changes in atmospheric circulation

Background

The impact of weather on morbidity from stroke has been analysed in previous studies. As the risk of stroke was mostly associated with changing weather, the changes in the daily stroke occurrence may be associated with changes in atmospheric circulation. The aim of our study was to detect and evaluate the association between daily numbers of ischaemic strokes (ISs) and haemorrhagic strokes (HSs) and the teleconnection pattern.

Methods

The study was performed in Kaunas, Lithuania, from 2000 to 2010. The daily numbers of ISs, subarachnoid haemorrhages (SAHs), and intracerebral haemorrhages (ICHs) were obtained from the Kaunas Stroke Register. We evaluated the association between these types of stroke and the teleconnection pattern by applying Poisson regression and adjusting for the linear trend, month, and other weather variables.

Results

During the study period, we analysed 4038 cases (2226 men and 1812 women) of stroke. Of these, 3245 (80.4%) cases were ISs, 533 (13.2%) cases were ICHs, and 260 (6.4%) cases were SAHs. An increased risk of SAH was associated with a change in mean daily atmospheric pressure over 3.9 hPa (RR = 1.49, 95% CI 1.14–1.96), and a stronger El Niño event had a protective effect against SAHs (RR = 0.34, 95% CI 0.16–0.69). The risk of HS was positively associated with East Atlantic/West Russia indices (RR = 1.13, 95% CI 1.04–1.23). The risk of IS was negatively associated with the Arctic Oscillation index on the same day and on the previous day (RR = 0.97, p < 0.033). During November–March, the risk of HS was associated with a positive North Atlantic Oscillation (NAO) (RR = 1.29, 95% CI 1.03–1.62), and the risk of IS was negatively associated with the NAO index (RR = 0.92, 95% CI 0.85–0.99).

Conclusions

The results of our study provide new evidence that the North Atlantic Oscillation, Arctic Oscillation, East Atlantic/West Russia, and El Niño-Southern Oscillation pattern may affect the risk of stroke. The impact of these teleconnections is not identical for various types of stroke. Emergency services should be aware that specific weather conditions are more likely to prompt calls for more severe strokes.

Meteorological factors for subarachnoid hemorrhage in the greater Düsseldorf area revisited: a machine learning approach to predict the probability of admission of patients with subarachnoid hemorrhage

BACKGROUND

Reported data regarding the relation between the incidence of spontaneous subarachnoid hemorrhage (SAH) and weather conditions are conflicting and do so far not allow prognostic models.

METHODS

Admissions for spontaneous SAH (ICD I60.*) 2009-2018 were retrieved form our hospital data base. Historical meteorological data for the nearest meteorological station, Düsseldorf Airport, was retrieved from the archive of the Deutsche Wetterdienst (DWD). Airport is in the center of our catchment area with a diameter of approximately 100 km. Pearson correlation matrix between mean daily meteorological variables and the daily admissions of one or more patients with subarachnoid hemorrhage was calculated and further analysis was done using deep learning algorithms.

RESULTS

For the 10-year period from January 1, 2009 until December 31, 2018, a total of 1569 patients with SAH were admitted. No SAH was admitted on 2400 days (65.7%), 1 SAH on 979 days (26.7%), 2 cases on 233 days (6.4%), 3 SAH on 37 days (1.0%), 4 in 2 days (0.05%), and 5 cases on 1 day (0.03%). Pearson correlation matrix suggested a weak positive correlation of admissions for SAH with precipitation on the previous day and weak inverse relations with the actual mean daily temperature and the temperature change from the previous days, and weak inverse correlations with barometric pressure on the index day and the day before. Clustering with admission of multiple SAH on a given day followed a Poisson distribution and was therefore coincidental. The deep learning algorithms achieved an area under curve (AUC) score of approximately 52%. The small difference from 50% appears to reflect the size of the meteorological impact.

CONCLUSION

Although in our data set a weak correlation of the probability to admit one or more cases of SAH with meteorological conditions was present during the analyzed time period, no helpful prognostic model could be deduced with current state machine learning methods. The meteorological influence on the admission of SAH appeared to be in the range of only a few percent compared with random or unknown factors.

Role of bioclimate conditions on cerebral aneurysm rupture in the Brittany region of France

INTRODUCTION

Subarachnoid hemorrhage (SAH) from intracranial aneurysm rupture is an unpredictable event responsible for significant morbidity and mortality. Despite inconsistencies, some studies suggest a potential role of climate conditions in SAH onset. The purpose of this study was to determine the impact of climatic and lunar factors on onset of SAH in an oceanic climate such as that of Brittany, France.

METHODS

All adults with SAH admitted to the neurosurgery department and intensive care unit of the University Hospital of Rennes (France) between January 1st, 2011 and December 31st, 2012 were included. Meteorological variables, their variations, lunar phases and tidal coefficients were compared between days with and without SAH.

RESULTS

We retrospectively included 295 patients with SAH. Mean minimum temperature was significantly lower during days with SAH (7.7±4.7°C versus 8.3±4.6°C; P=0.039); temperature variation between 2 successive days was significantly greater for days with SAH (8.6±4.1°C versus 7.9±3.8°C; P<0.01). Multivariate analysis showed that a 2-day temperature drop greater than or equal to 8°C was associated with 35% increased risk of SAH (odds ratio 1.35 [1.03-1.77]). There were no significant effects of other meteorological variables, lunar phase or tidal coefficient on SAH occurrence.

CONCLUSION

Low temperature and sudden temperature drop were associated with increased occurrence of SAH in Brittany, France.

Association Between Meteorological Factors and the Rupture of Intracranial Aneurysms

Background Both meteorological factors and morphological factors are important factors to predict intracranial aneurysm rupture. This study investigated the relationship between meteorological factors and aneurysmal subarachnoid hemorrhage (aSAH). Additionally, the morphological differences between ruptured and unruptured aneurysms under these high-risk meteorological conditions were assessed. Methods and Results The records of 1751 patients with aSAH with 2124 intracranial aneurysms were retrospectively analyzed. Spearman rank correlation analysis was used to assess the risks of incident aSAH on the basis of daily meteorological data. Morphological parameters were analyzed using 1-way ANOVA tests, and significant parameters (P<0.05) were further examined using a multivariable logistic regression analysis. Daily aSAH incidence had significant negative correlations with daily mean, maximum, and minimum temperature (P<0.001) and a significant positive correlation with daily mean atmospheric pressure (P<0.001). Additionally, 58 patients with multiple aneurysms were assessed to determine morphological differences. There were significant differences in the mean values for aneurysm size, neck width, length, height, width, parent artery diameter, shape of the aneurysm, aspect ratio, size ratio, and bottleneck factor (P<0.05). The multivariable logistic regression analysis showed that aspect ratio (β=1.277, odds ratio=3.585, 95% CI, 1.588-8.090; P=0.002) was an independent risk factor for aneurysm rupture. Receiver operating characteristic curve analysis indicated that the ruptured aneurysm threshold of size was 3.45 mm and aspect ratio was 1.05. Conclusions Lower daily mean, maximum, and minimum temperatures and a higher daily mean atmospheric pressure were associated with an increased rate of aSAH. Additionally, under these meteorological conditions, the aneurysm size and aspect ratio thresholds for predicting rupture of an aneurysm may be lower.

Meteorological Variation Is a Predisposing Factor for Aneurismal Subarachnoid Hemorrhage: A 5-Year Multicenter Study in Fuzhou, China

OBJECTIVE

The climatic characteristics of aneurysmal subarachnoid hemorrhage (aSAH) have been reported, but consensus has not yet been reached. It is of great significance to elucidate the relationships between meteorological variation and aSAH in regions with specific climate patterns. We analyzed the occurrence of aSAH in the capital city of Fujian Province, China, through a multicenter, 5-year study, and aimed to reveal the meteorological influences on aSAH in the coastal city of eastern Fujian under the subtropical marine monsoon condition.

METHODS

A total of 2555 consecutive patients with aSAH in Fuzhou were collected using specialized stroke admission database from January 2013 to December 2017. Meteorological parameters including temperature, atmospheric pressure, and humidity were obtained from China Surface Meteorological Station during the same period. Poisson regression was used to explore the association between meteorological parameters and aSAH to calculate the incidence rate ratios (IRRs) with corresponding 95% confidence intervals (CIs). Generalized additive model analysis further revealed the nonlinear relationships between weather and aSAH.

RESULTS

Daily minimum temperature (IRR 0.976, 95% CI 0.958-0.996) and maximum pressure (IRR 1.022, 95% CI 1.001-1.042) were independently correlated with the onset of aSAH. Low temperature (below 16°C) and excessive atmospheric pressure (above 1008 hPa) increased the risk of aSAH. In addition, March in spring and December in winter were the 2 ictus peaks in Fuzhou throughout the year.

CONCLUSIONS

Cold and excessive atmospheric pressure are triggers for the occurrence of aSAH; March in spring and December in winter are the predominant onset periods in Fuzhou.

Impact of temperature decline from the previous day as a trigger of spontaneous subarachnoid hemorrhage: case-crossover study of prefectural stroke database

OBJECTIVE

Several environmental factors have been reported to correlate with incidence of spontaneous subarachnoid hemorrhage (SAH). However, because of different patient selection and study designs among these studies, meteorological factors that trigger the incidence of SAH in a short hazard period remain unknown. Among meteorological factors, daily temperature changes may disrupt and violate homeostasis and predispose to cerebrovascular circulatory disturbances and strokes. The authors aimed to investigate whether a decline in the temperature from the highest of the previous day to the lowest of the event day (temperature decline from the previous day [TDP]) triggers SAH in the prefecture-wide stroke database.

METHODS

All 28 participating institutions with primary or comprehensive stroke centers located throughout Kochi Prefecture, Japan, were included in the study. Data collected between January 2012 and December 2016 were analyzed, and 715 consecutive SAH patients with a defined date of onset were enrolled. Meteorological data in this period were obtained from the Kochi Local Meteorological Observatory. A case-crossover study was performed to investigate association of TDP and other environmental factors with onset of SAH.

RESULTS

The increasing TDP in 1°C on the day of the SAH event was associated with an increased incidence of SAH (OR 1.041, 95% CI 1.007-1.077) after adjustment for other environmental factors. According to the stratified analysis, a significant association between TDP and SAH was observed in women, patients < 65 years old, and patients with weekday onset. Among these factors, increasing TDP had a great impact on SAH onset in patients < 65 years old (p = 0.028, Mann-Whitney U-test).

CONCLUSIONS

TDP, temperature decline from the highest of the previous day to the lowest of the day, was correlated with the incidence of spontaneous SAH, particularly in younger patients < 65 years old.

Mean air temperature as a risk factor for stroke mortality in São Paulo, Brazil

In Brazil, chronic diseases account for the largest percentage of all deaths among men and women. Among the cardiovascular diseases, stroke is the leading cause of death, accounting for 10% of all deaths. We evaluated associations between stroke and mean air temperature using recorded mortality data and meteorological station data from 2002 to 2011. A time series analysis was applied to 55,633 mortality cases. Ischemic and hemorrhagic strokes (IS and HS, respectively) were divided to test different impact on which subgroup. Poisson regression with distributed lag non-linear model was used and adjusted for seasonality, pollutants, humidity, and days of the week. HS mortality was associated with low mean temperatures for men relative risk (RR) = 2.43 (95% CI, 1.12-5.28) and women RR = 1.39 (95% CI, 1.03-1.86). RR of IS mortality was not significant using a 21-day lag window. Analyzing the lag response separately, we observed that the effect of temperature is acute in stroke mortality (higher risk among lags 0-5). However, for IS, higher mean temperatures were significant for this subtype with more than 15-day lag. Our findings showed that mean air temperature is associated with stroke mortality in the city of São Paulo for men and women and IS and HS may have different triggers. Further studies are needed to evaluate physiologic differences between these two subtypes of stroke.

Atmospheric Pressure Variation is a Delayed Trigger for Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

There is an ongoing search for conditions that induce spontaneous subarachnoid hemorrhage (SAH). The seasonal pattern of SAH is shown in a large meta-analysis of the literature, but its explanation remains undecided. There is a clear need for sound meteorologic data to further elucidate the seasonal influence on SAH. Because of the stable and densely monitored atmospheric situation in the north of the Netherlands, we reviewed our unique cohort on the seasonal incidence of SAH and the association between SAH and local atmospheric changes.

METHODS

Our observational cohort study included 1535 patients with spontaneous SAH admitted to our neurovascular center in the north of the Netherlands between 2000 and 2015. Meteorologic data could be linked to the day of the ictus. To compare SAH incidences over the year and to test the association with meteorologic conditions, incidence rate ratios (IRRs) with corresponding 95% confidence intervals (CIs) were used, calculated by Poisson regression analyses.

RESULTS

Atmospheric pressure variations were significantly associated with aneurysmal SAH. In particular, the pressure change on the second and third day before the ictus was independently correlated to a higher incidence of aneurysmal SAH (IRR, 1.11; 95% CI, 1.00-1.23). The IRR for aneurysmal SAH in July was calculated 0.67 (95% CI, 0.49-0.92) after adjustment for temperature and atmospheric pressure changes.

CONCLUSIONS

Atmospheric pressure variations are a delayed trigger for aneurysmal SAH. Also, a significantly decreased incidence of aneurysmal SAH was noted in July.

Monthly variations in aneurysmal subarachnoid hemorrhage incidence and mortality: Correlation with weather and pollution

BACKGROUND AND PURPOSE

Although the effect of weather and air pollution on the occurrence of subarachnoid hemorrhage (SAH) has been investigated, results have remained inconsistent. The present study aimed to determine the seasonality of aneurysmal subarachnoid hemorrhage occurrence and mortality.

METHODS

We used the National Inpatient Sample database to evaluate the effect of meteorological factors and air pollutants on patients with subarachnoid hemorrhage in Korea between 2011 and 2014. Monthly variations in SAH occurrence and mortality were analyzed using locally weighted scatter plot smoothing curves. Multivariate Poisson generalized linear regression models were used to evaluate potential independent meteorological and pollutant variables associated with SAH occurrence and mortality.

RESULTS

In total, 21,407 patients who underwent clip or coil treatment owing to aneurysmal SAH in Korea from January 1, 2011, to December 31, 2014, were included. The crude incidence rate of SAH in Korea was 10.5 per 100,000 people per year. An approximately 0.5% lower risk of SAH was observed per 1°C increase in mean monthly temperature (relative risk, 0.995; 95% confidence interval [CI], 0.992-0.997; p < 0.001), while an approximately 2.3% higher risk of SAH was observed per 1°C increase in mean monthly diurnal temperature.

CONCLUSIONS

We showed distinct patterns of seasonal and monthly variation in the occurrence and mortality of SAH. Our findings suggest that meteorological factors may play an important role in monthly variations in the occurrence of aneurysmal SAH.

The association between lunar phase and intracranial aneurysm rupture: Myth or reality? Own data and systematic review

Background

It is a common belief in medical community that lunar phases have an impact on human health. A growing body of evidence indicates that lunar phases can predict the risk to develop acute neurological and vascular disorders. The goal of present report was to present our institution data and to perform systematic review of studies examining the association of intracranial aneurysm rupture with moon phases.

Methods

We identified all patients admitted to our department for ruptured intracranial aneurysms in a period between November, 2011 and December, 2014. Patients with a known aneurysm rupture date were included. Lunar phases were determined by dividing lunar month (29.5 days) into eight equal parts, i.e., new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter and waning crescent. A systematic literature review was undertaken to identify studies that evaluated the association of lunar phases with the incident of intracranial aneurysm rupture.

Result

One hundred and eighty-six patients (62 men and 124 women, median age 56 years) were admitted to our department for treatment of ruptured intracranial aneurysms. The rate of intracranial aneurysm rupture was equally distributed across all phases of the lunar cycle (X² [7; 185] = 12.280, p = 0.092). We identified three studies that evaluated the association between incident intracranial aneurysm rupture and lunar phases with a total of 1483 patients. One study from Lebanon found that the incidence rate of intracranial aneurysm rupture was statistically significantly greater during the new moon phase (25% cases), relative to the other seven lunar phases (p < 0.001). Two subsequent studies from Austria and Germany in larger patient samples (n = 717 and n = 655, respectively) did not find an association between lunar phases and intracranial aneurysm rupture (p-values of 0.84 and 0.97, respectively). When analyzing all four studies together, we did not find an association between lunar phases and incidence of intracranial aneurysm rupture (X² [1668; 7] = 2.080, p = 0.955).

Conclusions

Moon phases are not associated with incidence of intracranial aneurysm rupture. Studies investigating the association of intracranial aneurysm rupture with lunar illumination defined using more sensitive approaches are encouraged.

Associations between Temperature and Hospital Admissions for Subarachnoid Hemorrhage in Korea

The relationship between temperature and subarachnoid hemorrhage (SAH) is less studied than that between temperature and myocardial infarction or other cardiovascular diseases. This study investigated the association between daily temperature and risk of SAH by analyzing the hospital admission records of 111,316 SAH patients from 2004 to 2012 in Korea. A Poisson regression model was used to examine the association between temperature and daily SAH hospital admissions. To analyze data and identify vulnerable groups, we used the following subgroups: sex, age, insurance type, area (rural or urban), and different climate zones. We confirmed a markedly higher SAH risk only for people of low socioeconomic status in both hot and cold temperatures; the relative risk (RR) in the Medicaid group was significantly increased and ranged from 1.04 to 1.11 for cold temperatures and 1.10 to 1.11 for hot temperatures. For the National Health Insurance group, the RR was increased to 1.02 for the maximum temperature only. The increased risk for SAH was highest in the temperate zone. An increase above the heat threshold temperature and a decrease below the cold threshold temperature were correlated with an increased risk of SAH in susceptible populations and were associated with different lag effects and RRs.

Relationship of meteorological factors and acute stroke events in Kaunas (Lithuania) in 2000-2010

Some researchers have hypothesised that meteorological factors may have an impact on acute cerebrovascular diseases. The aim of this study was to determine an impact of some meteorological factors on occurrence of acute cerebrovascular events in the middle-aged Kaunas population. Kaunas stroke register data were used. Data on meteorological factors for the time period from 2000 to 2010 were obtained from the Lithuanian Hydrometeorological Service Kaunas Meteorological Station. We analysed 4038 cases with stroke. Ischemic strokes composed 80.4% and haemorrhagic strokes-19.6%. According to Poisson regression analysis, significant negative correlation between ischemic, haemorrhagic and all types of stroke and ambient air temperature was found (β coefficient - 0.007, -0.016, -0.009, p < 0.001, respectively). Results of ARIMA showed that ambient temperature of the day of stroke onset was associated with the occurrence of ischemic, haemorrhagic and all types of stroke: when temperature was lower, the risk of stroke was higher (-0.006, -0.003, -0.009, p < 0.001, respectively). Low temperature on the event day and 1 and 2 days before the event was associated with higher incidence of haemorrhagic stroke in women. Low ambient temperature on the event day increased incidence of haemorrhagic stroke in subjects 55-64 years. High wind speed on the event day was associated with higher incidence of ischemic stroke in older subjects. Meteorological factors may have some impact on the risk of acute cerebrovascular events. Health care providers should focus on preventive measures, which can reduce these risks.

Ambient Temperature and Stroke Occurrence: A Systematic Review and Meta-Analysis

Biologically plausible associations exist between climatic conditions and stroke risk, but study results are inconsistent. We aimed to summarize current evidence on ambient temperature and overall stroke occurrence, and by age, sex, and variation of temperature. We performed a systematic literature search across MEDLINE, Embase, PsycINFO, CINAHL, Web of Science, and GEOBASE, from inception to 16 October 2015 to identify all population-based observational studies. Where possible, data were pooled for meta-analysis with Odds ratios (OR) and corresponding 95% confidence intervals (CI) by means of the random effects meta-analysis. We included 21 studies with a total of 476,511 patients. The data were varied as indicated by significant heterogeneity across studies for both ischemic stroke (IS) and intracerebral hemorrhage (ICH). Pooled OR (95% CI) in every 1 degree Celsius increase in ambient temperature was significant for ICH 0.97 (0.94–1.00), but not for IS 1.00 (0.99–1.01) and subarachnoid hemorrhage (SAH) 1.00 (0.98–1.01). Meta-analysis was not possible for the pre-specified subgroup analyses by age, sex, and variation of temperature. Change in temperature over the previous 24 h appeared to be more important than absolute temperature in relation to the risk of stroke, especially in relation to the risk of ICH. Older age appeared to increase vulnerability to low temperature for both IS and ICH. To conclude, this review shows that lower mean ambient temperature is significantly associated with the risk of ICH, but not with IS and SAH. Larger temperature changes were associated with higher stroke rates in the elderly.

Air Pressure, Humidity and Stroke Occurrence: A Systematic Review and Meta-Analysis

Background/Aims: An influence of climate upon stroke risk is biologically plausible and supported by epidemiological evidence. We aimed to determine whether air pressure (AP) and humidity are associated with hospital stroke admission. Methods: We searched MEDLINE, Embase, PsycINFO, CINAHL, Web of Science, and GEOBASE, from inception to 16 October 2015 to identify relevant population-based observational studies. Where possible, data were pooled for meta-analysis with odds ratios (OR) and corresponding 95% confidence intervals (CI) by means of the random-effect method. Results: We included 11 studies with a total of 314,385 patients. The effect of AP was varied across studies for ischemic stroke (IS) and subarachnoid haemorrhage (SAH). Pooled ORs (95%CI) associated with 1 hPa increase in AP for the risk of IS, intracerebral hemorrhage (ICH) and SAH were 1.00 (0.99–1.01), 1.01 (0.99–1.02) and 1.02 (0.97–1.07) respectively. The pooled ORs (95%CI) associated with 1 percent increase in humidity for the risk of IS and ICH were 1.00 (1.00–1.01) and 1.00 (0.99–1.01) respectively. Conclusion: This review shows that there is no evidence of a relationship between AP or humidity and the occurrence of hospital admission for stroke. Further research is needed to clarify the extent and nature of any relationship between AP, humidity and stroke in different geographical areas.

Association between hemorrhagic stroke occurrence and meteorological factors and pollutants

Background

The purpose of this study is to determine whether intracerebral hemorrhage and subarachnoid hemorrhage have different incidence patterns based on monthly variations in meteorological and air pollution parameters in the Seongdong district of Seoul, South Korea.

Methods

From January 1, 2004 to December 31, 2014, 1,477 consecutive hemorrhagic stroke events (>19 years old) were registered among residents of the Seongdong district, Seoul, South Korea. The authors calculated the relative risk of hemorrhagic stroke and its subtype incidence based on meteorological and air pollution factors. We also estimated relative risk with 95 % confidence intervals using a multivariate Poisson regression model to identify potential independent variables among meteorological factors and pollutants associated with either intracerebral hemorrhage or subarachnoid hemorrhage occurrence.

Results

We observed a negative correlation between intracerebral hemorrhage and mean temperature. In the multivariate Poisson model, particulate matter with an aerodynamic diameter < 10 μm showed positive correlations with intracerebral hemorrhage (relative risk, 1.09; 95 % confidence interval, 1.02 to 1.15; P = 0.012). In contrast, ozone correlated significantly with subarachnoid hemorrhage occurrence (relative risk, 1.32; 95 % confidence interval, 1.10 to 1.58; P = 0.003).

Conclusions

Our findings show the relationship between hemorrhagic stroke and meteorological parameters and pollutants under similar weather and environmental conditions in a small area. Among meteorological and pollutant variables, only higher particulate matter concentrations correlated independently with intracerebral hemorrhage occurrence, while only ozone was independently associated with subarachnoid hemorrhage occurrence. These findings suggest the possibility that there are pathogenic associations between hemorrhagic stroke and meteorological factors and pollutants.

Elevated relative risk of aneurysmal subarachnoid hemorrhage with colder weather in the mid-Atlantic region

We have previously reported an increase of 0.6% in the relative risk of aneurysmal subarachnoid hemorrhage (aSAH) in response to every 1°F decrease in the maximum daily temperature (Tmax) in colder seasons from patients presenting to our regional tertiary care center. We hypothesized that this relationship would also be observed in the warmer summer months with ambient temperatures greater than 70°F. From prospectively collected incidence data for aSAH patients, we investigated absolute Tmax, average daily temperatures, intraday temperature ranges, and the variation of daily Tmax relative to 70°F to assess associations with aSAH incidence for patients admitted to our institution between 1991 and 2009 during the hottest months and days on which Tmax>70°F. For all days treated as a group, the mean Tmax (± standard deviation) was lower when aSAH occurred than when it did not (64.4±18.2°F versus 65.8±18.3°F; p=0.016). During summer months, the odds ratio (OR) of aSAH incidence increased with lower mean Tmax (OR 1.019; 95% confidence interval 1.001-1.037; p=0.043). The proportion of days with aSAH admissions was lower on hotter days than the proportion of days with no aSAH (96% versus 98%; p=0.006). aSAH were more likely to occur during the summer and on days with a temperature fluctuation less than 10°F (8% versus 4%; p=0.002). During the hottest months of the year in the mid-Atlantic region, colder maximum daily temperatures, a smaller heat burden above 70°F, and smaller intraday temperature fluctuations are associated with increased aSAH admissions in a similar manner to colder months. These findings support the hypothesis that aSAH incidence is more likely with drops in temperature, even in the warmer months.

Meteorological Variables Associated with Stroke

To elucidate relationships between meteorological variables and incidence of stroke, we studied patients diagnosed with stroke after presenting to the emergency department (May 1, 2010–August 8, 2011). Patient demographics and medical data were reviewed retrospectively with regional meteorological data. Across 467 days, 134 stroke events were recorded on 114 days. On stroke days, maximum temperature (max T) and atmospheric pressure (AP) combined were a significant predictor of stroke (max T odds ratio (OR) = 1.014, 95% confidence interval (CI) = 1.003–1.026, and P = 0.04; AP: OR = 1.033, 95% CI = 0.997–1.071, and P = 0.02). When the patient could identify the hour of the stroke, average temperature (avg T) was significantly higher than nonstroke hours (18.2°C versus 16.16°C, P = 0.04). Daily fluctuations in AP and avg T also had significant effects on stroke incidence (AP: OR = 0.629, 95% CI = 0.512–0.773, and P = 0.0001; avg T OR = 1.1399, 95% CI = 1.218–606, and P = 0.0001). Patient age, stroke history, body mass index, ethnicity, and sex were further contributors to stroke risk. Temperature, atmospheric pressure, and certain physiological conditions likely play roles in weather-related stroke susceptibility. The mechanisms driving these associations are not fully understood.

The association between meteorological parameters and aneurysmal subarachnoid hemorrhage: a nationwide analysis

Prior research has suggested that regional weather patterns impact the risk of rupture of cerebral aneurysms, but the findings in the literature have been inconsistent. Furthermore, no nationwide analysis to date has examined the association between meteorological factors and the post-procedural outcomes of patients after the treatment for ruptured cerebral aneurysms. The purpose of this study was to use a nationwide sample to analyze the association between specific meteorological parameters—temperature, precipitation, sunlight, and humidity—and hospital admission rate for and outcome after aneurysmal subarachnoid hemorrhage. Patients were identified using the Nationwide Inpatient Sample (2001–2010): Those with an ICD-9 diagnosis code for subarachnoid hemorrhage and a procedural code for aneurysm repair were included. Climate data were obtained from the State of the Climate Report 2010 released by the National Climatic Data Center. Multivariate regression models were constructed to analyze the association between average state monthly temperature, precipitation, and percent possible sunlight, as well as relative morning humidity and both monthly hospital admission rate, adjusted for annual state population in millions, and in-hospital mortality. 16,970 admissions were included from 723 hospitals across 41 states. Decreased daily sunlight and lower relative humidity were associated with an increased rate of admission for ruptured cerebral aneurysms (p<0.001), but had no association with differential inpatient mortality. No significant changes in these observed associations were seen when multivariate analyses were constructed. This is the first nationwide study to suggest that decreased sunlight and lower relative humidity are associated with admission for ruptured cerebral aneurysms. While it has been postulated that external atmospheric factors may cause hormonal and homeostatic changes that impact the risk of rupture of cerebral aneurysms, additional research is needed to confirm and further understand these relationships.

Aneurysmal subarachnoid hemorrhage: relationship to solar activity in the United States, 1988-2010

Aneurysmal subarachnoid hemorrhage (SAH) is a common condition treated by neurosurgeons. The inherent variability in the incidence and presentation of ruptured cerebral aneurysms has been investigated in association with seasonality, circadian rhythm, lunar cycle, and climate factors. We aimed to identify an association between solar activity (solar flux and sunspots) and the incidence of aneurysmal SAH, all of which appear to behave in periodic fashions over long time periods. The Nationwide Inpatient Sample (NIS) provided longitudinal, retrospective data on patients hospitalized with SAH in the United States, from 1988 to 2010, who underwent aneurysmal clipping or coiling. Solar activity and SAH incidence data were modeled with the cosinor methodology and a 10-year periodic cycle length. The NIS database contained 32,281 matching hospitalizations from 1988 to 2010. The acrophase (time point in the cycle of highest amplitude) for solar flux and for sunspots were coincident. The acrophase for aneurysmal SAH incidence was out of phase with solar activity determined by non-overlapping 95% confidence intervals (CIs). Aneurysmal SAH incidence peaks appear to be delayed behind solar activity peaks by 64 months (95% CI; 56-73 months) when using a modeled 10-year periodic cycle. Solar activity (solar flux and sunspots) appears to be associated with the incidence of aneurysmal SAH. As solar activity reaches a relative maximum, the incidence of aneurysmal SAH reaches a relative minimum. These observations may help identify future trends in aneurysmal SAH on a population basis.

The influence of meteorological and geomagnetic factors on acute myocardial infarction and brain stroke in Moscow, Russia

Evidence of the impact of air temperature and pressure on cardiovascular morbidity is still quite limited and controversial, and even less is known about the potential influence of geomagnetic activity. The objective of this study was to assess impacts of air temperature, barometric pressure and geomagnetic activity on hospitalizations with myocardial infarctions and brain strokes. We studied 2,833 myocardial infarctions and 1,096 brain strokes registered in two Moscow hospitals between 1992 and 2005. Daily event rates were linked with meteorological and geomagnetic conditions, using generalized linear model with controls for day of the week, seasonal and long-term trends. The number of myocardial infarctions decreased with temperature, displayed a U-shaped relationship with pressure and variations in pressure, and increased with geomagnetic activity. The number of strokes increased with temperature, daily temperature range and geomagnetic activity. Detrimental effects on strokes of low pressure and falling pressure were observed. Relative risks of infarctions and strokes during geomagnetic storms were 1.29 (95% CI 1.19-1.40) and 1.25 (1.10-1.42), respectively. The number of strokes doubled during cold spells. The influence of barometric pressure on hospitalizations was relatively greater than the influence of geomagnetic activity, and the influence of temperature was greater than the influence of pressure. Brain strokes were more sensitive to inclement weather than myocardial infarctions. This paper provides quantitative estimates of the expected increases in hospital admissions on the worst days and can help to develop preventive health plans for cardiovascular diseases.

[The relationship between aneurysmal subarachnoid hemorrhage and meteorological parameters based on a series of 236 French patients]

Subarachnoid hemorrhage (SAH) is a sudden and potentially severe event with mortality rates ranging between 24 and 30 % depending on the initial clinical condition. Studies have attempted to assess the possible influence of meteorological parameters on the occurrence of SAH. However, this idea remains very controversial and the results vary widely from one study to another. Our study is the second largest French series, and first performed in a homogeneous series of patients. The aim of our study was to attempt to establish a relationship between the weather (i.e.) temperature variations and daily variations of atmospheric pressure in the days before the onset of SAH and the same day and the occurrence of non-traumatic SAH in a homogeneous population of 236 patients from a single center, over a period of 7 years (2002 to 2008). This retrospective study does not suggest any relationship between the occurrence of SAH and meteorological data studied. Moreover, no relationship was observed between mean changes in temperature or pressure and the occurrence of SAH, that the day of the bleeding or the days preceding the SAH. However, a female predominance was observed and a relatively high mortality rate of 18.3 %. The distribution of the occurrence of an SAH was random. As it seems impossible to provide logistics and organization of care for non-traumatic SAH, the care system must remain vigilant throughout the year.

Meteorological influences on the incidence of aneurysmal subarachnoid hemorrhage - a single center study of 511 patients

OBJECTIVE

To assess the potential meteorological influence on the incidence of aneurysmal subarachnoid hemorrhage (SAH). Previous studies used inhomogeneous patient groups, insufficient study periods or inappropriate statistics.

PATIENTS AND METHODS

We analyzed 511 SAH admissions between 2004 and 2012 for which aneurysmal rupture occurred within the Zurich region. The hourly meteorological parameters considered are: surface pressure, 2-m temperature, relative humidity and wind gusts, sunshine, and precipitation. For all parameters we investigate three complementary statistical measures: i) the time evolution from 5 days before to 5 days after the SAH occurrence; ii) the deviation from the 10-year monthly mean; and iii) the change relative to the parameter's value two days before SAH occurrence. The statistical significance of the results is determined using a Monte Carlo simulation combined with a re-sampling technique (1000×).

RESULTS

Regarding the meteorological parameters considered, no statistically significant signal could be found. The distributions of deviations relative to the climatology and of the changes during the two days prior to SAH events agree with the distributions for the randomly chosen days. The analysis was repeated separately for winter and summer to exclude compensating effects between the seasons.

CONCLUSION

By using high-quality meteorological data analyzed with a sophisticated and robust statistical method no clearly identifiable meteorological influence for the SAH events considered can be found. Further studies on the influence of the investigated parameters on SAH incidence seem redundant.

Falling temperature and colder weather are associated with an increased risk of aneurysmal subarachnoid hemorrhage

OBJECTIVE

To use weather data to predict increased incidence of aneurysmal subarachnoid hemorrhage (aSAH) at a large institution with an extensive referral network in response to falling temperatures.

METHODS

In a retrospective study, 1175 prospectively collected aSAH cases accrued over 18 years from one hospital were reviewed to determine if season, maximum ambient temperature (MAT), average relative humidity, and atmospheric pressure were related to incidence of aSAH at that institution on a given day. A Poisson regression model was used to assess daily risk of incident aSAH based on daily MAT and 1-day change in MAT.

RESULTS

A MAT decrease of 1°F from one day to the next was associated with a 0.6% increase in risk of aSAH (relative risk [RR]=1.006, P=0.016). The increased risk associated with MAT decrease from the previous day was especially strong for female patients (RR=1.008/°F, P=0.007) and drove the overall model, representing 72% of cases. In addition, warmer temperatures were associated with a decreased risk of aSAH; each 1°F increase in temperature compared with the previous day was associated with a 0.3% decrease in risk of aSAH (RR=0.997; P<0.001).

CONCLUSIONS

A 1-day decrease in temperature and colder daily temperatures were associated with an increased risk of incident aSAH at a single institution with a large referral network. These variables appeared to act synergistically and independently of season. These relationships were particularly predominant in the fall when the transition from warmer to colder temperatures occurred.

Subarachnoid hemorrhage incidence in the United States does not vary with season or temperature

BACKGROUND AND PURPOSE

Previous studies have suggested seasonal variations in rates of spontaneous rupture of intracranial aneurysms, leading to potentially devastating SAH. In an effort to identify a seasonal effect, variation in SAH incidence and in-hospital mortality rates were examined as they relate to admission month, temperature, and climate using HCUP's Nationwide Inpatient Sample.

MATERIALS AND METHODS

Cases of nontraumatic SAH and subsequent in-hospital mortality were extracted from the 2001-2008 NIS and associated with month of occurrence, local average monthly temperatures, and USDA climate zone. Multivariate regression analysis was used to study how admission month, temperature, and climate affected SAH admission and mortality rates.

RESULTS

Among 57,663,486 hospital admissions from the 2001-2008 NIS, 52,379 cases of spontaneous SAH (ICD-9-CM 430) and 13,272 cases of subsequent in-hospital mortality were identified. SAH incidence and in-hospital mortality rates were not significantly correlated with a monthly/seasonal effect (incidence, χ(2) = 2.94, P = .99; mortality, χ(2) = 6.91, P = .81). However, SAH incidence significantly varied with climate (P < .0001, zones 11 and 7) but not with temperature (P = .1453), whereas average monthly temperature and climate had no significant correlation with in-hospital mortality (temperature, P = .3005; climate, P = .0863).

CONCLUSIONS

We identified no significant monthly or temperature-related effect in the incidence of SAH. Our data suggest that certain climate zones within the United States may be associated with significantly different SAH incidence, but the origins of these differences remain unclear and are probably unrelated to meteorologic variables.

Long-term prediction of emergency department revenue and visitor volume using autoregressive integrated moving average model

This study analyzed meteorological, clinical and economic factors in terms of their effects on monthly ED revenue and visitor volume. Monthly data from January 1, 2005 to September 30, 2009 were analyzed. Spearman correlation and cross-correlation analyses were performed to identify the correlation between each independent variable, ED revenue, and visitor volume. Autoregressive integrated moving average (ARIMA) model was used to quantify the relationship between each independent variable, ED revenue, and visitor volume. The accuracies were evaluated by comparing model forecasts to actual values with mean absolute percentage of error. Sensitivity of prediction errors to model training time was also evaluated. The ARIMA models indicated that mean maximum temperature, relative humidity, rainfall, non-trauma, and trauma visits may correlate positively with ED revenue, but mean minimum temperature may correlate negatively with ED revenue. Moreover, mean minimum temperature and stock market index fluctuation may correlate positively with trauma visitor volume. Mean maximum temperature, relative humidity and stock market index fluctuation may correlate positively with non-trauma visitor volume. Mean maximum temperature and relative humidity may correlate positively with pediatric visitor volume, but mean minimum temperature may correlate negatively with pediatric visitor volume. The model also performed well in forecasting revenue and visitor volume.

Aneurismal subarachnoid hemorrhage in a Chilean population, with emphasis on risk factors

Background

Subarachnoid Hemorrhage (SAH) is caused principally by the rupture of intracranial aneurisms. Important risk factors have been described such as age, sex, hypertension (HT) and season of the year, among others. The objective is to investigate the demographic characteristics and possible risk factors in a population of Chilean patients.

Methods

This retrospective study was based on the analysis of 244 clinical records of patients diagnosed with aneurismal SAH who were discharged from the Instituto de Neurocirugía ASENJO in Santiago, Chile.

Results

The mean age of patients was 49.85 years and the male:female ratio was 1:2.7. The signs and symptoms were not different between sexes; cephalea (85.7%) was predominant, followed by loss of consciousness, vomiting/nausea and meningeal signs. Risk factors included sex, age and HT. Concordant with other reports, the incidence of SAH was greatest in spring.

Conclusions

The demographic characteristics and risk factors observed in patients with aneurismal SAH treated in ASENJO were comparable to those of other populations. We were not able to conclude that tobacco and alcohol consumption were risk factors for this population.

An analysis of admissions from 155 United States hospitals to determine the influence of weather on stroke incidence

Weather is the most frequently proposed factor driving apparent seasonal trends in stroke admissions. Here, we present the largest study of the association between weather and ischemic stroke in the USA to date. We consider admissions to 155 United States hospitals in 20 states during the five-year period from 2004 to 2008. The data set included 196,439 stroke admissions, which were classified as ischemic (n=98,930), hemorrhagic (n=18,960), or transient ischemic attack (n=78,549). Variations in stroke admissions were tested to determine if they tracked seasonal and transient weather patterns over the same time period. Using autocorrelation analyses, no significant seasonal changes in stroke admissions were observed over the study period. Using time-series analyses, no significant association was observed between any weather variable and any stroke subtype over the five-year study. This study suggests that seasonal associations between weather and stroke are highly confounded, and an association between weather and stroke is virtually non-existent. Therefore, previous studies reporting an association between specific weather patterns and stroke should be interpreted with caution.

The Association Between Weather and Spontaneous Subarachnoid Hemorrhage: An Analysis of 155 US Hospitals

BACKGROUND:

A seasonal and meteorological influence on the incidence of spontaneous subarachnoid hemorrhage (SAH) has been suggested, but a consensus in the literature has yet to emerge.

OBJECTIVE:

This study examines the impact of weather patterns on the incidence of SAH using a geographically broad analysis of hospital admissions and represents the largest study of the topic to date.

METHODS:

We retrospectively analyzed SAH admissions to 155 US hospitals during the calendar years 2004 to 2008 (N = 7758). Daily weather readings for temperature, pressure, and humidity were obtained for the same period from National Oceanic and Atmospheric Administration weather stations located near each hospital. The daily values of each weather variable were associated with the daily volume of SAH admissions using a combination of correlation and time-series analyses.

RESULTS:

No seasonal trends were observed in the monthly volume of SAH admissions during the study period. No significant correlation was detected between the daily SAH admission volume and the day's weather, the previous day's weather, or the 24-hour weather change.

CONCLUSION:

This study represents the most comprehensive investigation of the association between weather and spontaneous SAH to date. The results suggest that neither season nor weather significantly influences the incidence of SAH.