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

Influence of meteorological changes on the occurrence of cerebral aneurysm rupture in the Montpellier region: A retrospective study

BACKGROUND/CONTEXT

Aneurysmal subarachnoid hemorrhage (aSAH) is a sudden and potentially serious event. Recognized risk factors of aSAH include smoking, high blood pressure, and alcohol consumption. Some studies have reported associations between risk of aSAH and climatic conditions, but no consensus exists. This study aimed to investigate the association between aSAH and meteorological conditions.

METHODS

We retrospectively included patients admitted for aSAH at Montpellier University Hospital between 2018-2022. We analyzed the correlation between the occurrence of aSAH and several meteorological factors, including precipitation, temperature, barometric pressure, wind speed, humidity, sunshine duration, and storms, within 24 h and 7 days before symptom onset. We collected meteorological data for days without aSAH cases as controls. A multivariate logistic regression with 10-block cross-validation and a penalty lasso method was performed.

RESULTS

For the 5-year period, 492 patients were analyzed. Incident cases per month in this period was higher in February and August and the highest in winter. Diagnoses were made predominantly between noon and midnight. The multivariate model based on 9 weather variables on the days preceding the aSAH event had an accuracy of 0.55. The area under the curve was 0.58 (95% CI 0.55-0.62). The barometric pressure was similar between aSAH days and the mean of the 5 preceding days.

CONCLUSION

Due to the low accuracy of the statistical model, our study could not provide evidence of a link between weather variables and occurrence of aSAH. This issue requires further investigation and reliable epidemiological data to fully understand the pathophysiology and real impact of weather on aSAH.

Association between short-term exposure to meteorological factors on hospital admissions for hemorrhagic stroke: an individual-level, case-crossover study in Ganzhou, China

BACKGROUND

Hemorrhagic stroke (HS) is associated with significant disability and mortality. However, the relationship between meteorological factors and hemorrhagic stroke, as well as the potential moderating role of these factors, remains unclear.

METHODS

Daily data on HS, air pollution, and meteorological conditions were collected from January 2015 to December 2021 in Ganzhou to analyze the relationship between meteorological factors and HS admissions. This analysis employed a time-stratified case-crossover design in conjunction with a distributional lag nonlinear model. Additionally, a bivariate response surface modelling was utilized to further investigate the interaction between meteorological factors and particulate matter. The study also stratified the analyses by gender and age. To investigate the potential impact of extreme weather conditions on HS, this study defined the 97.5th percentile as representing extremely high weather conditions, while the 2.5th percentile was classified as extremely low.

RESULTS

In single-day lags, the risk of admissions for HS was significantly associated with extremely low temperature (lag 1-2 and lag 13-14), extremely low humidity (lag 1 and lag 9-12), and extremely high precipitation (lag 2-7). Females exhibited greater susceptibility to extremely low temperature than males within the single-day lag pattern in the subcomponent layer, with a maximum relative risk (RR) that was 7% higher. In the cumulative lag analysis, the risk of HS admissions was significantly associated with extremely high temperature (lag 0-8∼lag 0-14), extremely low humidity (lag 0-2∼lag 0-14), and extremely high precipitation (lag 0-4∼lag 0-14). Within the cumulative lag day structure of the subcomponent layer, both extremely low and extremely high temperature had a more pronounced effect on females and aged ≥65 years. The risk of HS admissions was positively associated with extremely high barometric pressure in the female subgroups (lag 0-1 and lag 0-2). The highest number of HS admissions occurred when high PM2.5 concentrations coexisted with low precipitation.

CONCLUSIONS

Meteorological factors were significantly associated with the risk of hospital admissions for HS. Individuals who were female and aged ≥65 years were found to be more susceptible to these meteorological influences. Additionally, an interaction was observed between airborne particulate matter and meteorological factors. These findings contributed new evidence to the association between meteorological factors and HS.

Subarachnoid Haemorrhage Incidence Pattern Analysis with Circular Statistics

Knowledge about biological rhythms of diseases may not only help in understanding the pathophysiology of diseases but can also help health service policy makers and emergency department directors to allocate resources efficiently. Aneurysmal subarachnoid haemorrhage (SAH) has high rates of morbidity and mortality. The incidence of SAH has been attributed to patient-related factors such as characteristics of aneurysms, smoking, and hypertension. There are studies showing that the incidence of aneurysmal SAH appears to behave in periodic fashions over long time periods. However, there are inconsistencies in the literature regarding the impact of chronobiological factors such as circadian, seasonal, and lunar cycle factors on the occurrence of SAH. In this study, we focused on the analysis of a temporal pattern of SAH (infradian rhythms) with a novel approach using circular statistical methods. We aimed to see whether there is a circular pattern for the occurrence of SAH at all and if so, whether it can be related to known temporal patterns based on available literature. Our study did not support the notion that aneurysmal subarachnoid haemorrhages occur on any specific day in a cycle with specific lengths up to 365 days including specific weekdays, full moon, equinoxes, and solstices. Hence, we found no relationship between SAH incidence and timing. Study in larger populations using similar circular statistical methods is suggested.

A Comparison of Perioperative Complications and Outcomes in Patients Undergoing Cerebral Aneurysm Clipping Performed Ultra-Early (≤ 24 hours) versus Late (> 24 hours): A 7-Year Retrospective Study of 302 Patients

Objectives  The intracerebral aneurysm with subarachnoid hemorrhage (SAH) has a high morbidity and mortality rate. This study aimed to compare the incidences of perioperative complications in ultra-early surgery (within 24 hours) with those in late surgery (> 24 hours). Methods  Retrospective data were reviewed for 302 patients who underwent craniotomies with aneurysm clipping between January 2014 and December 2020. Perioperative data were obtained from the medical records and reviewed by the investigators. The complications were compared between ultra-early and late operations. We were interested in major complications such as delayed ischemic neurologic deficit (DIND), intraoperative aneurysm rupture (IAR), and anesthesia-related complications. The short-term (in hospital) and long-term (1 year) outcomes in patients with or without DIND and IAR were compared. The collected data was statistically analyzed. Results  Three hundred and two patients were analyzed, and 264 patients had completed follow-up. The ultra-early cases (150 patients) had a higher American Society of Anesthesiologists physical status, a lower Glasgow Coma Scale, and higher Hunt and Hess scales. The surgeons operated on more cases of the anterior cerebral artery as ultra-early operations. The incidence rates of DIND, IAR, severe hemodynamic instability, and cardiac arrest were 5.6, 8.3, 6.3, and 0.3%, respectively, which were not different between groups. However, the reintubation rate was higher in the ultra-early surgery cases (0 vs. 3.3%, p  = 0.023). The DIND and IAR patients had poorer short-term (in hospital) outcomes. Conclusions  There were no differences in major complications between ultra-early and late craniotomy with aneurysm clipping. However, the reintubation rate was strikingly higher in the ultra-early group. Patients with major complications had early, unfavorable outcomes.

Re-Evaluating Risk Factors, Incidence, and Outcome of Aneurysmal and Non-Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

Subarachnoid hemorrhage (SAH) is one of the world's most life-threatening types of stroke. SAH can be classified into two main categories, aneurysmal (aSAH) and non-aneurysmal SAH (naSAH). In the present study, we aimed to prospectively evaluate SAH and its subcategories incidences, risk factors, complications, and outcomes in central Iran.

METHODS

All SAH patients diagnosed between 2016 and 2020 were included in Isfahan SAH Registry. Demographic, clinical characteristics, incidence rates (based on age categories), and laboratory/imaging findings were collected and compared between aSAH and naSAH subgroups. Complications during hospital stay and outcomes were also analyzed. Binary logistic regression analysis was performed to investigate the predictors of aSAH versus naSAH. Kaplan-Meier curves and Cox regression were used to evaluate the survival probability.

RESULTS

A total of 461 SAH patients were included through Isfahan SAH Registry. The SAH annual incidence rate was 3.11 per 100,000 person-years. aSAH had higher incidence rate than naSAH (2.08/100,000 vs. 0.9/100,000 person-years, respectively). In-hospital mortality was 18.2%. Hypertension (P = 0.003) and smoking (P = 0.03) were significantly associated with aSAH, whereas diabetes mellitus (P < 0.001) was more associated with naSAH. After Cox regression analysis, there were higher hazard ratios for reduced in-hospital survival in conditions including altered mental status, Glasgow Coma Scale ≤13, rebleeding, and seizures.

CONCLUSIONS

This study provided an updated estimation of SAH and its subgroups incidences in central Iran. Risk factors for aSAH are comparable to the ones reported in the literature. It is noteworthy that diabetes mellitus was associated with a higher incidence of naSAH in our cohort.

Associations between meteorological variation and rupture of intracranial aneurysm in Fujian, China: A 5-year multicenter study

OBJECTIVE

By exploring the exposure-response relationships between meteorological factors and rupture of intracranial aneurysm (IA) to reveal the influence of meteorological variation on IA rupture under the specific climate in Fujian, China.

METHOD

7515 cases of IA rupture from several municipal medical institutions in Fujian Province as well as local meteorological data during the same period were collected from 2013 to 2017. Poisson regression and Spearman correlation analysis were applied to explore the distribution characteristics of IA rupture and how it is associated with meteorological parameters. Poisson generalized additive model was established to further analyze the exposure-response relationships between meteorological factors and IA rupture, and its hysteresis effects.

RESULT

The IA rupture exhibited a negative correlation with temperature (r_s = -0.323, 95% CI: -0.539 ~ -0.068) and a positive correlation with atmospheric pressure (r_s = 0.397, 95% CI: 0.152-0.597) or pressure difference (r_s = 0.296, 95% CI: 0.038-0.517), 21.05 ℃ and 1000.14 hPa were the risk thresholds for the onset ascribed to variation in temperature and atmospheric pressure, respectively. Temperature and atmospheric pressure also exerted hysteresis effects on IA rupture. Cold will increase the rupture risk in the subsequent 1-3 days, and high pressure will raise the morbidity in the next 1-2 days. Besides, drastic variations in temperature and atmospheric pressure were also associated with the higher risk of IA rupture in the next 2 days and 1 day, respectively.

CONCLUSION

Temperature and atmospheric pressure have a negative and positive correlation with IA rupture in Fujian, China, respectively. Variation in temperature and atmospheric pressure exert different degrees of hysteresis effects on IA rupture.

Weather conditions associated with subarachnoid hemorrhage: a multicenter case-crossover study

BACKGROUND

Most spontaneous subarachnoid hemorrhages (SAH) occur unexpectedly and independently of classical risk factors. In the light of increasing climate variability and change, we investigated weather and rapid weather changes as possible short-term risk factors for SAH.

METHODS

Seven hundred ninety one patients admitted to three major hospitals in Germany for non-traumatic SAH with a determinable onset of SAH symptoms were included in this hospital-based, case-crossover study. The effects of atmospheric pressure, relative air humidity, and ambient temperature and their 24 h changes on the onset of SAH under temperate climate conditions were estimated.

RESULTS

There was no association between the risk of SAH and 24 h weather changes, mean daily temperature or mean relative air humidity in the overall population. For every 11.5 hPa higher mean daily atmospheric pressure, the risk of SAH increased by 15% (OR 1.15, 95% confidence interval (CI) 1.01-1.30) in the entire study population with a lag time of three days.

CONCLUSION

Our results suggest no relevant association between 24 h-weather changes or absolute values of ambient temperature and relative humidity and the risk of SAH. The medical significance of the statistically weak increase in SAH risk three days after exposure to high atmospheric pressure is unclear. However, as the occurrence of stable high-pressure systems will increase with global warming and potentially affect SAH risk, we call for confirming studies in different geographical regions to verify our observations.

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.

Neurobehavioral Deficits After Subarachnoid Hemorrhage in Mice: Sensitivity Analysis and Development of a New Composite Score

Background

Because of the failure of numerous clinical trials, various recommendations have been made to improve the usefulness of preclinical studies. Specifically, the STAIR (Stroke Therapy Academic Industry Roundtable) recommendations highlighted functional outcome as a critical measure. Recent reviews of experimental subarachnoid hemorrhage (SAH) studies have brought to light the numerous neurobehavioral scoring systems that are used in preclinical SAH studies. To gain insight into the utility of these scoring systems, as well as to identify a scoring system that best captures the deficits caused by SAH in mice, we designed the current study.

Methods and Results

Adult male C57BL/6J mice were used. One cohort of mice was randomly allocated to either sham or SAH and had functional testing performed on days 1 to 3 post‐SAH using the modified Bederson Score, Katz Score, Garcia Neuroscore, and Parra Neuroscore, as well as 21 individual subtests. A new composite neuroscore was developed using the 8 most diagnostically accurate subtests. To validate the use of the developed composite neuroscore, another cohort of mice was randomly assigned to either the sham or SAH group and neurobehavior was evaluated on days 1 to 3, 5, and 7 after injury. Receiver operating characteristic curves were used to analyze the diagnostic accuracy of each scoring system, as well as the subtests. Of the 4 published scoring systems, the Parra Neuroscore was diagnostically accurate for SAH injury in mice versus the modified Bederson and Katz Scores, but not the Garcia Neuroscore. However, the newly developed composite neuroscore was found to be statistically more diagnostically accurate than even the Parra Neuroscore.

Conclusions

The findings of this study promote use of the newly developed composite neuroscore for experimental SAH studies in mice.

The Time-Related Trends in the Presenting of Traumatic Head Injury in a Single Institution

Objective

It is important to know the epidemiologic aspects of traumatic brain injury (TBI) for its rapid detection, appropriate treatment, and prevention. The purpose of this study is to classify the time of arrival of patients in the emergency room (ER) by time of day, day of the week, month, and season, and to analyze the relationship between the frequency of presentation at different times and TBI.

Methods

The time of arrival of 327 patients with TBI between January 2016 to December 2017 at the ER was analyzed retrospectively. The trends regarding the frequency of presentation of patients with TBI were analyzed in relation to arrival time at the ER.

Results

Patients with TBI were found to have the greatest number of hospitalizations at 13:00–18:00, on Saturdays, in December, and during the summer. Surgical treatment was not related to the temporal pattern of TBI patient admission. Patients with TBI in the severe group (GCS score <8) arrived at the ER mainly at 07:00–12:00 (p=0.015). Patients with TBI in the mild group (GCS score 13–15) mainly presented in the ER during the summer (p=0.003), while patients TBI in the moderate group (GCS score 9–12) presented mainly in the winter (p=0.244). The combination of the mild and moderate group presented more often in the winter (p=0.014).

Conclusion

It is worthwhile understanding the temporal trends of TBI patients. These data may provide useful information in predicting the ER visits of TBI patients in advance and preparing for prompt and appropriate treatment.

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.

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.

Comparative Outcomes of Respiratory Failure Associated with Common Neuromuscular Emergencies: Myasthenia Gravis versus Guillain-Barré Syndrome

Background and objectives: Myasthenia gravis (MG) and Guillain-Barré Syndrome (GBS) are autoimmune neuromuscular disorders that may present as neuromuscular emergencies requiring mechanical ventilation and critical care. Comparative outcomes of these disease processes, once severe enough to require mechanical ventilation, are not known. In this study, we compared the patients requiring mechanical ventilation in terms of in-hospital complications, length of stay, disability, and mortality between these two disease entities at a national level. Materials and Methods: Mechanically ventilated patients with primary diagnosis of MG (n = 6684) and GBS (n = 5834) were identified through retrospective analysis of Nationwide Inpatient Sample (NIS) database for the years 2006 to 2014. Results: Even though mechanically ventilated MG patients were older (61.0 ± 19.1 versus 54.9 ± 20.1 years) and presented with more medical comorbidities, they had lower disease severity on admission, as well as lower in-hospital complications sepsis, pneumonia, and urinary tract infections as compared with GBS patients. In the multivariate analysis, after adjusting for confounders including treatment, GBS patients had significantly higher disability (odds ratio (OR) 15.6, 95% confidence interval (CI) 10.9-22.2) and a longer length of stay (OR 3.48, 95% CI 2.22-5.48). There was no significant difference in mortality between the groups (8.45% MG vs. 10.0% GBS, p = 0.16). Conclusion: Mechanically ventilated GBS patients have higher disease severity at admission along with more in-hospital complications, length of stay, and disability compared with MG patients. Potential explanations for these findings include delay in the diagnosis, poor response to immunotherapy particularly in patients with axonal GBS variant, or longer recovery time after nerve damage.

Racial/ethnic disparities in hospital utilization in intracerebral hemorrhage

Background and purpose

There is evidence that racial and ethnic differences among intracerebral hemorrhage (ICH) patients exist. We sought to establish the occurrence of disparities in hospital utilization in the United States.

Methods

We identified ICH patients from United States Nationwide Inpatient Sample database for years 2006–2014 using codes (DX1 = 431, 432.0) from the International Classification of Diseases, 9th edition. We compared five race/ethnic categories: White, Black, Hispanic, Asian or Pacific Islander, and Others ( Native American and other) with regard to demographics, comorbidities, disease severity, in-hospital complications, in-hospital procedures, length of stay (LOS), total hospital charges, in-hospital mortality, palliative care, (PC) and do not resuscitate (DNR). We categorized procedures as lifesaving (i.e. ventriculostomy, craniotomy, craniectomy, and ventriculoperitoneal (VP) shunt), life sustaining (i.e. mechanical ventilation, tracheostomy, transfusions, and gastrostomy). White race/ethnicity was set as the reference group.

Results

Out of 710,293 hospitalized patients with ICH 470,539 (66.2%), 114,821 (16.2%), 66,451 (9.3%), 30,297 (4.3%) and 28,185 (3.9%) were White, Black, Hispanic, Asian or Pacific Islander, and Others, respectively. Minorities (Black, Hispanic, Asian or Pacific Islander, and Others) had a higher rate of in-hospital complications, in-hospital procedures, mean LOS, and hospital charges compared to Whites. In contrast, Whites had a higher rate of in-hospital mortality, PC, and DNR. In multivariable analysis, all minorities had higher rate of MV, tracheostomy, transfusions, and gastrostomy compared to Whites, while Hispanics had higher rate of craniectomy and VP shunt; and Asian or Pacific Islander and Others had higher rate of craniectomy. Whites had a higher rate of in-hospital mortality, palliative care, and DNR compared to minorities. In mediation analysis, in-hospital mortality for whites remained high after adjusting with PC and DNR.

Conclusion

Minorities had greater utilization of lifesaving and life sustaining procedures, and longer LOS. Whites had greater utilization of palliative care, hospice, and higher in-hospital mortality. These results may reflect differences in culture or access to care and deserve further study.

Hypernatremia is associated with poorer outcomes following aneurysmal subarachnoid hemorrhage: a nationwide inpatient sample analysis

BACKGROUND

Hypernatremia is one of the most common electrolyte disturbances following aneurysmal subarachnoid hemorrhage (aSAH) and has been correlated with increased mortality in single institution studies. We investigated this association using a large nationwide healthcare database.

METHODS

We performed a retrospective analysis of adults between 2002 and 2011 with a primary diagnosis of aSAH using the Nationwide Inpatient Sample (NIS). Patients were grouped according to whether or not an inpatient diagnosis of hypernatremia was present. The primary outcome was the NIS-SAH outcome measure. Secondary outcomes included in-hospital mortality, length of stay (LOS), and non-routine hospital discharge. Outcomes analyses adjusted for SAH severity using the NIS-SAH Severity Score, Charlson Comorbidity Index, and the presence of cerebral edema.

RESULTS

A total of 18,377 patients were included in the study. The incidence of a poor outcome as defined by the NIS-SAH outcome measure was 65.9% in the hypernatremia group and 33.4% in the normonatremia group (OR 1.96, 95% CI 1.68 - 2.27). There was higher mortality in the hypernatremia group (OR 1.60, 95% CI 1.37 - 1.87). Patients with hypernatremia had a significantly higher rate of non-routine hospital discharge and gastrostomy. The incidences of poor outcome, in-hospital mortality, and non-routine disposition were higher in the hypernatremia group regardless of treatment type (clipping vs. endovascular embolization). Pulmonary complications and acute kidney injury were more common in the hypernatremia group as well.

CONCLUSIONS

In patients with aSAH, hypernatremia is associated with poorer functional outcomes regardless of SAH severity.

Cerebrovascular diseases in Poland-inconsistent seasonal patterns of hospitalisation and mortality

Background

A seasonal variation in the incidence of cerebrovascular diseases still remains inconsistently evidenced. Herein, we analyse the monthly patterns of two health phenomena: hospital admissions and deaths due to these diseases.

Methods

We identified 69 511 cases of hospital admissions and 14 956 deaths due to cerebrovascular diseases (ICD10: I60-I69 and G45) among the inhabitants of five Polish voivodeship capitals in 2004-13. The method of time series analysis (exponential smoothing with linear trend and monthly additive seasonality) was applied to calculate the monthly specific seasonal indices. The monthly variation in an in-hospital fatality and nonhospital deaths were also analysed.

Results

A summer season reduction in number of cases was observed for hospital admissions and deaths. Interestingly, the winter season effect is much more complex, mainly due to the contribution of December, when a high mortality is accompanied by a substantial decrease in the hospitalisation level. This unique discrepancy was observed for all the studied cities. Moreover, this month is characterised by a notably high in-hospital fatality. However, neither the number of non-hospital deaths nor the average length of hospital stay or the kind of hospitalised diseases evidenced that cerebrovascular problems were more serious in December than in any other month.

Conclusion

The obtained results confirmed a seasonal variation in cerebrovascular diseases among the inhabitants of Polish cities. Habitual and administrative limitations in hospital activities observed every December do not seem indifferent from the patient health's perspective since they may lead to a low hospitalisation level and a high in-hospital fatality.

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.

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.

Oceanic Meteorological Conditions Influence Incidence of Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

Publications concerning the weather pattern of occurrence of the subarachnoid hemorrhage have produced controversial results. We chose to study subarachnoid hemorrhage occurring in oceanic climate with deep variations focusing on partial oxygen volume (pO₂) and patient history.

METHODS

Seventy-one patients had been successively recruited from a single center 45 km from the Atlantic shore. Climate conditions had been analyzed from 72 hours before subarachnoid hemorrhage to 24 hours after. According to Dalton's law, climate conditions influence pO_2, recalculated with Dupré's formula, and patient history analyzed and scored according to the induced oxidative stress.

RESULTS

Subarachnoid hemorrhage risk is highest during spring and autumn, lowest between midnight and 6:00 a.m. Risk is highest after a period of atmospheric pressure higher than 1010 hPa (83%) and high pO₂ and lowest for atmospheric pressure lower than 990 hPa and pO₂ lower than 20.6_. According to the medical history, 2 groups of patients could be identified: patients without history (22%), women (62%), high atmospheric pressure, and relatively lower pO₂; and patients with a medical history, relatively lower atmospheric pressure, and higher pO₂. Atmospheric pressure decreased significantly before disruption (994 hPa) but with a constant pO₂. Subarachnoid hemorrhages during high atmospheric pressure were preceded by a decrease of pO₂ despite a highly stable period of high atmospheric pressure.

DISCUSSION

Atmospheric O₂ changes and the subsequent oxidative stress could be the local ultimate trigger of subarachnoid hemorrhage that could result in the "ideal" fit of patient's health conditions with the meteorological environment.

Seasonal and Monthly variation in stroke and its subtypes-10 Year Hospital-Based Study

Background and Objectives:

There is no evidence of long-term studies of seasonal variations in stroke in Iran. Hence, the aim of this study was to determine the seasonal and monthly variation of 28-day mortality in Isfahan, Iran.

Methods:

From 2003 to 2013, In a Hospital-based retrospective study which was conducted by Isfahan Cardiovascular Research Center(ICRC), 24186 cases with first-ever stroke were recruited. Multinomial logistic regression was used to calculate odds ratios (OR) with 95% confidence intervals (CI) for seasonal and monthly 28-day mortality for stroke in general and three subtypes of stroke including intracranial hemorrhage (ICH), ischemic (IS) and subarachnoid hemorrhage (SAH).

Results:

In this study, unadjusted and adjusted odds ratios of seasonal 28-day mortality of stroke was highest in the winter and lowest in the summer. Although, differences were not statistically significant. For total and IS stroke, the unadjusted 28-day mortality ratio (UMR) was significant in February (1.19, 95% CI 1.00 -1.42, P= 0.04) as compared to March. Whereas after adjusted, for total stroke, 28-day mortality was significantly lowest in May (0.746, 95% CI 0.575-0.97, p=0.029), June (0.777, 95% CI 0.60-0.99, p=0.49) and July (0.771, 95% CI 0.59-0.99 p=0.049) as compared to March. The AMR between months were not significant in SAH and IS.

Conclusion:

Our findings demonstrate clear obvious monthly variation of 28-day mortality of stroke and its subtypes in Isfahan but no seasonal variations were observed.

Increased incidence of subarachnoid hemorrhage during cold temperatures and influenza epidemics

OBJECTIVE

This study investigated whether the increased incidence of aneurysmal subarachnoid hemorrhage (SAH) in winter is related to temperature or increased incidence of influenza. Such relationships may elucidate the pathogenesis of intracranial aneurysm rupture.

METHODS

A nationwide sample of 18,714 patients with SAH was linked with weekly temperature and influenza-like illness consultation data. Poisson regression analyses were used to calculate incidence density ratios (IDRs) with corresponding 95% CIs for the association of SAH incidence with temperature and influenza epidemics; IDRs were adjusted for study year (aIDR). In addition, SAH incidence data from 30 European population-based studies were linked with daily temperature data from the European Climate Assessment.

RESULTS

The aIDR for SAH during influenza epidemics was 1.061 (95% CI 1.022–1.101) in the univariable and 1.030 (95% CI 0.989–1.074) in the multivariable analysis. This association declined gradually during the weeks after epidemics. Per 1°C temperature drop, the aIDR was 1.005 (95% CI 1.003–1.008) in the univariable and 1.004 (95% CI 1.002–1.007) in the multivariable analysis. In the European population-based studies, the IDR was 1.143 (95% CI 1.129–1.157) per 1°C temperature drop.

CONCLUSIONS

The incidence of SAH is increased during cold temperatures and epidemic influenza. Future studies with individual patient data are needed to investigate causality between temperature or influenza and SAH.

Long-term changes in the heat-mortality relationship according to heterogeneous regional climate: a time-series study in South Korea

OBJECTIVES

Several studies identified a heterogeneous impact of heat on mortality in hot and cool regions during a fixed period, whereas less evidence is available for changes in risk over time due to climate change in these regions. We compared changes in risk during periods without (1996-2000) and with (2008-2012) heatwave warning forecasts in regions of South Korea with different climates.

METHODS

Study areas were categorised into 3 clusters based on the spatial clustering of cooling degree days in the period 1993-2012: hottest cluster (cluster H), moderate cluster (cluster M) and cool cluster (cluster C). The risk was estimated according to increases in the daily all-cause, cardiovascular and respiratory mortality per 1°C change in daily temperature above the threshold, using a generalised additive model.

RESULTS

The risk of all types of mortality increased in cluster H in 2008-2012, compared with 1996-2000, whereas the risks in all-combined regions and cooler clusters decreased. Temporal increases in mortality risk were larger for some vulnerable subgroups, including younger adults (<75 years), those with a lower education and blue-collar workers, in cluster H as well as all-combined regions. Different patterns of risk change among clusters might be attributable to large increases in heatwave frequency or duration during study periods and the degree of urbanisation in cluster H.

CONCLUSIONS

People living in hotter regions or with a lower socioeconomic status are at higher risk following an increasing trend of heat-related mortality risks. Continuous efforts are needed to understand factors which affect changes in heat-related mortality risks.

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.

High Subarachnoid Hemorrhage Patient Volume Associated With Lower Mortality and Better Outcomes

BACKGROUND

High-volume centers have better outcomes than low-volume centers when managing complex conditions including subarachnoid hemorrhage (SAH).

OBJECTIVE

To quantify SAH volume-outcome association and determine the extent to which this association is influenced by aggressiveness of care.

METHODS

A serial cross-sectional retrospective study using the Nationwide Inpatient Sample for 2002 to 2010 was performed. Included were all adult (older than 18 years of age) discharged patients with a primary diagnosis of SAH admitted from the emergency department or transferred to a discharging hospital; cases of trauma or arteriovenous malformation were excluded. Survey-weighted descriptive statistics estimated temporal trends. Multilevel logistic regression estimated volume-outcome associations for inpatient mortality and discharge home. Models were adjusted for demographic characteristics, year, transfer status, insurance status, all individual Charlson comorbidities, intubation, and all patient-refined, diagnosis-related group mortality. Analyses were repeated, excluding cases in which aggressive care was not pursued.

RESULTS

A total of 32,336 discharges were included; 13,398 patients underwent clipping (59.1%) or coiling (40.9%). The inpatient mortality rate decreased from 32.2% in 2002 to 22.2% in 2010; discharge home increased from 28.5% to 40.8% during the same period. As SAH volume decreased from 100/year, the mortality rate increased from 18.7% to 19.8% at 80/year, 21.7% at 60/year, 24.5% at 40/year, and 28.4% at 20/year. As SAH patient volume decreased, the probability of discharge home decreased from 40.3% at 100/year to 38.7% at 60/year, and 35.3% at 20/year. Better outcomes persisted in patients receiving aggressive care and in those not receiving aggressive care.

CONCLUSION

Short-term SAH outcomes have improved. High-volume hospitals have more favorable outcomes than low-volume hospitals. This effect is substantial, even for hospitals conventionally classified as high volume.

Effect of seasonal and monthly variation in weather and air pollution factors on stroke incidence in Seoul, Korea

BACKGROUND AND PURPOSE

The purpose of the present study was to determine whether seasonal and monthly variations in stroke incidence exist and whether they are related to meteorologic and air pollution parameters under similar weather and environmental conditions in selected areas of Seongdong district, Seoul, South Korea.

METHODS

From January 1, 2004, to December 31, 2013, 3001 consecutive stroke events were registered in residents of selected areas of Seongdong district, Seoul, South Korea. The authors calculated the stroke attack rate per 100,000 people per month and the relative risk of stroke incidence associated with meteorologic and air pollution parameters. We also analyzed odds ratios with a 95% confidence interval for seasonal and monthly stroke incidence.

RESULTS

The incidence of stroke in September was significantly higher (odds ratio, 1.233; 95% confidence interval, 1.042-1.468) compared with January. The seasonal ischemic stroke incidence in summer (odds ratio, 1.183; 95% confidence interval, 1.056-1.345) was significantly higher than in winter, whereas the seasonal incidence of intracerebral hemorrhage relative to winter was not significant. The mean temperature was positively correlated with ischemic stroke (relative risk, 1.006; P=0.003), and nitrogen dioxide (relative risk, 1.262; P=0.001) showed a strong positive correlation with intracerebral hemorrhage incidence among the older age group.

CONCLUSIONS

We demonstrated distinct patterns of seasonal and monthly variation in the incidence of stroke and its subtypes through consideration of the meteorologic and air pollution parameters. We therefore expect that these findings may enhance our understanding of the relationships between stroke and weather and pollutants.

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.

Analysis of subarachnoid hemorrhage using the Nationwide Inpatient Sample: the NIS-SAH Severity Score and Outcome Measure

Object

Studies using the Nationwide Inpatient Sample (NIS), a large ICD-9–based (International Classification of Diseases, Ninth Revision) administrative database, to analyze aneurysmal subarachnoid hemorrhage (SAH) have been limited by an inability to control for SAH severity and the use of unverified outcome measures. To address these limitations, the authors developed and validated a surrogate marker for SAH severity, the NIS-SAH Severity Score (NIS-SSS; akin to Hunt and Hess [HH] grade), and a dichotomous measure of SAH outcome, the NIS-SAH Outcome Measure (NIS-SOM; akin to modified Rankin Scale [mRS] score).

Methods

Three separate and distinct patient cohorts were used to define and then validate the NIS-SSS and NIS-SOM. A cohort (n = 148,958, the “model population”) derived from the 1998–2009 NIS was used for developing the NIS-SSS and NIS-SOM models. Diagnoses most likely reflective of SAH severity were entered into a regression model predicting poor outcome; model coefficients of significant factors were used to generate the NIS-SSS. Nationwide Inpatient Sample codes most likely to reflect a poor outcome (for example, discharge disposition, tracheostomy) were used to create the NIS-SOM.

Data from 716 patients with SAH (the “validation population”) treated at the authors' institution were used to validate the NIS-SSS and NIS-SOM against HH grade and mRS score, respectively.

Lastly, 147,395 patients (the “assessment population”) from the 1998–2009 NIS, independent of the model population, were used to assess performance of the NIS-SSS in predicting outcome. The ability of the NIS-SSS to predict outcome was compared with other common measures of disease severity (All Patient Refined Diagnosis Related Group [APR-DRG], All Payer Severity-adjusted DRG [APS-DRG], and DRG).

Results

The NIS-SSS significantly correlated with HH grade, and there was no statistical difference between the abilities of the NIS-SSS and HH grade to predict mRS-based outcomes. As compared with the APR-DRG, APSDRG, and DRG, the NIS-SSS was more accurate in predicting SAH outcome (area under the curve [AUC] = 0.69, 0.71, 0.71, and 0.79, respectively).

A strong correlation between NIS-SOM and mRS was found, with an agreement and kappa statistic of 85% and 0.63, respectively, when poor outcome was defined by an mRS score > 2 and 95% and 0.84 when poor outcome was defined by an mRS score > 3.

Conclusions

Data in this study indicate that in the analysis of NIS data sets, the NIS-SSS is a valid measure of SAH severity that outperforms previous measures of disease severity and that the NIS-SOM is a valid measure of SAH outcome. It is critically important that outcomes research in SAH using administrative data sets incorporate the NIS-SSS and NIS-SOM to adjust for neurology-specific disease severity.

Patient outcomes following subarachnoid hemorrhage between the medical center and regional hospital: whether all patients should be transferred to medical centers

Subarachnoid hemorrhage (SAH) is a critical illness that may result in patient mortality or morbidity. In this study, we investigated the outcomes of patients treated in medical center and nonmedical center hospitals and the relationship between such outcomes and hospital and surgeon volume. Patient data were abstracted from the National Health Insurance Research Database of Taiwan in the Longitudinal Health Insurance Database 2000, which contains all claims data of 1 million beneficiaries randomly selected in 2000. The International Classification of Diseases, Ninth Revision, subarachnoid hemorrhage (430) was used for the inclusion criteria. We identified 355 patients between 11 and 87 years of age who had subarachnoid hemorrhage. Among them, 32.4% (115/355) were men. The median Charlson comorbidity index (CCI) score was 1.3 (SD ± 0.6). Unadjusted logistic regression analysis demonstrated that low mortality was associated with high hospital volume (OR = 3.21; 95% CI: 1.18–8.77). In this study, we found no statistical significances of mortality, LOS, and total charges between medical centers and nonmedical center hospitals. Patient mortality was associated with hospital volume. Nonmedical center hospitals could achieve resource use and outcomes similar to those of medical centers with sufficient volume.

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 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.

Perioperative variables contributing to the rupture of intracranial aneurysm: an update

Background. Perioperative aneurysm rupture (PAR) is one of the most dreaded complications of intracranial aneurysms, and approximately 80% of nontraumatic SAHs are related to such PAR aneurysms. The literature is currently scant and even controversial regarding the issues of various contributory factors on different phases of perioperative period. Thus this paper highlights the current understanding of various risk factors, variables, and outcomes in relation to PAR and try to summarize the current knowledge. Method. We have performed a PubMed search (1 January 1991–31 December 2012) using search terms including “cerebral aneurysm,” “intracranial aneurysm,” and “intraoperative/perioperative rupture.” Results. Various risk factors are summarized in relation to different phases of perioperative period and their relationship with outcome is also highlighted. There exist many well-known preoperative variables which are responsible for the highest percentage of PAR. The role of other variables in the intraoperative/postoperative period is not well known; however, these factors may have important contributory roles in aneurysm rupture. Preoperative variables mainly include natural course (age, gender, and familial history) as well as the pathophysiological factors (size, type, location, comorbidities, and procedure). Previously ruptured aneurysm is associated with rupture in all the phases of perioperative period. On the other hand intraoperative/postoperative variables usually depend upon anesthesia and surgery related factors. Intraoperative rupture during predissection phase is associated with poor outcome while intraoperative rupture at any step during embolization procedure imposes poor outcome. Conclusion. We have tried to create such an initial categorization but know that we cannot scale according to its clinical importance. Thorough understanding of various risk factors and other variables associated with PAR will assist in better clinical management as well as patient care in this group and will give insight into the development and prevention of such a catastrophic complication in these patients.