Dependence of subarachnoid hemorrhage on climate conditions: a systematic meteorological analysis from the dusseldorf metropolitan area

Chronobiological Patterns of Aneurysmal Subarachnoid Hemorrhage in Central China

Background:

Aneurysmal subarachnoid hemorrhage (aSAH) is an acute and sometimes fatal cerebrovascular disease. The chronobiological patterns of aSAH are still unclear worldwide. This 15-year time-series study aims to clarify the chronobiological patterns including seasonal, monthly, weekly, and circadian distributions of aSAH.

Methods:

We retrospectively analyzed the medical records of aSAH patients in central China. To investigate seasonal and weekly distributions, we used the χ2 goodness-of-fit test to analyze the uniformity of the onset time. To explore monthly and circadian distributions, we established Fourier models to show the rhythmicity in chronobiological patterns. Subgroup analyses were conducted to assess the impact of age, gender, hypertension statuses, and aneurysmal characteristics (number, size, and location) on the chronobiological patterns of aSAH.

Results:

A total of 1469 patients with aSAH were recruited in the study. The seasonal and monthly distribution exhibited significantly higher incidence in winter and January/December and lower incidence in summer and July. The weekly distribution of aSAH onset showed no significant uneven variation. The circadian distribution of aSAH exhibited a significant pattern (p = 0.0145), with a morning peak around 8:00, and a late afternoon peak at 16:00–20.00. The circadian rhythmicity varied in subgroups of different ages, genders, and aneurysmal locations.

Conclusion:

The occurrence of aSAH exhibits significant circannual and circadian patterns among the Chinese population. Patients with aSAH of different ages, genders, and aneurysmal locations would present different chronobiological patterns.

Multidimensional Deep Learning Reduces False-Positives in the Automated Detection of Cerebral Aneurysms on Time-Of-Flight Magnetic Resonance Angiography: A Multi-Center Study

Current deep learning-based cerebral aneurysm detection demonstrates high sensitivity, but produces numerous false-positives (FPs), which hampers clinical application of automated detection systems for time-of-flight magnetic resonance angiography. To reduce FPs while maintaining high sensitivity, we developed a multidimensional convolutional neural network (MD-CNN) designed to unite planar and stereoscopic information about aneurysms. This retrospective study enrolled time-of-flight magnetic resonance angiography images of cerebral aneurysms from three institutions from June 2006 to April 2019. In the internal test, 80% of the entire data set was used for model training and 20% for the test, while for the external tests, data from different pairs of the three institutions were used for training and the remaining one for testing. Images containing aneurysms > 15 mm and images without aneurysms were excluded. Three deep learning models [planar information-only (2D-CNN), stereoscopic information-only (3D-CNN), and multidimensional information (MD-CNN)] were trained to classify whether the voxels contained aneurysms, and they were evaluated on each test. The performance of each model was assessed using free-response operating characteristic curves. In total, 732 aneurysms (5.9 ± 2.5 mm) of 559 cases (327, 120, and 112 from institutes A, B, and C; 469 and 263 for 1.5T and 3.0T MRI) were included in this study. In the internal test, the highest sensitivities were 80.4, 87.4, and 82.5%, and the FPs were 6.1, 7.1, and 5.0 FPs/case at a fixed sensitivity of 80% for the 2D-CNN, 3D-CNN, and MD-CNN, respectively. In the external test, the highest sensitivities were 82.1, 86.5, and 89.1%, and 5.9, 7.4, and 4.2 FPs/cases for them, respectively. MD-CNN was a new approach to maintain sensitivity and reduce the FPs simultaneously.

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.

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.

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.

Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Aneurysmal subarachnoid hemorrhage (SAH) is associated with a mortality of more than 30%. Only about 30% of patients with SAB recover sufficiently to return to independent living.

METHODS

This article is based on a selective review of pertinent literature retrieved by a PubMed search.

RESULTS

Acute, severe headache, typically described as the worst headache of the patient's life, and meningismus are the characteristic manifestations of SAH. Computed tomog raphy (CT) reveals blood in the basal cisterns in the first 12 hours after SAH with approximately 95% sensitivity and specificity. If no blood is seen on CT, a lumbar puncture must be performed to confirm or rule out the diagnosis of SAH. All patients need intensive care so that rebleeding can be avoided and the sequelae of the initial bleed can be minimized. The immediate transfer of patients with acute SAH to a specialized center is crucially important for their outcome. In such centers, cerebral aneurysms can be excluded from the circulation either with an interventional endovascular procedure (coiling) or by microneurosurgery (clipping).

CONCLUSION

SAH is a life-threatening condition that requires immediate diagnosis, transfer to a neurovascular center, and treatment without delay.

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.

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.

Secular pattern of aneurismal rupture with the lunar cycle and season

Background The lunar cycle and seasons may be associated with rates of rupture of intracranial aneurysms, but the literature is mixed. Studies of the association between the lunar cycle and rates of aneurysm rupture used the eight qualitative moon phases. The purpose of this study was to assess any association of aneurysm rupture with the lunar cycle and with the season. Materials and methods We retrospectively reviewed all cases of subarachnoid haemorrhage secondary to ruptured intracranial aneurysm treated with endovascular coiling in our institution over a 10-year period. We included only cases with a known rupture date. We used the degree of illumination of the moon to quantitatively code the lunar cycle. Results A total of 212 cases were included in our analyses. The odds of aneurysm rupture were significantly greater ( p < 0.001) when the moon was least (new moon) and most (full moon) illuminated, as compared to the middle of the lunar cycle. The odds of rupture tended to be higher ( p = 0.059) in the summer, compared to autumn. Conclusions The odds of aneurysm rupture were greater when the moon was least illuminated (new moon) and most illuminated (full moon), compared to the middle of the lunar cycle.

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.

The association between weather conditions and stroke admissions in Turkey

Although several factors such as cigarette smoking, blood pressure, diabetes, obesity, hypercholesterolemia, physical inactivity and dietary factors have been well documented to increase the risk for stroke, there are conflicting data about the role of meteorological variables in the etiology of stroke. We conducted a retrospective study to investigate the association between weather patterns, including daily temperature, humidity, wind speed, and air pressure, and stroke admissions to the Emergency Department of Atatürk Training and Research Hospital in Ankara, Turkey, between January 2009 and April 2010. Generalized additive models with logistic link function were used to investigate the relationship between predictors and days with and without stroke admission at lags 0-4. A total of 373 stroke patients were admitted to the emergency department (ED) between January 2009 and April 2010. Of patients, 297 had ischemic stroke (IS), 34 hemorrhagic stroke (HS), and 42 subarachnoidal hemorrhage (SAH). Although we did not find any association between overall admissions due to stroke and meteorological parameters, univariable analysis indicated that there were significantly more SAH cases on days with lower daily mean temperatures of 8.79 ± 8.75 °C as compared to relatively mild days with higher temperatures (mean temperature = 11.89 ± 7.94 °C, p = 0.021). The multivariable analysis demonstrated that admissions due to SAH increased on days with lower daily mean temperatures for the same day (lag 0; odds ratio (OR) [95% confidence interval (95% CI)] = 0.93 [0.89-0.98], p = 0.004) and lag 1 (OR [95% CI] =0.76 [0.67-0.86], p = 0.001). Furthermore, the wind speed at both lag 1 (OR [95% CI] = 1.63 [1.27-2.09], p = 0.001) and lag 3 (OR [95% CI] = 1.43 [1.12-1.81], p = 0.004) increased admissions due to HS, respectively. In conclusion, our study demonstrated that there was an association between ED admissions due to SAH and HS and weather conditions suggesting that meteorological variables may, at least in part, play as risk factors for intracranial hemorrhages.

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 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.

Impact of the moon on cerebral aneurysm rupture

BACKGROUND

Several external and internal risk factors for cerebral aneurysm rupture have been identified to date. Recently, it has been reported that moon phases correlate with the incidence of aneurysmal subarachnoid hemorrhage (SAH), however, another author found no such association. Therefore, the present study investigates the influence of the lunar cycle on the incidence of aneurysmal rupture, the initial clinical presentation, and the amount of subarachnoid blood.

METHODS

Lunar phase and the particular day of the lunar cycle were correlated to the date of aneurysm rupture, aneurysm location, initial clinical presentation, and amount of subarachnoid blood assessed from CT scans of all patients treated for basal SAH in our department from 2003 to 2010.

RESULTS

We found no correlation between incidence of aneurysmal SAH, location of the aneurysm, initial clinical presentation, or amount of subarachnoid blood and the lunar cycle.

CONCLUSIONS

The moon influences neither the incidence of aneurysmal SAH nor the grade of initial neurological deterioration or amount of subarachnoid blood.

Seasonal variation in the incidence of aneurysmal subarachnoid hemorrhage associated with age and gender: 20-year results from the Yamaguchi cerebral aneurysm registry

BACKGROUND

This study was a cerebral aneurysm registry study conducted in a region with few climatic differences. Based on data collected for over 20 years, seasonal variations and characteristics of subarachnoid hemorrhage (SAH) due to ruptured aneurysms were analyzed.

METHODS

This study included 5,007 patients in the Yamaguchi Prefecture with aneurysmal SAH between 1986 and 2005. Incidence rates by month, sex, age, severity, and aneurysm site were analyzed.

RESULTS

In women, seasonal variation was observed, in particular among those aged ≥50 years. Among those aged 50-69 years, the highest incidence was in October, and the nadir was in June (peak-to-trough ratio = 1.72). At age ≥70 years, this was slightly different, with the highest incidence in December and the nadir in July (peak-to-trough ratio = 1.48). However, there was no seasonal variation in men overall; it was limited to elderly men at age ≥70 years, with the highest incidence in January and the nadir in July (peak-to-trough ratio = 2.9). Aneurysm site and severity showed no relationship with seasonal variation.

CONCLUSION

The present study shows seasonal variations in the onset of SAH. Seasonal variations in SAH differed depending on age and sex.

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.

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.

A temporal pattern in the occurrence of aneurysmal subarachnoid hemorrhage in the Province of Vojvodina, Serbia

BACKGROUND

Numerous studies with conflicting results have tried to prove the influence of seasonal variations or different meteorological factors on the occurrence of aneurysmal subarachnoidal hemorrhage (SAH). The aim of this study was to establish a mathematical model of a series of aneurysmal rupture dates in different patients and verify a temporal pattern in the occurrence of SAH.

METHODS

We analyzed a group of 563 patients with the exact aneurysm rupture dates, hospitalized at the Clinic of Neurosurgery, Clinical Center of Vojvodina, Novi Sad, Serbia, between January 1, 1998 and December 31, 2009. After the monthly distributions, we evaluated the period between two subsequent rupture dates.

RESULTS

The absolute number of SAH per month varied between 0 and 10. The monthly seasonal indices show a fluctuation of the time series (with the peak in March and nadir in September), but the median values of the number of aneurysm ruptures in a particular month did not differ significantly. The time scale of the aneurysm rupture dates shows that the most frequent interval between subsequent ruptures was 1 day (in 75 cases or 13.34%). Following this period, the number of days between ruptures showed a gradually decreasing pattern that could be approximated by exponential distribution.

CONCLUSIONS

The results are a clear confirmation that SAH patients do indeed present in clusters in a restricted population area. This exact clustering in our series is not particularly connected to month or season, yet strongly supports the existence of a temporal pattern in SAH occurrence.

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.