Subarachnoid haemorrhage occurrence exhibits a temporal pattern - evidence from meta-analysis

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.

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.

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

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

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 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.

Circadian Variation of Stroke Onset: A Hospital-Based Study

Aims and background.

The circadian pattern of stroke occurrence variation has been recognized with certain differences between authors and stroke types. The underlying reason may be related to exogenous factors (cyclic physical activity, including sleep–awake cycles and assuming the up-right posture) and endogenous factors, with their diurnal variation (blood pressure, hemostatic balance, autonomic system activity). The aims of the present study are to investigate the existence of a circadian variation of stroke and the possible differences between stroke subtypes in the Cluj Napoca area.

Materials and method.

The stroke event data were acquired from the Patient Records of a consecutive series of 1083 patients admitted through the Emergency Room at Neurology Departments I and II of the District Hospital of Cluj Napoca, between 1 January 2012 and 31 December 2012. The classifiable onset time was assigned to one of four six-hour intervals: 00.01–06.00 (night), 06.01–12.00 (morning), 12.01–18.00 (afternoon) and 18.01–24.00 (evening). Demographic data and vascular risk factors were recorded.

Results.

All three stroke types (ischemic stroke, hemorrhagic stroke and subarachnoid hemorrhage) have shown a circadian variation regarding their occurrence, with the peak of incidence in the morning and the nadir during nighttime. This circadian pattern is independent by demographic factors and vascular risk factors.

Conclusion.

Our study confirmed the circadian variation of onset occurrence for all stroke subtypes. Some triggering factors promote ischemic stroke and prevent hemorrhagic stroke. The diurnal pattern of variation with the higher incidence in the morning and the lower in the night may lead to chrono-therapeutic and preventive approach (chrono-therapy of the risk factors), which targets the period of the highest vulnerability after awaking.

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.

Incidence, national trend, and outcome of nontraumatic subarachnoid haemorrhage in Taiwan: initial lower mortality, poor long-term outcome

To investigate the longitudinal trend of nontraumatic subarachnoid haemorrhage (SAH), we analyzed the annual population-based incidence and mortality rate of nontraumatic subarachnoid hemorrhage in Taiwan. Logistic regression was used to identify independent predictors of mortality. The average incidence rate (IR) of nontraumatic SAH was 6.25 ± 0.88 per 100,000 per year. The prevalence of female patients was higher than in the male population (54.5% versus 45.5%). The average age of these patients was 55.78 ± 17.09 and females were older than males (58.50 ± 15.9 versus 52.45 ± 18.50, P < 0.001). Of these patients, 97.6% (611/626) were treated with surgical intervention with clipping procedure and 2.9% (18/626) with coiling. Total mortality of these patients was 13.4% (84/626). In adjusted analysis, age (odds ratio [OR], 0.97; 95% confidence interval [CI], 0.98-0.98; P < 0.001) and Charlson comorbidity index (OR, 0.709; 95% CI, 0.57-0.88; P = 0.002) remained independent predictors of the mortality. Patients with nontraumatic SAH had a much higher prevalence in older age groups and in females than in the general population. Patients with old age and more comorbidity have higher mortality. Aggressive management of patients might reduce the initial mortality; however, patient outcome still remains poor.

Increased incidence of aneurysmal subarachnoid hemorrhage on Sundays and Mondays in 1,862 patients from Eastern Finland

BACKGROUND

Temporal patterns of aneurysmal subarachnoid hemorrhage (aSAH) from saccular intracranial aneurysm (sIA) were studied in a consecutive series of 1,862 patients.

METHODS

Neurosurgery of Kuopio University Hospital (KUH) solely serves a defined catchment population in Eastern Finland. Kuopio's sIA database contains 1,596 sporadic and 266 familial patients admitted to KUH within 72 h from the onset of aSAH between 1980 and 2007. The distributions by the weekday of the onset of aSAH, admission to KUH, and occlusive therapy of the ruptured sIA were analyzed. Logistic regression was used to search for clinical variables (patients, sIA disease, clinical condition) that would independently correlate with each distribution.

RESULTS

The onset of aSAH occurred significantly most often (p < 0.001) on Sundays (n = 330) and Mondays (n = 309) and least frequently on Saturdays (n = 231). None of the clinical variables tested associated significantly and independently with the Sunday and Monday peaks. The admissions to KUH after aSAH were most frequent (p < 0.001) on Mondays (n = 331) and least frequent on Thursdays (n = 221) and Saturdays (n = 221). Overall, 1,655 patients underwent occlusive therapy, most frequently on Mondays (n = 318) and least frequently on Saturdays (n = 189) and Sundays (n = 197).

CONCLUSIONS

Sundays and Mondays were the most frequent and Saturdays the least frequent days of aSAH in a defined Eastern Finnish population. We could not identify any etiology to this temporal pattern. Binge drinking is frequent in Finland, especially among young males, but age and gender did not correlate with the Sunday and Monday peaks.

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.

Examining secular trends and seasonality in count data using dynamic generalized linear modelling: a new methodological approach illustrated with hospital discharge data on myocardial infarction

Time series of incidence counts often show secular trends and seasonal patterns. We present a model for incidence counts capable of handling a possible gradual change in growth rates and seasonal patterns, serial correlation, and overdispersion. The model resembles an ordinary time series regression model for Poisson counts. It differs in allowing the regression coefficients to vary gradually over time in a random fashion. During the 1983-1999 period, 17,989 incidents of acute myocardial infarction were recorded in the Hospital Discharge Registry for the county of North Jutland, Denmark. Records were updated daily. A dynamic model with a seasonal pattern and an approximately linear trend was fitted to the data, and diagnostic plots indicated a good model fit. The analysis conducted with the dynamic model revealed peaks coinciding with above-average influenza A activity. On average the dynamic model estimated a higher peak-to-trough ratio than traditional models, and showed gradual changes in seasonal patterns. Analyses conducted with this model provide insights not available from more traditional approaches.

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

Previous studies have suggested a possible association between meteorological factors and the onset of subarachnoid hemorrhage (SAH). We aimed to investigate the relationship between the onset of SAH and meteorological factors based on an hourly time-series analysis. We collected hourly data on transportation of patients with SAH using the ambulance records of the Tokyo Fire Department from January 1 to December 31, 2005. We also collected hourly meteorological data for Tokyo from the Japan Meteorological Agency during the same period. We performed a time-series analysis using the autoregressive integrated moving average (ARIMA) model to control for autocorrelations in the time-series data. There were 1729 patients with SAH (mean age 63.3 years; 60.2% women). We identified two circadian patterns in the onset of SAH: a daily peak at 10 am (p<0.001) and a seasonal peak in February (p<0.001). Based on the ARIMA time-series analysis, significant risk factors associated with the onset of SAH included: low temperature on the previous day (lag time 17h; p=0.005) and on the onset day (lag time 0h; p<0.001); high barometric pressure on the onset day (lag time 0h; p=0.001). Humidity was not associated with the onset of SAH. Among meteorological factors, low temperature and high barometric pressure may be risk factors for the onset of SAH.

Systematic review of reviews of risk factors for intracranial aneurysms

Systematic reviews of systematic reviews identify good quality reviews of earlier studies of medical conditions. This article describes a systematic review of systematic reviews performed to investigate factors that might influence the risk of rupture of an intracranial aneurysm. It exemplifies the technique of this type of research and reports the finding of a specific study. The annual incidence of subarachnoid haemorrhage resulting from the rupture of intracranial aneurysms is estimated to be nine per 100,000. A large proportion of people who have this bleed, will die or remain dependent on the care of others for some time. Reliable knowledge about the risks of subarachnoid haemorrhage in different populations will help in planning, screening and prevention strategies and in predicting the prognosis of individual patients. If the necessary data were available in the identified reviews, an estimate for the numerical relationship between a particular characteristic and the risk of subarachnoid haemorrhage was included in this report. The identification of eligible systematic reviews relied mainly on the two major bibliographic databases of the biomedical literature: PubMed and EMBASE. These were searched in 2006, using specially designed search strategies. Approximately 2,000 records were retrieved and each of these was checked carefully against the eligibility criteria for this systematic review. These criteria required that the report be a systematic review of studies assessing the risk of subarachnoid haemorrhage in patients known to have an unruptured intracranial aneurysm or of studies that had investigated the characteristics of people who experienced a subarachnoid haemorrhage without previously being known to have an unruptured aneurysm. Reports which included more than one systematic review were eligible and each of these reviews was potentially eligible. The quality of each systematic review was assessed. In this review, 16 separate reports were identified, including a total of 46 eligible systematic reviews. These brought together research studies for 24 different risk factors. This has shown that the following factors appear to be associated with a higher risk of subarachnoid haemorrhage: being a woman, older age, posterior circulation aneurysms, larger aneurysms, previous symptoms, "non-white" ethnicity, hypertension, low body mass index, smoking and alcohol consumption of more than 150 g per week. The following factors appear to be associated with a lower risk of subarachnoid haemorrhage: high cholesterol, diabetes and use of hormone replacement therapy.

Urbanization and stroke prevalence in Taiwan: analysis of a nationwide survey

This study aims to explore the prevalence of strokes among individuals and the association with urbanization levels. A total sample of 9,794 individuals was obtained from a nationwide survey on Taiwan for subsequent analysis in this study. After adjusting for gender, age, other risk factors for stroke and individual socioeconomic status, a multivariate logistic regression model was employed to investigate the relationships existing between the prevalence of strokes and the level of urbanization. This study finds that those living in areas at the highest level of urbanization (level 1) had the highest prevalence of strokes (2.49%). With decreasing urbanization level, there was a general decline in stroke prevalence. After adjusting for other factors, the multivariate logistic regression analyses showed that compared to participants living in the highest urbanization level, the respective odds ratios of suffering a stroke for those living in areas at the lowest levels of urbanization (levels 7 and 8), were 0.43 and 0.30. We conclude that after adjusting for other stroke risk factors, the level of urbanization is an important contributory factor to the overall prevalence of strokes in Taiwan.

Blood pressure, fatigue, and the pathogenesis of aneurysmal subarachnoid hemorrhage

BACKGROUND

Endovascular embolization and BP reduction appear to protect cerebral aneurysms from rupture, although they do not totally eliminate aneurysm wall stress as does surgical clipping. We investigate the possible mechanisms of rupture to offer an explanation for this.

METHODS

Fatigue modeling of cerebral aneurysms using BP as the source of wall stress loading and calculating the increase in cycles to failure produced by a reduction in stress loading.

RESULTS

A modest reduction in the stress loading of aneurysms leads to a disproportionately large increase in the time taken for them to rupture. This result is based on the following assumptions and is thus restricted to aneurysm for which they may reasonably be true. Fatigue is the dominant mode of failure. The final decline in strength is rapid. The aneurysm lasts at least 6 weeks before rupturing.

CONCLUSIONS

A slight reduction in the stress on aneurysm walls can dramatically reduce their risk of rupture.

Survival by time of day of hemodialysis: analysis of United States Renal Data System Dialysis Morbidity and Mortality Waves III/IV

BACKGROUND

Whether morning shift hemodialysis is associated with improved survival in comparison to patients receiving afternoon shift hemodialysis has not been shown for a representative sample of US chronic hemodialysis patients.

METHODS

We conducted a historical cohort study of a national database (US Renal Data System Dialysis Morbidity and Mortality Waves III/IV) of 6,939 patients who started hemodialysis therapy from January 1, 1990, through December 31, 1993. Patients were followed up through April 9, 2000, and censored at the time of change to a different modality, including transplantation. We estimated the adjusted hazard ratio for all-cause mortality based on the time of day of hemodialysis (0500 to 1200 for morning shift, 1200 to 1800 for afternoon shift, 1800 to midnight for evening shift). Cox regression analysis was used to adjust for other factors associated with survival.

RESULTS

For patients aged 60 years and older, the unadjusted 4-year survival rate for patients on morning shift hemodialysis was 28.8% versus 24.1% for patients on afternoon shift hemodialysis and 38.7% for patients on evening shift hemodialysis (P < 0.01 by log-rank test for both versus afternoon shift hemodialysis). Both morning shift (adjusted hazard ratio, 0.90; 95% confidence interval [CI], 0.83 to 0.98; P = 0.02) and evening shift hemodialysis (adjusted hazard ratio, 0.62; 95% CI, 0.48 to 0.80; P < or = 0.001) were independently associated with a lower risk for mortality compared with afternoon shift hemodialysis. No such differences were seen for patients younger than 60 years. Both morning shift and evening shift hemodialysis were independently associated with improved survival compared with afternoon shift hemodialysis in elderly chronic hemodialysis patients. No such association was found for younger patients.