Seasonal variation of cerebral hemorrhage in 236 consecutive cases in Brussels

Seasonal variation in the incidence of primary intracerebral hemorrhage: a 16-year nationwide analysis

Introduction

Data on nationwide trends and seasonal variations in the incidence of Intracerebral Hemorrhage (ICH) in the United States (US) are lacking.

Methods

We used the Nationwide Inpatient Sample (2004-2019) and Census Bureau data to calculate the quarterly (Q1:January-March; Q2:April-June; Q3:July-September; Q4:October-December) incidence rates (IR) of adult (≥18 years) ICH hospitalizations, aggregated across Q1-Q4 and Q2-Q3. We report adjusted incidence rate ratios (aIRR) and 95% confidence intervals (CI) for differences in the quarterly incidence of ICH, as compared to acute ischemic stroke (AIS), between Q1Q4 and Q2Q3 using a multivariable Poisson regression model. We additionally performed stratified analyses across the four US regions.

Results

Among 822,143 (49.0% female) ICH and 6,266,234 (51.9% female) AIS hospitalizations, the average quarterly crude IR of ICH was consistently higher in Q1Q4 compared to Q2Q3 (5.6 vs. 5.2 per 100,000) (aIRR, CI: 1.09, 1.08-1.11)-this pattern was similar across all four US regions. However, a similar variation pattern was not observed for AIS incidence. The incidence (aIRR, CI) of both ICH (1.01, 1.00-1.02) and AIS (1.03, 1.02-1.03) is rising.

Conclusion

Unlike AIS, ICH incidence is consistently higher in colder quarters, underscoring the need for evaluation and prevention of factors driving seasonal variations in ICH incidence.

Temporal patterns of suicide and circulatory system disease-related mortality are inversely correlated in several countries

BACKGROUND

Nearly 800,000 suicides occur worldwide annually and suicide rates are increasing faster than population growth. Unfortunately, the pathophysiology of suicide remains poorly understood, which has hindered suicide prevention efforts. However, mechanistic clues may be found by studying effects of seasonality on suicide and other mortality causes. Suicides tend to peak in spring-summer periods and nadir in fall-winter periods while circulatory system disease-related mortality tends to exhibit the opposite temporal trends. This study aimed to determine for the first time whether monthly temporal cross-correlations exist between suicide and circulatory system disease-related mortality at the population level. If so and if common biological factors moderate risks for both mortality types, such factors may be discoverable and utilized to improve suicide prevention.

METHODS

We conducted time series analyses of monthly mortality data from northern (England and Wales, South Korea, United States) and southern (Australia, Brazil) hemisphere countries during the period 2009-2018 (N = 41.8 million all-cause mortality cases). We used a Poisson regression variant of the standard cosinor model to determine peak months of mortality. We also estimated cross-correlations between monthly mortality counts from suicide and from circulatory system diseases.

RESULTS

Suicide and circulatory disease-related mortality temporal patterns were negatively correlated in Australia (- 0.32), Brazil (- 0.57), South Korea (- 0.32), and in the United States (- 0.66), but no temporal correlation was discernable in England and Wales.

CONCLUSIONS

The negative temporal cross-correlations between these mortality types we found in 4 of 5 countries studied suggest that seasonal factors broadly and inversely moderate risks for circulatory disease-related mortality and suicide, but not in all regions, indicating that the effect is not uniform. Since the seasonal factors of temperature and light exert opposite effects on suicide and circulatory disease-related mortality in several countries, we propose that physiologically-adaptive circulatory system responses to heat and light may increase risk for suicide and should be studied to determine whether they affect suicide risk. For example, heat and light increase production and release of the bioactive gas nitric oxide and reduce circulatory system disease by relaxing blood vessel tone, while elevated nitric oxide levels are associated with suicidal behavior, inverse effects that parallel the inverse temporal mortality patterns we detected.

The effect characteristics of temperature on stroke mortality in Inner Mongolia and globally

The current study investigated the correlation between stroke mortality and temperature. Monthly and seasonal variations in stroke mortality were plotted and daily stroke-related deaths were calculated. The lag times were calculated using the time series analysis. The correlation between stroke incidence and the diurnal temperature range (DTR) was analyzed using case-crossover analysis. Global stroke mortality was described in five latitudes. In the eastern region of Inner Mongolia, the stroke mortality was 174.18/105, about twice of that of the midwestern regions (87.07/105), and temperature was negatively correlated with stroke mortality. Mortality peaked in the winter and troughed in the summer (χ² = 13.634, P < 0.001). The days in which stroke-related deaths were greater than ten occurred between late October and early April. The effect of temperature on stroke incidence occurred during a lag time of 1 (P = 0.024) or 2 months (P = 0.039). A DTR over 13 °C was positively correlated (r = 0.95, P = 0.004) with stroke with a lag time of 1 day. The effect of temperature on stroke was shown to be the same for various populations. As the latitude increases, stroke mortality also increases with latitudes > 40°; the highest mortality was 188.05/105 at the highest latitude. Only in relatively cold regions as the temperature decreases does stroke mortality increase for various populations. Differences in the time lag as well as in the DTR lag and DTR critical point vary for both the temperature and region.

The Influence of Weather on the Incidence of Primary Spontaneous Intracerebral Hemorrhage

BACKGROUND

Intracerebral hemorrhage has been associated with changes in various weather conditions. The primary aim of this study was to examine the collective influence of temperature, barometric pressure, and dew point temperature on the incidence of primary spontaneous intracerebral hemorrhage (sICH).

METHODS

Between January 2013 and December 2016, patients with sICH due to hypertension or amyloid angiopathy with a known time of onset were identified prospectively. Meteorological variables 6 hours prior to time of onset were obtained from the National Oceanic Atmospheric Administration via two weather stations. Using a Monte-Carlo simulation, random populations of meteorological conditions in a 6-hour time window during the same years were generated. The actual meteorological conditions 6-hours prior to sICH were compared to those from the randomly generated populations. The false discovery rate method was used to identify significant meteorological variables.

RESULTS

Time of onset was identified in 455 of 603 (75.5%) patients. Distribution curves for change in temperature, mean barometric pressure, and change in barometric pressure 6-hours prior to hemorrhage ictus were found to be significantly different from the random populations. (FDR approach P < .05). For a given change in temperature associated with intracerebral hemorrhage, mean barometric pressure was higher (1018 millibar (mb) versus 1016 mb, P = .03). Barometric pressure data was not influenced by variations in temperature.

CONCLUSIONS

We concluded that barometric pressure primarily influences the incidence of intracerebral hemorrhage. The association described in the literature between temperature and intracerebral hemorrhage is likely confounded by variations in barometric pressure.

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

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

Changes in extreme events and the potential impacts on human health

Extreme weather and climate-related events affect human health by causing death, injury, and illness, as well as having large socioeconomic impacts. Climate change has caused changes in extreme event frequency, intensity, and geographic distribution, and will continue to be a driver for change in the future. Some of these events include heat waves, droughts, wildfires, dust storms, flooding rains, coastal flooding, storm surges, and hurricanes. The pathways connecting extreme events to health outcomes and economic losses can be diverse and complex. The difficulty in predicting these relationships comes from the local societal and environmental factors that affect disease burden. More information is needed about the impacts of climate change on public health and economies to effectively plan for and adapt to climate change. This paper describes some of the ways extreme events are changing and provides examples of the potential impacts on human health and infrastructure. It also identifies key research gaps to be addressed to improve the resilience of public health to extreme events in the future.

IMPLICATIONS

Extreme weather and climate events affect human health by causing death, injury, and illness, as well as having large socioeconomic impacts. Climate change has caused changes in extreme event frequency, intensity, and geographic distribution, and will continue to be a driver for change in the future. Some of these events include heat waves, droughts, wildfires, flooding rains, coastal flooding, surges, and hurricanes. The pathways connecting extreme events to health outcomes and economic losses can be diverse and complex. The difficulty in predicting these relationships comes from the local societal and environmental factors that affect disease burden.

Seasonal Variations in Neurological Severity and Outcomes of Ischemic Stroke - 5-Year Single-Center Observational Study

BACKGROUND

Seasonal variations in the severity and outcomes of stroke remain unclarified.Methods and Results:A total of 2,965 acute ischemic stroke patients from a single-center prospective registry were studied. Among the total patients, stroke onset did not vary by season, though it varied with a peak in winter when limited to patients >75 years old (P=0.026), when limited to patients with moderate-to-severe initial neurological deficits (National Institutes of Health Stroke Scale Score ≥10, P=0.014), and when limited to those with cardioembolic stroke (n=1,031, P=0.010). In 1,934 patients with noncardioembolic stroke, stroke onset did not vary by season. After multivariable adjustment, moderate-to-severe neurological deficits were more common in winter (odds ratio 1.37, 95% confidence interval 1.10-1.72) and spring (1.27, 1.01-1.60), and death at 1 year was more common in summer than in fall (1.55, 1.03-2.36); death or dependency (modified Rankin Scale score 3-6) and death or bedridden (score of 5-6) were not differently common among the seasons.

CONCLUSIONS

Overall ischemic stroke showed a fairly even distribution among the 4 seasons. Cardioembolic stroke was more common in winter. Ischemic stroke patients had more moderate-to-severe initial neurological deficits in winter and spring. Poor clinical outcomes at 1 year were generally similar among the seasons. Ischemic stroke is not necessarily a winter-dominant disease.

Revealing the association between cerebrovascular accidents and ambient temperature: a meta-analysis

The association between cerebrovascular accidents (CVA) and weather has been described across several studies showing multiple conflicting results. In this paper, we aim to conduct a meta-analysis to further clarify this association, as well as to find the potential sources of heterogeneity. PubMed, EMBASE, and Google Scholar were searched from inception through 2015, for articles analyzing the correlation between the incidence of CVA and temperature. A pooled effect size (ES) was estimated using random effects model and expressed as absolute values. Subgroup analyses by type of CVA were also performed. Heterogeneity and influence of covariates-including geographic latitude of the study site, male percentage, average temperature, and time interval-were assessed by meta-regression analysis. Twenty-six articles underwent full data extraction and scoring. A total of 19,736 subjects with CVA from 12 different countries were included and grouped as ischemic strokes (IS; n = 14,199), intracerebral hemorrhages (ICH; n = 3798), and subarachnoid hemorrhages (SAH; n = 1739). Lower ambient temperature was significantly associated with increase in incidence of overall CVA when using unadjusted (pooled ES = 0.23, P < 0.001) and adjusted data (pooled ES = 0.03, P = 0.003). Subgroup analyses showed that lower temperature has higher impact on the incidence of ICH (pooled ES = 0.34, P < 0.001), than that of IS (pooled ES = 0.22, P < 0.001) and SAH (pooled ES = 0.11, P = 0.012). In meta-regression analysis, the geographic latitude of the study site was the most influencing factor on this association (Z-score = 8.68). Synthesis of the existing data provides evidence supporting that a lower ambient temperature increases the incidence of CVA. Further population-based studies conducted at negative latitudes are needed to clarify the influence of this factor.

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.

A Community-Based Study of the Correlation of Hemorrhagic Stroke Occurrence with Meteorologic Factors

BACKGROUND

Meteorologic variations may affect hemorrhagic stroke. Thus, the aim of this study was to explore the correlation of daily meteorologic factors with increased incidence of hypertensive intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH) in a community-based study.

METHODS

In a span of 2 years, 735 patients suffering from hypertensive ICH or SAH were enrolled in the study in Fularji District, Heilongjiang Province, China. Daily meteorologic data were obtained from the Bureau of Meteorology of Qiqihar. Daily meteorologic parameters with and without events were compared with hypertensive ICH and SAH, respectively. Logistic regression was used to assess the correlation of meteorologic factors with hypertensive ICH and SAH.

RESULTS

Daily mean ambient temperature (AT) was statistically associated with the onset of primary hypertensive ICH (odds ratio [OR], .983; P < .001) and SAH (OR, .984; P = .046). After adjustment with AT variations, the occurrence of primary hypertensive ICH was not only influenced by daily mean AT (P = .0004) but also by the interaction between the mean temperature and its variation (P = .0082). Interestingly, there was no statistical association between meteorologic factors and recurrent hypertensive ICH.

CONCLUSIONS

The higher incidence of primary hypertensive ICH in the late spring and early autumn was because of the influence of daily mean AT and its variation. When temperature changed, suddenly dropping in the hot weather or rising in the cold weather, the incidence of primary hypertensive ICH was also increased. Conversely, the incidence of SAH increased during days with lower temperature.

"Timing" of arrival and in-hospital mortality in a cohort of patients under anticoagulant therapy presenting to the emergency departments with cerebral hemorrhage: A multicenter chronobiological study in Italy

Therapy with oral anticoagulants (OACs) is a risk factor for cerebral hemorrhage (CH). Although different studies have been undertaken to investigate the timing of the onset of major cardiovascular events, no data exist on temporal patterns of the onset of CH in subjects treated with OACs. The aim of this study is to evaluate the timing of CH in patients treated with OACs. All patients who developed CH under OACs therapy and admitted to 28 Italian Emergency Departments (EDs) between September 2011 and July 2013 were enrolled. Age, sex, time and location of the hemorrhagic lesion, type of the bleeding events (idiopathic or post-traumatic), anticoagulant therapy (warfarin or new oral anticoagulants - NOAs) and time of ED admission (i.e., hour, day, month and season) were recorded. Five hundred and seventeen patients (63.2% male aged 80 ± 7.9 yrs) with CH were involved. Warfarin was taken by 494 patients (95.6%), and NOAs by 23 (4.4%). In-hospital mortality (IHM) was recorded in 208 cases (40.2%). Cosinor analysis showed a peak of CH arrival between 12:00 and 14:00 h both in the whole population (PR 73.9%, p = 0.002) and the male subgroup (PR 65.2%, p = 0.009), whereas females showed an anticipated morning peak between 08:00 and 10:00 h (PR 65.7%, p = 0.008). A further analysis between idiopathic and post-traumatic CH confirmed the presence of a 24 h pattern with a peak between 12:00 and 14:00 h (PR 58.5%, p = 0.019) and between 08:00 and 10:00 h (PR80.1%, p < 0.001) for idiopathic events and post-traumatic hemorrhages, respectively. Moreover, a seasonal winter peak was identified for idiopathic forms (PR 74%, p = 0.035), and a summer peak for post-traumatic forms (PR 77%, p = 0.025). The present study suggests the presence of a temporal pattern of ED arrivals in CH patients treated with OACs.

Higher ratio of ischemic stroke to hemorrhagic stroke in summer

BACKGROUND

The aim of this study was to investigate the seasonal variation of the ratio of hemorrhagic stroke to ischemic stroke. The working hypothesis is that the ratio may vary among seasons.

METHODS

A total of 13,788 patients registered in the Kyoto Stroke Registry from 1999 to 2009 were divided into 4 groups based on the season in which stroke developed. We calculated odds ratio (OR) for the incidence of stroke as a whole, cerebral infarction (CeI), cerebral hemorrhage (CH), and subarachnoid hemorrhage (SAH) in spring, autumn, and winter setting summer as a reference. Using a logistic regression, we evaluated the seasonal variation of ORs for CH/CeI and for SAH/CeI with adjustment for age, gender, and risk factors.

RESULTS

Incidence of CeI in autumn was lower than in summer (OR: 0.93; 0.87-0.98, P = 0.013). Incidence of CH was higher in spring (OR: 1.36; 1.23-1.49, P < 0.001), in autumn (OR: 1.16; 1.05-1.28, P = 0.004), and in winter (OR: 1.37; 1.25-1.51, P < 0.001) than in summer. Incidence of SAH was higher in spring (OR: 1.51; 1.28-1.79, P < 0.001) and in winter (OR: 1.44; 1.22-1.70, P < 0.001) than in summer. OR for CH/CeI in spring, autumn, and winter were 1.28 (1.13-1.45, P < 0.001), 1.26 (1.11-1.43, P < 0.001), and 1.35 (1.19-1.53, P < 0.001), respectively. ORs for SAH/CeI were 1.46 (1.19-1.79, P < 0.001), 1.34 (1.09-1.66, P = 0.007), and 1.50 (1.22-1.84, P < 0.001), respectively.

CONCLUSIONS

Seasonal variations differed among stroke subtypes. The OR for CH/CeI and for SAH/CeI was lower in summer and higher in the rest of seasons independent of age, gender, and risk factors.

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.

Association between the daily temperature range and occurrence of spontaneous intracerebral hemorrhage

OBJECTIVE

We have observed, anecdotally, that the incidence of primary spontaneous intracerebral hemorrhage (sICH), as well as spontaneous subarachnoid hemorrhage, varies in accordance with seasonality and meteorological conditions. This retrospective single-hospital-based study aimed to determine the seasonality of sICH and the associations, if any, between the occurrence of sICH and meteorological parameters in Incheon city, which is a northwestern area of South Korea.

METHODS

Electronic hospital data on 708 consecutive patients admitted with primary sICH from January 2008 to December 2010 was reviewed. Traumatic and various secondary forms of ICHs were excluded. Average monthly admission numbers of sICH were analyzed, in relation with the local temperature, atmospheric pressure, humidity, and daily temperature range data. The relationships between the daily values of each parameter and daily admission numbers of sICH were investigated using a combination of correlation and time-series analyses.

RESULTS

No seasonal trend was observed in sICH-related admissions during the study period. Furthermore, no statistically significant correlation was detected between the daily sICH admission numbers and the meteorological parameters of temperature, atmospheric pressure and humidity. The daily temperature range tended to correlate with the number of daily sICH-related admissions (p = 0.097).

CONCLUSION

This study represents a comprehensive investigation of the association between various meteorological parameters and occurrence of spontaneous ICH. The results suggest that the daily temperature range may influence the risk of sICH.

Winter cardiovascular diseases phenomenon

This paper review seasonal patterns across twelve cardiovascular diseases: Deep venous thrombosis, pulmonary embolism, aortic dissection and rupture, stroke, intracerebral hemorrhage, hypertension, heart failure, angina pectoris, myocardial infarction, sudden cardiac death, venricular arrythmia and atrial fibrillation, and discuss a possible cause of the occurrence of these diseases. There is a clear seasonal trend of cardiovascular diseases, with the highest incidence occurring during the colder winter months, which have been described in many countries. This phenomenon likely contributes to the numbers of deaths occurring in winter. The implications of this finding are important for testing the relative importance of the proposed mechanisms. Understanding the influence of season and other factors is essential when seeking to implement effective public health measures.

Seasonal variation in spontaneous intracerebral hemorrhage frequency in Chengdu, China, is independent of conventional risk factors

Seasonal variations in the incidence of intracerebral hemorrhage (ICH) have been extensively evaluated in studies conducted in various parts of the world. However, seasonal variation of ICH in China has not been comprehensively reported in the English literature. The aim of the present study was to examine the seasonal variation of spontaneous ICH incidence and the 28-day case-fatality rate in a Chinese population. We also examined whether this variation was modified by conventional stroke risk factors (hypertension, diabetes mellitus, smoking, drinking alcohol). From 2006 to 2009, 1615 hemorrhagic stroke events (male, 965; female, 650) were registered in residents of the Jinjiang and Wuhou districts, Chengdu, China. Seasonal variation was calculated for the whole period. Incidence rates (per 100,000 person-seasons) and 95% confidence intervals (CI) were calculated by gender and age for winter, spring, summer, and autumn. After stratifying patients by their risk factor history, odds ratios and 95% CI of having a stroke in autumn, winter, and spring were calculated, with summer serving as a reference. Among the seasons, the incidence per 100,000 person-years of spontaneous cerebral hemorrhage was highest in the winter (45.5, 95% CI, 38.4-52.7) and lowest in summer (24.1, 95% CI, 21.9-26.2). Winter incidence was highest in both men and women, and in subjects younger than 60years as well as subjects 60years or older. The winter excess in stroke incidence was observed regardless of the presence or absence of risk factors. Factors that explain this excess need further investigation.

Environmental factors and stroke: A selective review

Despite numerous prior stroke risk factor investigations, much remains unknown about the effect of environmental factor changes on stroke incidence and mortality rates. Yet these data might be important for defining a number of measures to prevent stroke and for developing a greater understanding of the origin and incidence trends of stroke in different regions and populations. In this paper we review the current state of knowledge about certain environmental stroke risk factors.

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.

Ambient temperature and spontaneous intracerebral haemorrhage: a cross-sectional analysis in Tainan, Taiwan

OBJECTIVES

Ambient temperature has been reported to play a role in the occurrence of spontaneous intracerebral haemorrhage (ICH). This study aimed to investigate the relation between ambient temperature of onset time and ICH and the effect of hourly temperature within 72 h before ICH.

DESIGN

This is a cross-sectional case-only study and a retrospective analysis of a prospective database.

SETTING

Two medical centres in Southern Taiwan participating a prospective stroke registry.

PARTICIPANTS

A total of 933 patients with ICH registered from August 2006 to July 2008.

PRIMARY AND SECONDARY OUTCOME MEASURES

The hourly temperature was collected, and patients were grouped according to the deciles of hourly temperature at onset. Primary outcome was the association between the number of ICH cases and mean temperature (or temperature variation). Secondary outcome was the difference of onset temperature and hourly temperature before onset in patients with known onset time.

RESULTS

Winter (n=282) had significant higher ICH cases than other seasons (n=651; p=0.002). Of those patients with an exact time of onset, the results showed 13% patients occurred at the lowest decile temperature group (<17.4°C) and 8% patients occurred at the highest decile temperature group (>30.8°C). It showed a significant temperature change before onset for these patients (p<0.005).

CONCLUSIONS

This study showed that lower ambient temperature and variation of temperatures precipitated ICH in southern Taiwan. Better protecting vulnerable people from cold temperatures may prevent the occurrences of ICH.

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.

Preventing cold-related morbidity and mortality in a changing climate

Winter weather patterns are anticipated to become more variable with increasing average global temperatures. Research shows that excess morbidity and mortality occurs during cold weather periods. We critically reviewed evidence relating temperature variability, health outcomes, and adaptation strategies to cold weather. Health outcomes included cardiovascular-, respiratory-, cerebrovascular-, and all-cause morbidity and mortality. Individual and contextual risk factors were assessed to highlight associations between individual- and neighborhood-level characteristics that contribute to a person's vulnerability to variability in cold weather events. Epidemiologic studies indicate that the populations most vulnerable to variations in cold winter weather are the elderly, rural and, generally, populations living in moderate winter climates. Fortunately, cold-related morbidity and mortality are preventable and strategies exist for protecting populations from these adverse health outcomes. We present a range of adaptation strategies that can be implemented at the individual, building, and neighborhood level to protect vulnerable populations from cold-related morbidity and mortality. The existing research justifies the need for increased outreach to individuals and communities for education on protective adaptations in cold weather. We propose that future climate change adaptation research couple building energy and thermal comfort models with epidemiological data to evaluate and quantify the impacts of adaptation strategies.

Hospitalizations due to spontaneous intracerebral hemorrhage in the region of Nis (Serbia): 11-year time-series analysis

BACKGROUND

The study of seasonal variability of intracerebral hemorrhage (ICH) occurrence may contribute to a better understanding of the nature of this disease and open up new perspectives in its prevention. The aim of this study was to test seasonal patterns in the number of admissions of ICH patients and determine which months have maximal and minimal number of admissions.

METHODS

The main data source for this study was a hospital-based registry at the Clinic of Neurology in Nis, Serbia. During the studied period (1997-2007) a total of 1569 ICH patients were registered. Time series, consisting of the monthly number of hospitalized patients, for the 128 months of the study duration, has been successfully modeled using the multiplicative Auto Regressive Integrated Moving Average (ARIMA) model.

RESULTS

Using the maximum likelihood method, utilizing Melrad's algorithm, the parameters of this ARIMA model have been calculated: constant (estimate 12.068, p<0.001), auto regressive-AR(1) (estimate 0.866, p<0.001), moving average-MA(1) (estimate 0.775, p<0.001), seasonal moving average-SMA(12) (estimate -0.198, p=0.036). ARIMA modeling has been successful and showed that there is a clear seasonal pattern in the data analyzed.

CONCLUSION

Based on the seasonal multiplicative ARIMA model and the seasonal time series decomposition, we showed that, in the period covered by the study, the peak of admissions occurred in March, and the trough of admissions was found in August.

Intracerebral hemorrhage and meteorological factors in Chongqing, in the southwest of China

Studies have reported the relationship between intracerebral hemorrhage (ICH) and meteorological factors. However, few of those study analyses were dependent on daily meteorological factors. The aim of this study is to evaluate the relationship between various meteorological data and ICH cases from Chongqing, in the southwest of China. One thousand nineteen intracerebral hemorrhage events registered in our hospital were recorded from 1 January 2006 to 30 August 2009. Meteorological parameters were analyzed, including season, month, air temperature, humidity, atmospheric pressure, visibility, presence of fog, and wind velocity. The chi-square test for goodness of fit was used for statistical evaluations. Significant differences in seasonal and monthly patterns of ICH onset were observed. The incidence of ICH attack was highest in winter and lowest in summer (p<0.0001). The monthly variation was consistent with the above pattern (p=0.002). Daily air temperature (p<0.0001), humidity (p=0.002), and atmospheric pressure (p<0.0001) were associated with the admission rate. However, no significant relationships were found between visibility (p=0.62), presence of fog (p=0.32), or wind velocity (P=0.5) and the risk of ICH. Our study demonstrates that the incidence of ICH is closely related to some meteorological factors, such as season, daily air temperature, humidity, and atmospheric pressure.

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.

Timing pattern of onset in hypertensive intracerebral hemorrhage patients

The temporal pattern of onset of hypertensive intracerebral hemorrhage (ICH) has been evaluated in previous reports, but there are few published data on this pattern in Chongqing, China. The purpose of this study is to explore the temporal pattern of diurnal, weekly and monthly variations in the onset of hypertensive ICH from a hospital-based population. The study retrospectively reviewed 230 residents who suffered from hypertensive ICH between January 2008 and August 2009 in our hospital. The temporal pattern was investigated by hours, days and months. Chi-square test for goodness of fit was used for statistical analysis. Significant differences of the onset time of hypertensive ICH patients could be seen in diurnal variation (p=0.000) and in monthly variation (p=0.000), but could not be found in weekly variation (p=0.466). There was a bimodal distribution in diurnal variation, and monthly variation showed that the occurrence of hypertensive ICH mainly focuses on the period from December to May. Our study demonstrated the existence of diurnal and monthly variations and no significant weekly variation can be found in the time of onset of hypertensive ICH.

Prediction of the incidence of spontaneous intracerebral hemorrhage from meteorological data

We analyzed the relationship between the incidence of spontaneous intracerebral hemorrhage (ICH) and various meteorological data (daily atmospheric air pressure, air temperature, precipitation, humidity, presence of typhoons, occurrence of the rainy season, wind velocity, and wind direction) for patients at Teraoka Memorial Hospital in Shin-ichi Town, Japan, from January 1, 2001 to December 31, 2003. All data were analyzed by contingency table analysis and multivariate regression analysis. From January 1, 2002 to December 31, 2003, we identified high-risk ICH days as those days for which the preceding 3 days mean recorded air pressure of 1,015 hPa or more and then conducted a statistical comparison of the incidence of ICH on high-risk ICH days with that on the other days. Our subjects were 164 patients with ICH. The relative risk of high-risk ICH days is 1.46 (Fisher's exact test, p=0.04). Mann-Whitney's U-tests indicate ICH tends to occur on days with lower maximum air temperature. Multivariate logistic regression analysis revealed that 3 incidences influence the occurrence of intracerebral hemorrhage (p<0.01 each): (1) days associated with 4-day periods of mean air pressure in excess of 1,015 hPa; (2) days during which a typhoon was approaching; and (3) days with west or southwest wind . Detailed examination of meteorological data indicates a relationship with the incident rate of ICH.

Relationship between the occurrence of spontaneous intracerebral hemorrhage and holidays and traditionally unlucky days in Fukuyama City, Hiroshima Prefecture, Japan

To investigate whether calendrical information influences the occurrence of spontaneous intracerebral hemorrhage, we statistically compared the incidence of intracerebral hemorrhage for inpatients at Teraoka Memorial Hospital (164 patients), against various calendrical factors such as the day of the week, national holidays, and RokuYo (a recurring six-day series of lucky and unlucky days in the Japanese traditional calendar) over the period from January 1, 2001 to December 31, 2003. On Japanese national holidays the relative risk of intracerebral hemorrhage is significantly higher than on other days, certainly due to much more alcohol consumption on holidays. During RokuYo, the relative risk of intracerebral hemorrhage is extremely low on the traditionally unlucky days of ButsuMetsu and TomoBiki, as many Japanese people restrain their activities on these days. Certain days of the year and certain times of the Japanese supplemental calendars correlate significantly with the incidence of intracerebral hemorrhage.

Meteorological factors and the onset of hypertensive intracerebral hemorrhage

There have been numerous studies of the relationship between intracerebral hemorrhage (ICH) and meteorological conditions, but their conclusions have been inconsistent. Poor discrimination of ICH subtypes (primary or secondary) may have obscured the conclusions. Although most studies have analyzed seasonal or monthly variation, daily meteorological data are more appropriate for determining whether weather conditions play a role in triggering the onset of ICH. No studies have examined the activity and location of patients at the time of onset. The aim of this study was to evaluate the relationship between the occurrence of hypertensive ICH and daily meteorological parameters, in addition to examining the effect of the location and activity of the patient at the time of onset. We analyzed 138 patients with severe hypertensive ICH in a hospital-based population. We assessed whether daily meteorological parameters for the days on which ICH occurred differed from the days without ICH onset. Days on which hypertensive ICH occurred had a significantly lower minimum temperature and a decreased minimum temperature from that of the previous day ( P=0.042 [corrected] and 0.012 [corrected] respectively). There were no significant differences among subgroups of patients categorized according to their location and activity at the time of onset for any of the meteorological parameters.

Variation saisonnière des accidents vasculaires cérébraux et influence des conditions météorologiques

The aim of this paper was to study the seasonal and Monthly distribution of different subtypes of strokes, and also the influence of the most usual meteorological factors on their incidence. The study, based on the population-based data of the Dijon register of stroke (France), involved 3287 patients with a cerebrovascular event during the Years 1985-1998. The seasonal distribution pointed out a summer decrease for all stroke subtypes. The cerebrovascular risk was the highest in autumn for small artery atheroma infarcts and for cerebral infarcts and, among these later, for cardioembolic infarcts and large artery atheroma infarcts, as well as for subarachnoid hemorrhages and for the total number of strokes. It was followed by spring (total number of strokes, small artery atheroma infarcts, cerebral infarcts) and/or winter (subarachnoid hemorrhages, cerebral infarcts, cardioembolic infarcts and large artery atheroma infarcts). For intracerebral hemorrhages, the risk peaked in spring and secondly in autumn. But the difference from one season to another was significant only for total number of strokes, cerebral infarcts and, among the later, for cardioembolic infarcts and large artery atheroma infarcts. As regards the Monthly distribution, the difference between Months was significant only for the total number of strokes and cerebral infarcts, with a minimum from July to September and a maximum in October for the later. Correlations with meteorological data were found for the total number of strokes, cerebral infarcts, cardioembolic infarcts, large artery atheroma infarcts and small artery atheroma infarcts. They showed an influence of temperature and relative humidity of the day of stroke or of the one to five days before. Correlations with wind speed, duration of sunshine or snow, even if less frequent, could also be found. Such results sometimes differ from those of some earlier studies, for which the climate and the risk factors were not the same, showing that regional epidemiological studies are necessary in order to determine the relations between seasons, meteorological factors and strokes.

Diurnal and seasonal variations in the onset of primary intracerebral hemorrhage in individuals living in Izumo City, Japan

OBJECT

Little is known about the temporal patterns of primary intracerebral hemorrhage (ICH) among the general population. The aim of this study was to examine diurnal and seasonal variations in the onset of ICH in a community-based series.

METHODS

The study population consisted of 350 patients who presented with primary ICH for the first time and were treated between 1991 and 1998 in Izumo City, Japan. Among the entire patient population, the onset of hemorrhage was rarely observed during the night and a peak was observed in the late afternoon. In men 69 years of age or younger, the onset of ICH exhibited a bimodal distribution, with an initial high peak between 8:00 and 10:00 a.m. and a second, lower peak between 6:00 and 8:00 p.m. In contrast, in men 70 years of age or older and in women regardless of age, only a single evening peak, between approximately 6:00 and 10:00 p.m., was found, and no morning peak was observed. For the entire patient population (for both sexes), and for men alone, seasonal variations--a peak in winter and a trough in summer-were significant for all age groups combined. This factor was significant for patients 69 years of age or younger, during the daytime hours (8:00 a.m.-8:00 p.m.), and for patients with untreated hypertension; however, it was not significant for patients 70 years of age or older, during nighttime hours (10:00 p.m.-8:00 a.m.), or for treated hypertensive and normotensive patients. In women, no significant seasonal patterns were found, regardless of patient age, time of day at onset of ICH, or the presence of risk factors. Seasonal variations were statistically significant for patients with hematomas larger than 5 ml, but not for those with hematomas 5 ml or smaller.

CONCLUSIONS

Temporal distributions in the onset of ICH seem to be influenced by patient sex and age. The seasonal patterns of ICH occurrence may result mainly from changes that occur during the daytime, and may also be modified by the presence of untreated hypertension and by the volume of the hematoma.

Seasonal variation in the incidence of aneurysmal subarachnoid hemorrhage in hospital- and community-based studies

OBJECT

The aim of this study was to examine seasonal variations in the onset of aneurysmal subarachnoid hemorrhage (SAH) in one hospital-based and one community-based patient series.

METHODS

The study population consisted of 941 patients with aneurysmal SAH who were admitted to Shimane Prefectural Central Hospital and 358 patients who were treated in Izumo City, Japan. When investigated as a whole, no significant seasonal variations were found in either population; however, in both series, statistically significant seasonal trends, with a peak in winter and a nadir in summer, were found among patients aged 59 years or younger (p < 0.05 for the hospital-based series and p < 0.005 for the community-based series), but not among those aged 60 years or older, regardless of sex. In the hospital-based series, seasonal variations were most apparent at certain times of day, with significant variations observed between 8:00 a.m. and 10:00 a.m. or 8:00 a.m. and noon (p < 0.001 and p < 0.005, respectively), regardless of patient age, and between 4:00 p.m. and 6:00 p.m. for patients aged 59 years or younger (p < 0.05). Consequently, seasonal variations were significant during daytime hours (between 8:00 a.m. and 8:00 p.m., p < 0.005) but not during the night (between 8:00 p.m. and 8:00 a.m.). Similar tendencies were found in the community-based series. Among patients aged 59 years or younger who had no risk factors for SAH, these seasonal variations were significant in both series. In patients with untreated hypertension, who were current smokers and daily alcohol drinkers, however, no significant patterns were observed in either series, even among younger patients.

CONCLUSIONS

In both hospital- and community-based studies, aneurysmal SAH appears to undergo seasonal variation, with a peak in winter and a nadir in summer. This seasonal pattern may be derived mainly from the occurrence of SAH in the morning, but may also be modified by patient age and SAH risk factors, resulting in the masking of significant seasonal patterns when all patients are considered together.

Relationship of aneurysmal subarachnoid hemorrhage to changes in atmospheric pressure: results of a prospective study

OBJECT

The purpose of this study was to evaluate the relationship between atmospheric pressure and subarachnoid hemorrhage (SAH) in a region in the English Midlands.

METHODS

All patients with angiographically proven SAH for the calendar year 1998 were analyzed. A geographical allocation was made based on the patients' origin within the region. The events were then compared with the data available for the local atmospheric pressures. One hundred nine patients had an SAH during the time period studied. The median atmospheric pressure recorded was 1014.5 millibars. Atmospheric pressure was modestly correlated with the number of SAHs per day (Spearman's rank correlation, r = 0.33; p < 0.0001); the daily change in atmospheric pressure also correlated mildly (r = 0.34, p < 0.0001). No other statistically significant association was found.

CONCLUSIONS

The authors have shown a relationship between high atmospheric pressure and increased incidence of SAH. The underlying reason for this remains obscure.

Primary intracerebral and aneurysmal subarachnoid hemorrhage in Izumo City, Japan. Part I: incidence and seasonal and diurnal variations

OBJECT

The purpose of this community-based study was first to estimate the incidence rates of primary intracerebral hemorrhage (ICH) and aneurysmal subarachnoid hemorrhage (SAH) in Izumo City, Japan, and second to investigate whether there were seasonal and diurnal periodicities in their onset.

METHODS

During 1991 through 1996, 267 patients with primary ICH and 123 with aneurysmal SAH were treated in Izumo City. The crude and the age- and sex-adjusted annual incidence rates per 100,000 population for all ages were 52 and 48 for ICH and 24 and 23 for SAH, respectively. These incidence rates were higher than those previously published for any other geographical region. The incidence rates of both ICH and SAH increased almost linearly with age. For ICH, a significant seasonal pattern was observed in men and in patients younger than 65 years, with a peak in winter and a trough in summer. However, no significant seasonal fluctuation was found in women or in individuals aged 65 years or older. There was no significant seasonal periodicity for SAH, even when patients were analyzed according to sex and age. Diurnal variations in the onset of both ICH and SAH were significant (except in men with SAH), with a nadir between midnight and 6:00 a.m.

CONCLUSIONS

The actual incidence rates of both primary ICH and aneurysmal SAH seem to be much higher than have been reported so far. In addition, the data indicate the existence of seasonal periodicity for men and younger patients with ICH, and that the risk of both ICH and SAH is lower during nighttime.

Seasonal variation of blood cholesterol levels: study methodology

This manuscript provides a description of the methodology used in the Seasonal Variation of Blood Cholesterol Levels (SEASON) study, with the intent of informing the scientific community of the available data sets and to invite a dialogue with scientists in complementary fields. The primary aim of the SEASON study is to describe and delineate the causes of seasonal variation of blood lipid levels in the general population. This research project is designed specifically to systematically collect and analyze a number of important variables necessary to study the role of seasonality in blood lipids and relevant covariates.

Seasonal variation in the occurrence of ischemic stroke and subarachnoid hemorrhage in Siberia, Russia. A population-based study

Epidemiological studies on the relationship between stroke occurrence and the seasons in different countries produced inconsistent results and little is known about these associations in a general population. We report a population-based study of 214 patients with first-ever ischemic stroke (IS, data for 1992) and 64 patients with first-ever subarachnoid hemorrhage (SAH) registered in the 25-74 years old population of Oktiabrsky District of Novosibirsk, Russia in 1982-92. IS and SAH incidence in four seasons (winter, spring, summer, autumn) was evaluated by means of a chi-square test. Poisson regression analysis was used to compute the rate ratios (RRs) and corresponding confidence intervals (CIs) for the occurrence of IS and SAH in winter, spring, and autumn compared with summer. Seasonal variations in the occurrence of IS were significant for the group of young men (25-64 years) and the group of older women (65-74 years) only. The age and sex adjusted RR of the occurrence of IS in winter was 49% greater than in summer (95%CI 1-119%). When men and women were analyzed separately and the rates were adjusted for age, a significantly higher risk of IS was found only in men (RR = 2.48; 95% CI 1.27-4.83) in spring compared with summer. No seasonality was observed for the occurrence of SAH in both men and women. Our findings indicate that there is a significantly greater incidence of ischemic stroke during winter in Siberia, Russia, whereas the incidence of SAH does not show a seasonal variation.

Chronobiological patterns of onset of acute cerebrovascular diseases

There is a considerable amount of data indicating that several major unfavorable cerebrovascular events are not randomly distributed over time, but show a peculiar distribution along the day, the week, and the months of the year. The authors review the available evidence on the chronobiological (circadian, weekly, and seasonal) patterns of onset of acute cerebrovascular diseases and variations in their possible triggering mechanisms. The existence of a peculiar chronobiological pattern in the onset of acute cerebrovascular disease, characterized by both circadian (morning and evening occurrence), circaseptan (last and first days of the week), and circannual (especially in winter) is confirmed, although differences depending on biological (gender, age), pathological (diabetes, hypertension, smoke, alcohol), cultural, social, and environmental factors exist. A deeper knowledge of the underlying pathophysiologic mechanisms could provide more effective insights for both preventive strategies and optimization of therapeutic approach.

Cold: a risk factor for stroke?

A retrospective study was performed to investigate seasonal variation in stroke incidence and to evaluate the hypothesis that cold might be a risk factor. Data were obtained from the central registry of the Hospital de S. João, Porto, Portugal, concerning 4048 patients consecutively admitted for cerebrovascular disease during a period of 33 months. Monthly admissions for stroke and its subtypes were related to mean values of ambient temperature using linear correlation. There was a strong inverse correlation between average temperature and total admissions for cerebrovascular disease (r = -0.72, P < 0.00005), intracerebral haemorrhage (r = -0.66, P < 0.00005), ischaemic stroke (r = -0.46, P = 0.007) and transient ischaemic attack (r = -0.41, P = 0.017). These correlations were independent of any seasonal variation in the number of hospital admissions due to all causes. No relation was found between temperature and subarachnoid haemorrhage. The rhythmometric analysis showed the presence of a statistically significant rhythm with an acrophase in the coldest months. These results support the hypothesis of stroke being a chronorisk disease to which cold might represent a triggering factor.

Seasonal fluctuation in the incidence of intracranial aneurysm rupture and its relationship to changing climatic conditions

Seasonal and climatic variations have been linked to the occurrence of some types of cerebrovascular disease; however, the conditions that lead to intracranial aneurysm rupture are not known. The purpose of the present study was to determine whether seasonal and climatic conditions are related to intracranial aneurysm rupture. Data provided by the Connecticut Health Information Management and Exchange were analyzed for all patients with a primary diagnosis of aneurysmal subarachnoid hemorrhage (SAH) for the fiscal years 1981, 1983, 1985, 1987, 1988, and 1989. Patient records were correlated with climatic conditions for the years 1981 to 1989 obtained from the National Climatic Data Center, National Oceanic and Atmospheric Administration, National Environmental Satellite Data, and Information Service. During the time periods studied, 1487 patients with a primary diagnosis of aneurysmal SAH were treated by reporting hospitals. Seasonal variation in the incidence of aneurysmal SAH and admission clustering were observed but differed significantly between men and women. Men showed a single large peak in late fall (Roger's r = 11.5, p < 0.005), whereas women had an annual peak occurring in late spring (Roger's r = 10.3, p < 0.01). Substantial climatic change occurred during the 72 hours prior to 10 of the 14 clusters of men who were admitted (p < 0.01, Yates' corrected chi-square 7.33, df = 1). In contrast, clusters of women admitted were not related to preceding climatic change (p > 0.25, Yates' corrected chi-square 0.06, df = 1). Hospital admissions for aneurysmal SAH display seasonal fluctuation, with women showing a different seasonal pattern from men. Changing climatic conditions precede aneurysm rupture in men but not in women, which suggests that weather is causally related to aneurysm rupture in men, and that factors that lead to aneurysm rupture in women may be different from those in men. These data do not explain why weather fronts or gradients are associated with aneurysm rupture in men.

Acute intracerebral haemorrhage: circadian and circannual patterns of onset

Hypothesis of the circannual and circadian variation in onset of intracerebral haemorrhage (CH) was verified, by means of single cosinor method and chi-square test for goodness of fit, in 161 consecutive patients (94 men and 67 women) admitted into the Institute of Neurosurgery of Ferrara Hospital, Italy, over 9 years. The majority of CH occurred in the morning between 06.00 AM and 12.00 noon (36.7% of cases, p < 0.001); when considering the specific anatomical sites, typical supratentorial haemorrhages showed a similar pattern (37.4%, p = 0.01). A similar morning behavior was found when considering subgroups by sex (men 36.2%, women 37.3%), age > or = 60 years (42.5%), no presence of hypertension (39.7%), no presence of diabetes mellitus (33.3%) and non-smokers (30.4%). The results by cosinor analysis yielded a circadian rhythmicity both for total sample and, for the men's subgroup, with a morning peak at 11.44 and 11.25, respectively. For women, however, spectral analysis found a significant ultradian cycle, having a period of 12 h (p = 0.01). A circannual periodicity, with a prevalent peak in February, was found for total sample and males subgroups, too. The results of this study confirm that intracerebral haemorrhages present a characteristic circadian and circannual pattern in onset.