Seasonal and latitudinal occurrence of cerebral vasospasm and subarachnoid hemorrhage in the northern hemisphere

Vitamin D deficiency promotes intracranial aneurysm rupture

Intracranial aneurysm rupture causes severe disability and high mortality. Epidemiological studies show a strong association between decreased vitamin D levels and an increase in aneurysm rupture. However, the causality and mechanism remain largely unknown. In this study, we tested whether vitamin D deficiency promotes aneurysm rupture and examined the underlying mechanism for the protective role of vitamin D against the development of aneurysm rupture utilizing a mouse model of intracranial aneurysm. Mice consuming a vitamin D-deficient diet had a higher rupture rate than mice with a regular diet. Vitamin D deficiency increased proinflammatory cytokines in the cerebral arteries. Concurrently, vitamin D receptor knockout mice had a higher rupture rate than the corresponding wild-type littermates. The vitamin D receptors on endothelial and vascular smooth muscle cells, but not on hematopoietic cells, mediated the effect of aneurysm rupture. Our results establish that vitamin D protects against the development of aneurysmal rupture through the vitamin D receptors on vascular endothelial and smooth muscle cells. Vitamin D supplementation may be a viable pharmacologic therapy for preventing aneurysm rupture.

Seasonal Variations in the Incidence of Ischemic Stroke, Extracranial and Intracranial Hemorrhage in Atrial Fibrillation Patients

BACKGROUND

Ischemic stroke (IS) and major bleeding, which are serious adverse events in patients with atrial fibrillation (AF), could have seasonal variations, but there are few reports.Methods and Results:In the Shinken Database 2004-2016 (n=22,018), 3,581 AF patients (average age, 63.5 years; 2,656 men, 74.2%; 1,388 persistent AF, 38.8%) were identified. Median CHADS₂and HAS-BLED scores were both 1 point. Oral anticoagulants were prescribed for 2,082 (58.1%) patients (warfarin, 1,214; direct oral anticoagulants [DOACs], 868). Incidence and observation period (maximum 3 years) of IS, extracranial hemorrhage (ECH), and intracranial hemorrhage (ICH) were counted separately for the northern hemisphere seasons. During the mean follow-up period of 2.4 years, there were totals of 90 IS, 73 ECH, and 33 ICH cases. The respective incidence rates per 1,000 patient-years in spring, summer, autumn, and winter were 8.5, 8.8, 7.5, and 16.8 for IS, 7.2, 9.7, 3.8, and 13.1 for ECH, and 2.7, 1.9, 3.8, and 7.0 for ICH. The number of patients with DOACs relatively increased among those with ECH in summer.

CONCLUSIONS

Significant seasonal variations were observed for IS, ECH, and ICH events in AF patients, and were consistently the highest in winter. A small peak of ECH was observed in summer, which seemed, in part, to be related to increased DOAC use.

[Impact of seasons, years El Nino/La Nina and rainfalls on stroke-related morbidity and mortality in Kinshasa]

INTRODUCTION

The significant impact of seasonality and climate change on stroke-related morbidity and mortality is well established, however, some findings on this issue are conflicting. The objective was to determine the impact of gender, age, season, year of admission, temperature, rainfall and El Nino phenomenon on ischemic and hemorrhagic strokes and fatal cases of stroke.

METHODS

The study was carried out at the teaching hospital of Kinshasa, DRC, between January 1998 and December 2004. Rainy and dry seasons, elevated temperatures, indices of rainfalls El Nino years 1998, 2002 and 2004, but La Nina years 1999-2000 and neutral/normal years 2001 and 2003 were defined.

RESULTS

Among 470 incident strokes, 34.5% of victims (n=162) died. Traditional seasons (small dry season, small rainy season, great dry season, great rainy season) and temperatures did not significantly (P>0.005) impact on stroke incidence. However, there was a positive association between the decrease in rainfall, El Nino, and incident ischemic strokes, but a significant positive association between the increase in rainfall, La Nina, and incident hemorrhagic strokes. Using logistic regression analysis, age ≥ 60 years (OR: 1.7, 95% CI: 1.2-2.5; P=0.018) and El Nino years (OR: 2, 95% CI: 1.2-3.3; P=0.009) were identified as the independent predictors of fatal strokes.

CONCLUSION

Early warning systems should be developed to predict the impact of seasons and climate variability on stroke morbidity and mortality.

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.

Modeling gradually changing seasonal variation in count data using state space models: a cohort study of hospitalization rates of stroke in atrial fibrillation patients in Denmark from 1977 to 2011

BACKGROUND

Seasonal variation in the occurrence of cardiovascular diseases has been recognized for decades. In particular, incidence rates of hospitalization with atrial fibrillation (AF) and stroke have shown to exhibit a seasonal variation. Stroke in AF patients is common and often severe. Obtaining a description of a possible seasonal variation in the occurrence of stroke in AF patients is crucial in clarifying risk factors for developing stroke and initiating prophylaxis treatment.

METHODS

Using a dynamic generalized linear model we were able to model gradually changing seasonal variation in hospitalization rates of stroke in AF patients from 1977 to 2011. The study population consisted of all Danes registered with a diagnosis of AF comprising 270,017 subjects. During follow-up, 39,632 subjects were hospitalized with stroke. Incidence rates of stroke in AF patients were analyzed assuming the seasonal variation being a sum of two sinusoids and a local linear trend.

RESULTS

The results showed that the peak-to-trough ratio decreased from 1.25 to 1.16 during the study period, and that the times of year for peak and trough changed slightly.

CONCLUSION

The present study indicates that using dynamic generalized linear models provides a flexible modeling approach for studying changes in seasonal variation of stroke in AF patients and yields plausible results.

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.

A 5-year retrospective study assessing the association between seasonal and meteorological change and incidence of aneurysmal subarachnoid haemorrhage

OBJECTIVE

Seasonal variation in incidence of spontaneous subarachnoid haemorrhage (SAH) is well recognised. This retrospective single-centre study aimed to characterise seasonality of SAH in the temperate climate of London, UK and to determine associations of incidence with meteorological variables. We further investigated whether associations vary according to location of aneurysm.

METHODS

Admission data on 647 patients admitted with spontaneous SAH from December 2003 to August 2008 was analysed using our neurosurgical referrals database. Average monthly incidence of SAH was correlated with local temperature, atmospheric pressure and humidity data. In a subset of 467 patients, impact of aneurysm location on seasonal variation was evaluated.

RESULTS

A non-significant bi-annual peak incidence was observed in Spring and Autumn with a trough in Summer (chi(2) = 1.5, p = 0.47). This trend was particularly marked with middle cerebral and posterior communicating artery aneurysms. However, anterior communicating artery aneurysmal SAH peaked in Summer only. SAH incidence correlated significantly with average humidity (coefficient 0.213, CI (0.02-0.404), p = 0.035) and peak humidity (coefficient 0.128, CI (0.008-0.248), p = 0.041). Temperature and atmospheric pressure did not correlate with incidence.

CONCLUSIONS

This study illustrates a pattern of variation in SAH incidence similar to that seen in other populations and climates. However, our data suggests that this pattern differs according to aneurysm location. Unusually, we also find that humidity, and not temperature or atmospheric pressure, correlates with SAH incidence. Seasonal variability in aneurysm rupture is likely to be multifactorial, but meteorological factors may play an important role.

Involvement of meteorological factors and sex in the occurrence of subarachnoid hemorrhage in Japan

The sex difference in the seasonal occurrence of subarachnoid hemorrhage (SAH) and the association of meteorological factors in Japan were analyzed in 1006 consecutive patients with SAH in Toyama, Japan from 1996 to 2000. The study investigated whether these meteorological factors could explain the seasonality of the incidence of SAH in each sex. Seasonal variation of SAH occurrence peaked in spring in men, but peaked in spring and winter in women. The difference between maximum temperature and minimum temperature was the greatest on the day previous to SAH occurrence in multiple individuals in men, whereas mean humidity was the greatest on that day in women. Interestingly, the difference between maximum temperature and minimum temperature peaked in spring and mean humidity in winter from the meteorological data over the 5 years. The relationship between humidity and occurrence of SAH may explain the sex difference of the incidence of aneurysmal SAH. The humidity change may be a specific and additional meteorological factor for the incidence of SAH in women.

Seasonal variation in hospitalization and case fatality of subarachnoid hemorrhage - a nationwide danish study on 9,367 patients

Seasonal variation in the occurrence of cerebrovascular disease has been reported, but data about subarachnoid hemorrhage (SAH) are few and inconclusive. We conducted a nationwide population-based study in Denmark to examine any seasonal pattern of hospitalization and case fatality of SAH. We identified 9,367 patients with SAH and found a modest indication of overall seasonal variation for the risk of hospitalization with this diagnosis. The seasonal pattern, with the highest incidence in January and the nadir in July, was mostly apparent for subjects aged >65 years (peak-to-trough ratio = 1.18; 95% CI 1.04-1.32). There was little difference by sex. The overall 30-day case fatality rate was 38% and showed less seasonal variation. We found evidence of weak seasonal variation in hospitalization for SAH and almost no seasonal variation in a 30-day case fatality rate after SAH.

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.

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.

Differential effects of activity and climate on onset of subarachnoid hemorrhage

Conflicting findings of the effect of climate on onset of subarachnoid hemorrhage (SAH) may result from the influence of strenuous activities which can trigger aneurysmal rupture independent of climatological factors. The effect of climate and patient activities on onset of SAH were analyzed. The clinical records of 786 consecutive patients with aneurysmal SAH admitted to our hospital for 10 years were reviewed. Activities at onset were categorized according to the intensity of strain at onset. Seasonal variation, circannual cyclic trend, and association with 90 meteorological factors were examined in each category and the results were compared between categories. Bimonthly occurrence in the light strain group showed a significant seasonal variation and cyclic trend with two peaks in early spring and fall, whereas no significant trend was detected in the overall patients and in the heavy strain group. The significant meteorological factors were global solar radiation, sunshine hours, changes in mean and minimum temperature and mean vapor pressure from the previous day, and minimum pressure in the previous 7 days. Lower global solar radiation in the light strain group was associated with onset with the lowest p value (p = 0.0046). No factors were significant in the heavy strain group. There is some evidence of the possible influence of climatological factors on onset of SAH without strenuous activity. Strenuous activity seems to affect onset more strongly, which masks any effect of climate.

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.

A population-based study of the associations of stroke occurrence with weather parameters in Siberia, Russia (1982-92)

Previous studies have established a seasonal variation in stroke occurrence, but none have assessed the influence of inclement weather conditions on stroke incidence in a general population of Russia. We performed a stroke population-based study in the Oktiabrsky District of Novosibirsk, Siberia, Russia. Included in the analysis were 1929 patients with their first occurrence of ischemic stroke (IS), 215 patients with their first occurrence of intracerebral hemorrhage (ICH) and 64 patients with their first occurrence of subarachnoid hemorrhage (SAH): all patients were aged between 25 and 74 years. The cumulative daily occurrence of total strokes and stroke subtypes was evaluated in relation to aggregated daily mean values of ambient temperature, relative humidity and air pressure by means of Poisson regression analysis to estimate the rate ratio (RR) with corresponding confidence interval (CI) and to identify the weather parameters of most importance. In a multivariate analysis, with adjustment for the effects of season, solar and geomagnetic activity, and age of the patients, low ambient temperature (RR 1.32; 95% CI 1.05-1.66) and mean value of air pressure (RR 0.986; 95% CI 0.972-0.999) were important predictors of IS occurrence, while mild ambient temperature (RR 1.52; 95% CI 1. 04-2.22) was an important predictor of ICH occurrence. No relationship between SAH occurrence and any one of the weather parameters studied was revealed. There was no interaction between any meteorological variables that was statistically significant. Inclement weather conditions are associated with the occurrence of IS and ICH in Siberia, Russia. Among the meteorological parameters studied, low ambient temperature and mean air pressure are the most important predictors of IS occurrence, whereas the occurrence of ICH is associated with mild ambient temperature. There is no association between any one of the weather parameters studied and the occurrence of SAH.

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.

Hospitalization and case-fatality rates for subarachnoid hemorrhage in Canada from 1982 through 1991. The Canadian Collaborative Study Group of Stroke Hospitalizations

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage (SAH) has a different epidemiological profile from other types of stroke and a different etiology. Although there has been a general decline in overall stroke incidence since the 1950s, secular trends for SAH have been modest. In contrast to other stroke types, changes in incidence over the last few decades have been less clear. The purpose of this study was to estimate hospitalization and case-fatality rates of SAH according to age, sex, calendar year, and season.

METHODS

Data were obtained for each of Canada's 10 provinces for the 10 fiscal years 1982 through 1991. All hospitalizations of persons 15 years of age or older with a primary diagnosis at discharge coded 430 according to the International Classification of Diseases, 9th Revision, were included. Rates of SAH per 100,000 population were calculated for men and women for 5-year age groups, by calendar year, and by season. Annual age- and sex-specific (hospital) case-fatality rates up to 30 days were also calculated. Additionally, hospital deaths from this study were related to national SAH mortality statistics.

RESULTS

A total of 14145 women and 8995 men were discharged with a primary diagnosis of SAH during the 10-year period. In contrast to other types of stroke, the rates of SAH were higher for women than for men at all ages. The age-standardized rates of SAH in 1991-1992 were 11.2 per 100000 women and 8.0 per 100000 men. For women, there was a 6% (95% confidence interval [CI], -12% to 0%) decline in hospitalization rates over that period; for men, the decline was 15% (95% CI, -21% to -8%). The peak season for SAH among women was winter; for men the peaks were in the fall and spring. For both sexes, the lowest occurrence was in the summer. Over this period, 30-day case-fatality rates declined somewhat (statistically significant only in the age group of 35 to 44 years). The number of deaths enumerated from hospital discharges was 20% to 50% lower than the number recorded on national mortality statistics, indicating that a proportion of SAH deaths occurred before (or after) the hospital stay.

CONCLUSIONS

Although rates of hospitalization for SAH declined over this period, SAH remains an important neurological event affecting individuals at relatively young ages. The rates were higher for women than for men at all ages. Total (in-hospital) case-fatality rate remains high.

Temporal patterns of stroke onset. The Framingham Study

BACKGROUND AND PURPOSE

Several studies have shown stroke onset to vary by season, day of the week, and time of day. These temporal patterns, which may provide insights into pathogenesis, were found mainly in clinical series, which can be subject to selection bias. To obtain a less distorted picture of stroke onset, we examined the month and season, day of the week, time, and place stroke occurred in a community-based cohort.

METHODS

Over a 40-year period of surveillance of the Framingham Study cohort of 5070 people aged 30 to 62 years and free of stroke and cardiovascular disease at entry, 637 completed initial strokes occurred. Month, season, day of the week, time of day, and place of occurrence of stroke were ascertained systematically and related prospectively to stroke incidence, subtype, and gender.

RESULTS

Winter was the peak season for cerebral embolic strokes. Significantly more stroke events occurred on Mondays than any other day, particularly for working men. For intracerebral hemorrhages, a third happened on Mondays in both genders. The time of day when strokes most frequently occurred was between 8 AM and noon. This pattern was true for all stroke subtypes. This pattern persisted when individuals whose onset occurred while sleeping or on awakening were excluded. Stroke in general occurred more at home, with hemorrhagic strokes occurring outside the home and cerebral embolisms in the hospital more than other subtypes.

CONCLUSIONS

Temporal patterns of stroke onset were observed for season, day of the week, time of day, and place in a community-based population. These findings suggest that there are periods of increased risk of stroke that may be amenable to preventive strategies.