Weather, season, and daily stroke admissions in Hong Kong

Do Gender and Season Modify the Triggering Effect of Ambient Temperature on Ischemic Stroke?

BACKGROUND

Ischemic stroke (IS) is a multifactorial disorder, a leading cause of long-term disability, and the second most common cause of death. Previous studies have examined the association between stroke and weather conditions with conflicting results. In this study we aimed to investigate the association between changes in ambient temperature and risk of IS onset.

METHODS

We used a time-stratified case-crossover study design including all patients admitted to Soroka University Medical Center in southern Israel between 2012 and 2014 for IS. Exposure windows of 6, 12, 24, 48, 72, and 96 hours were examined. All patients were assessed and classified by a neurologist. Temperature (°C), and relative humidity (%) were obtained from monitoring stations located in Beer-Sheva.

RESULTS

A total of 1,174 patients visited Soroka University Medical Center for admission for an IS during the study period. Among them, 56% were male, on average 69.8 ± 13.1 years old. IS incidence was associated with increase in temperature during the summer and autumn season over the 96 hours preceding symptoms onset; the odds ratio (OR) for an increase of 5°C was 3.10 (95% CI, 1.45-6.61) during the summer and 1.86 (95% CI, 1.15-2.99) in autumn. The association between temperature and stroke onset during the winter was negative (OR, 0.68; 95% CI, 0.48-0.97) for 96-hour moving average temperature exposure. Men were more sensitive to 96-hour exposure window temperature fluctuations (OR, 1.35; 95% CI, 1.01-1.80) than women (OR, 0.96; 95% CI, 0.68-1.36). We did not find any associations between IS onset and differences between the maximum and minimum measurements of temperature.

CONCLUSIONS

Our findings showed that short-term exposure to high temperatures is associated with a higher risk of IS in men but not in women. Further study is needed to validate this observation and to understand its pathophysiology.

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.

Ambient Temperature and Stroke Occurrence: A Systematic Review and Meta-Analysis

Biologically plausible associations exist between climatic conditions and stroke risk, but study results are inconsistent. We aimed to summarize current evidence on ambient temperature and overall stroke occurrence, and by age, sex, and variation of temperature. We performed a systematic literature search across MEDLINE, Embase, PsycINFO, CINAHL, Web of Science, and GEOBASE, from inception to 16 October 2015 to identify all population-based observational studies. Where possible, data were pooled for meta-analysis with Odds ratios (OR) and corresponding 95% confidence intervals (CI) by means of the random effects meta-analysis. We included 21 studies with a total of 476,511 patients. The data were varied as indicated by significant heterogeneity across studies for both ischemic stroke (IS) and intracerebral hemorrhage (ICH). Pooled OR (95% CI) in every 1 degree Celsius increase in ambient temperature was significant for ICH 0.97 (0.94–1.00), but not for IS 1.00 (0.99–1.01) and subarachnoid hemorrhage (SAH) 1.00 (0.98–1.01). Meta-analysis was not possible for the pre-specified subgroup analyses by age, sex, and variation of temperature. Change in temperature over the previous 24 h appeared to be more important than absolute temperature in relation to the risk of stroke, especially in relation to the risk of ICH. Older age appeared to increase vulnerability to low temperature for both IS and ICH. To conclude, this review shows that lower mean ambient temperature is significantly associated with the risk of ICH, but not with IS and SAH. Larger temperature changes were associated with higher stroke rates in the elderly.

Ambient temperature and risk of cardiovascular hospitalization: An updated systematic review and meta-analysis

The association between temperatures and risk of cardiovascular mortality has been recognized but the association drawn from previous meta-analysis was weak due to the lack of sufficient studies. This paper presented a review with updated reports in the literature about the risk of cardiovascular hospitalization in relation to different temperature exposures and examined the dose-response relationship of temperature-cardiovascular hospitalization by change in units of temperature, latitudes, and lag days. The pooled effect sizes were calculated for cold, heat, heatwave, and diurnal variation using random-effects meta-analysis, and the dose-response relationship of temperature-cardiovascular admission was modelled using random-effect meta-regression. The Cochrane Q-test and index of heterogeneity (I(2)) were used to evaluate heterogeneity, and Egger's test was used to evaluate publication bias. Sixty-four studies were included in meta-analysis. The pooled results suggest that for a change in temperature condition, the risk of cardiovascular hospitalization increased 2.8% (RR, 1.028; 95% CI, 1.021-1.035) for cold exposure, 2.2% (RR, 1.022; 95% CI, 1.006-1.039) for heatwave exposure, and 0.7% (RR, 1.007; 95% CI, 1.002-1.012) for an increase in diurnal temperature. However no association was observed for heat exposure. The significant dose-response relationship of temperature - cardiovascular admission was found with cold exposure and diurnal temperature. Increase in one-day lag caused a marginal reduction in risk of cardiovascular hospitalizations for cold exposure and diurnal variation, and increase in latitude was associated with a decrease in risk of cardiovascular hospitalizations for diurnal temperature only. There is a significant short-term effect of cold exposure, heatwave and diurnal variation on cardiovascular hospitalizations. Further research is needed to understand the temperature-cardiovascular relationship for different climate areas.

[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.

Time series analysis of the association between ambient temperature and cerebrovascular morbidity in the elderly in Shanghai, China

Research on the association between ambient temperature and cerebrovascular morbidity is scarce in China. In this study, we applied mixed generalized additive model (MGAM) to daily counts of cerebrovascular disease of Shanghai residents aged 65 years or older from 2007-2011, stratified by gender. Weighted daily mean temperature up to lags of one week was smoothed by natural cubic spline, and was added into the model to assess both linear and nonlinear effects of temperature. We found that when the mean temperature increased by 1 °C, the male cases of cerebrovascular disease reduced by 0.95% (95% Confidence Interval (CI): 0.80%, 1.10%) or reduced by 0.34% (95% CI: -0.68, 1.36%) in conditions of temperature was below or above 27 °C. However, for every 1 °C increase in temperature, the female cases of cerebrovascular disease increased by 0.34% (95% CI: -0.26%, 0.94%) or decreased by 0.92% (95% CI: 0.72, 1.11%) in conditions of temperature was below or above 8 °C, respectively. Temperature and cerebrovascular morbidity is negatively associated in Shanghai. MGAM is recommended in assessing the association between environmental hazards and health outcomes in time series studies.

Humidity: A review and primer on atmospheric moisture and human health

Research examining associations between weather and human health frequently includes the effects of atmospheric humidity. A large number of humidity variables have been developed for numerous purposes, but little guidance is available to health researchers regarding appropriate variable selection. We examine a suite of commonly used humidity variables and summarize both the medical and biometeorological literature on associations between humidity and human health. As an example of the importance of humidity variable selection, we correlate numerous hourly humidity variables to daily respiratory syncytial virus isolates in Singapore from 1992 to 1994. Most water-vapor mass based variables (specific humidity, absolute humidity, mixing ratio, dewpoint temperature, vapor pressure) exhibit comparable correlations. Variables that include a thermal component (relative humidity, dewpoint depression, saturation vapor pressure) exhibit strong diurnality and seasonality. Humidity variable selection must be dictated by the underlying research question. Despite being the most commonly used humidity variable, relative humidity should be used sparingly and avoided in cases when the proximity to saturation is not medically relevant. Care must be taken in averaging certain humidity variables daily or seasonally to avoid statistical biasing associated with variables that are inherently diurnal through their relationship to temperature.

The acute effects of outdoor temperature on blood pressure in a panel of elderly hypertensive patients

Higher level of blood pressure (BP) in winter than in summer has been observed, but the association between temperature and BP and its potential modifiers with adjustment of individual confounders and time trends was rarely explored. We aimed to investigate the association between outdoor temperature and BP and its potential modification factors in a longitudinal panel study in Shanghai, China. From January 2011 to December 2012, we scheduled 54 follow-ups for BP measurements per subject via home visit every other week for 50 elderly hypertensive patients. We applied linear mixed-effect models to analyze the association between temperature and BP after controlling for individual characteristics, antihypertensive medication, comorbidities, and time trends. We evaluated the potential effect modifiers by stratification analyses. For a 1 °C decrease in the average temperature on concurrent day and previous day, systolic BP increased by 0.19 mmHg (95 % confidence interval = 0.06, 0.31) and diastolic BP increased by 0.12 mmHg (95 % confidence interval = 0.03, 0.21). The effect of temperature on BP was stronger among those with older age, female sex, low socioeconomic status, and obese physique. The effect was weak and even null for those taking the angiotensin receptor blockers, angiotensin-converting enzyme inhibitor, or its combination with calcium antagonists. Further, the effect was almost restricted within those having chronic comorbidities. Our results demonstrated that an acute decrease in outdoor temperature was significantly associated with a rise in BP among elderly hypertensive patients, in Shanghai, China. Individual characteristics, antihypertensive medications, and comorbidities may modify this effect.

Ambient Temperature and Cerebrovascular Hemodynamics in the Elderly

BACKGROUND AND PURPOSE

Some prior studies have linked ambient temperature with risk of cerebrovascular events. If causal, the pathophysiologic mechanisms underlying this putative association remain unknown. Temperature-related changes in cerebral vascular function may play a role, but this hypothesis has not been previously evaluated.

METHODS

We evaluated the association between ambient temperature and cerebral vascular function among 432 participants ≥65 years old from the MOBILIZE Boston Study with data on cerebrovascular blood flow, cerebrovascular resistance, and cerebrovascular reactivity in the middle cerebral artery. We used linear regression models to assess the association of mean ambient temperature in the previous 1 to 28 days with cerebrovascular hemodynamics adjusting for potential confounding factors.

RESULTS

A 10°C increase in the 21-day moving average of ambient temperature was associated with a 10.1% (95% confidence interval [CI], 2.2%, 17.3%) lower blood flow velocity, a 9.0% (95% CI, 0.7%, 18.0%) higher cerebrovascular resistance, and a 15.3% (95%CI, 2.7%, 26.4%) lower cerebral vasoreactivity. Further adjustment for ozone and fine particulate matter (PM2.5) did not materially alter the results. However, we found statistically significant interactions between ambient temperature and PM2.5 such that the association between temperature and blood flow velocity was attenuated at higher levels of PM2.5.

CONCLUSIONS

In this elderly population, we found that ambient temperature was negatively associated with cerebral blood flow velocity and cerebrovascular vasoreactivity and positively associated with cerebrovascular resistance. Changes in vascular function may partly underlie the observed associations between ambient temperature and risk of cerebrovascular events.

Short-Term Effect of Ambient Temperature and the Risk of Stroke: A Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

The relationship between stroke and short-term temperature changes remains controversial. Therefore, we conducted a systematic review and meta-analysis to investigate the association between stroke and both high and low temperatures, and health assessment.

METHODS

We searched PubMed, Embase, Cochrane, China National Knowledge Infrastructure (CNKI) and Wanfang Data up to 14 September 2014. Study selection, quality assessment, and author-contractions were steps before data extraction. We converted all estimates effects into relative risk (RR) per 1 °C increase/decrease in temperature from 75th to 99th or 25th to 1st percentiles, then conducted meta-analyses to combine the ultimate RRs, and assessed health impact among the population.

RESULTS

20 articles were included in the final analysis. The overall analysis showed a positive relationship between 1 °C change and the occurrence of major adverse cerebrovascular events (MACBE), 1.1% (95% confidence intervals (CI), 0.6 to 1.7) and 1.2% (95% CI, 0.8 to 1.6) increase for hot and cold effects separately. The same trends can be found in both effects of mortality and the cold effect for morbidity. Hot temperature acted as a protective factor of hemorrhage stroke (HS), -1.9% (95% CI, -2.8 to -0.9), however, it acted as a risk factor for ischemic stroke (IS), 1.2% (95% CI, 0.7 to 1.8).

CONCLUSION

Short-term changes of both low and high temperature had statistically significant impacts on MACBE.

The association between weather conditions and stroke admissions in Turkey

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

The Trends in Excess Mortality in Winter vs. Summer in a Sub-Tropical City and Its Association with Extreme Climate Conditions

While there is literature on excess winter mortality, there are few studies examining the evolution of its trend which may be changing in parallel with global warming. This study aimed to examine the trend in the excess mortality in winter as compared to summer among the older population in a sub-tropical city and to explore its association with extreme weather. We used a retrospective study based on the registered deaths among the older population in Hong Kong during 1976-2010. An Excess Mortality for Winter versus Summer (EMWS) Index was used to quantify the excess number of deaths in winter compared to summer. Multiple linear regressions were used to analyze the trends and its association with extreme weather. Overall, the EMWS Index for ischemic heart disease, cerebrovascular diseases, chronic lower respiratory diseases, pneumonia, and other causes were 43.0%, 34.2%, 42.7%, 23.4% and 17.6%, respectively. Significant decline was observed in the EMWS Index for chronic lower respiratory diseases and other causes. The trend in the index for cerebrovascular diseases depended on the age group, with older groups showing a decline but younger groups not showing any trend. Meteorological variables, in terms of extreme weather, were associated with the trends in the EMWS Index. We concluded that shrinking excess winter mortality from cerebrovascular diseases and chronic lower respiratory diseases was found in a sub-tropical city. These trends were associated with extreme weather, which coincided with global warming.

Effects of Meteorological Conditions on the Risk of Ischemic Stroke Events in Patients Treated with Alteplase--HEWS-tPA

BACKGROUND

Predicting a day that presents a high risk for the occurrence of ischemic stroke events may enable health professionals to prepare for emergency stroke therapy more properly. We evaluated the association between meteorological conditions and the frequency of ischemic stroke events in Japanese patients.

METHODS

Ischemic stroke patients (n = 299) who were treated with alteplase at 9 stroke hospitals in 3 restricted areas were examined. The daily rates of ischemic stroke events were compared with the daily mean thermo-hydrological index (THI), the atmospheric pressure, and the daily changes of these variables for the 6 days preceding an ischemic stroke event using Poisson regression analysis.

RESULTS

We trisected onset days based on the THI (low-temperature, intermediate-temperature, and high-temperature), atmospheric pressure (low-pressure, intermediate-pressure, and high-pressure), changes in THI for preceding 6 days from the previous day (cooler, unchanged-temperature, and warmer), and changes in atmospheric pressure (decreased-pressure, unchanged-pressure, and increased-pressure). The frequency of ischemic stroke was significantly higher on low-temperature or high-pressure days (risk ratio, 1.398, P = .022; risk ratio, 1.374, P = .039), on warmer-temperature days, and when atmospheric pressure varied from the day before (P < .05). There were significantly lower risks for ischemic stroke events on cooler-temperature days, and higher risks were associated with a variation in atmospheric pressure 3 days before the onset from 4 days before (P < .05).

CONCLUSIONS

There were higher risks for ischemic stroke events associated with low ambient temperature, high atmospheric pressure, increased temperature, and varied atmospheric pressure. Also, atmospheric pressure variation 3 days before may be associated.

Association with meteo-climatological factors and daily emergency visits for renal colic and urinary calculi in Cuneo, Italy. A retrospective observational study, 2007-2010

The incidence of nephrolithiasis is rising worldwide, especially in women and with increasing age. Incidence and prevalence of kidney stones are affected by genetic, nutritional, and environmental factors. The aim of this study is to investigate the link between various meteorological factors (independent variables) and the daily number of visits to the Emergency Department (ED of the S. Croce and Carle Hospital of Cuneo for renal colic (RC) and urinary stones (UC) as the dependent variable over the years 2007-2010.The Poisson generalized regression models (PGAMs) have been used in different progressive ways. The results of PGAMs (stage 1) adjusted for seasonal and calendar factors confirmed a significant correlation (p < 0.03) with the thermal parameter. Evaluation of the dose-response effect [PGAMs combined with distributed lags nonlinear models (DLNMs)-stage 2], expressed in terms of relative risk (RR) and cumulative relative risk (RRC), indicated a relative significant effect up to 15 lag days of lag (RR > 1), with a first peak after 5 days (lag ranges 0-1, 0-3, and 0-5) and a second weak peak observed along the 5-15 lag range days. The estimated RR for females was significant, mainly in the second and fourth age group considered (19-44 and >65 years): RR for total ED visits 1.27, confidence interval (CI) 1.11-1.46 (lag 0-5 days); RR 1.42, CI 1.01-2.01 (lag 0-10 days); and RR 1.35, CI 1.09-1.68 (lag 0-15 days). The research also indicated a moderate involvement of the thermal factor in the onset of RC caused by UC, exclusively in the female sex. Further studies will be necessary to confirm these results.

The influence of weather on health-related help-seeking behavior of senior citizens in Hong Kong

It is believed that extreme hot and cold weather has a negative impact on general health conditions. Much research focuses on mortality, but there is relatively little community health research. This study is aimed at identifying high-risk groups who are sensitive to extreme weather conditions, in particular, very hot and cold days, through an analysis of the health-related help-seeking patterns of over 60,000 Personal Emergency Link (PE-link) users in Hong Kong relative to weather conditions. In the study, 1,659,716 PE-link calls to the help center were analyzed. Results showed that females, older elderly, people who did not live alone, non-subsidized (relatively high-income) users, and those without medical histories of heart disease, hypertension, stroke, and diabetes were more sensitive to extreme weather condition. The results suggest that using official government weather forecast reports to predict health-related help-seeking behavior is feasible. An evidence-based strategic plan could be formulated by using a method similar to that used in this study to identify high-risk groups. Preventive measures could be established for protecting the target groups when extreme weather conditions are forecasted.

Meteorological Variables Associated with Stroke

To elucidate relationships between meteorological variables and incidence of stroke, we studied patients diagnosed with stroke after presenting to the emergency department (May 1, 2010–August 8, 2011). Patient demographics and medical data were reviewed retrospectively with regional meteorological data. Across 467 days, 134 stroke events were recorded on 114 days. On stroke days, maximum temperature (max T) and atmospheric pressure (AP) combined were a significant predictor of stroke (max T odds ratio (OR) = 1.014, 95% confidence interval (CI) = 1.003–1.026, and P = 0.04; AP: OR = 1.033, 95% CI = 0.997–1.071, and P = 0.02). When the patient could identify the hour of the stroke, average temperature (avg T) was significantly higher than nonstroke hours (18.2°C versus 16.16°C, P = 0.04). Daily fluctuations in AP and avg T also had significant effects on stroke incidence (AP: OR = 0.629, 95% CI = 0.512–0.773, and P = 0.0001; avg T OR = 1.1399, 95% CI = 1.218–606, and P = 0.0001). Patient age, stroke history, body mass index, ethnicity, and sex were further contributors to stroke risk. Temperature, atmospheric pressure, and certain physiological conditions likely play roles in weather-related stroke susceptibility. The mechanisms driving these associations are not fully understood.

Age and meteorological factors in the occurrence of spontaneous intracerebral hemorrhage in a metropolitan city

Objective

The aim of this study was to investigate the correlation between meteorological factors and occurrence of spontaneous intracerebral hemorrhage (ICH) according to age.

Materials and Methods

We retrospectively analyzed the records of 735 ICH patients in a metropolitan hospital-based population. Observed and expected numbers of ICH patients were obtained at 5℃ intervals of ambient temperature and a ratio of observed to expected frequency was then calculated. Changes in ambient temperature from the day before ICH onset day were observed. The Wilcoxon-Mann-Whitney test was used to test differences in meteorological variables between the onset and non-onset days. The Kruskal-Wallis test was used for comparison of meteorological variables across gender and age.

Results

ICH was observed more frequently (observed/expected ratio ≥ 1) at lower mean, minimum, and maximum ambient temperature (p = 0.0002, 0.0003, and 0.0002, respectively). Significantly lower mean, minimum, and maximum ambient temperature, dew point temperature, wind speed, and atmospheric pressure (p = 0.0003, 0.0005, 0.0001, 0.0013, 0.0431, and 0.0453, respectively) was observed for days on which spontaneous ICH occurred. In the subgroup analysis, the ICH onset day showed significantly lower mean, minimum, and maximum ambient temperature, dew point temperature, relative humidity, and higher atmospheric pressure in the older (≥ 65 years) female group (p = 0.0093, 0.0077, 0.0165, 0.0028, 0.0055, and 0.0205, respectively).

Conclusion

Occurrence of spontaneous ICH is closely associated with meteorological factors and older females are more susceptible to lower ambient temperature.

Effects of sudden air pressure changes on hospital admissions for cardiovascular diseases in Prague, 1994-2009

Sudden weather changes have long been thought to be associated with negative impacts on human health, but relatively few studies have attempted to quantify these relationships. We use large 6-h changes in atmospheric pressure as a proxy for sudden weather changes and evaluate their association with hospital admissions for cardiovascular diseases (CVD). Winter and summer seasons and positive and negative pressure changes are analysed separately, using data for the city of Prague (population 1.2 million) over a 16-year period (1994-2009). We found that sudden pressure drops in winter are associated with significant rise in hospital admissions. Increased CVD morbidity was observed neither for pressure drops in summer nor pressure increases in any season. Analysis of synoptic weather maps shows that large pressure drops in winter are associated with strong zonal flow and rapidly moving low-pressure systems with centres over northern Europe and atmospheric fronts affecting western and central Europe. Analysis of links between passages of strong atmospheric fronts and hospital admissions, however, shows that the links disappear if weather changes are characterised by frontal passages. Sudden pressure drops in winter are associated also with significant excess CVD mortality. As climate models project strengthening of zonal circulation in winter and increased frequency of windstorms, the negative effects of such weather phenomena and their possible changes in a warmer climate of the twenty-first century need to be better understood, particularly as their importance in inducing excess morbidity and mortality in winter may increase compared to cold spells.

Sunlight exposure and cardiovascular risk factors in the REGARDS study: a cross-sectional split-sample analysis

Background

Previous research has suggested that vitamin D and sunlight are related to cardiovascular outcomes, but associations between sunlight and risk factors have not been investigated. We examined whether increased sunlight exposure was related to improved cardiovascular risk factor status.

Methods

Residential histories merged with satellite, ground monitor, and model reanalysis data were used to determine previous-year sunlight radiation exposure for 17,773 black and white participants aged 45+ from the US. Exploratory and confirmatory analyses were performed by randomly dividing the sample into halves. Logistic regression models were used to examine relationships with cardiovascular risk factors.

Results

The lowest, compared to the highest quartile of insolation exposure was associated with lower high-density lipoprotein levels in adjusted exploratory (−2.7 mg/dL [95% confidence interval: −4.2, −1.2]) and confirmatory (−1.5 mg/dL [95% confidence interval: −3.0, −0.1]) models. The lowest, compared to the highest quartile of insolation exposure was associated with higher systolic blood pressure levels in unadjusted exploratory and confirmatory, as well as the adjusted exploratory model (2.3 mmHg [95% confidence interval: 0.8, 3.8]), but not the adjusted confirmatory model (1.6 mg/dL [95% confidence interval: −0.5, 3.7]).

Conclusions

The results of this study suggest that lower long-term sunlight exposure has an association with lower high-density lipoprotein levels. However, all associations were weak, thus it is not known if insolation may affect cardiovascular outcomes through these risk factors.

Short-term changes in ambient temperature and risk of ischemic stroke

Background

Despite consistent evidence of a higher short-term risk of cardiovascular mortality associated with ambient temperature, there have been discrepant findings on the association between temperature and ischemic stroke. Moreover, few studies have considered potential confounding by ambient fine particulate matter air pollution <2.5 μm in diameter (PM_2.5) and none have examined the impact of temperature changes on stroke in the subsequent hours rather than days. The aim of this study was to evaluate whether changes in temperature trigger an ischemic stroke in the following hours and days and whether humid days are particularly harmful.

Methods

We reviewed the medical records of 1,705 patients residing in the metropolitan region of Boston, Mass., USA, who were hospitalized with neurologist-confirmed ischemic stroke, and we abstracted data on the time of symptom onset and clinical characteristics. We obtained hourly meteorological data from the National Weather Service station and hourly PM_2.5 data from the Harvard ambient monitoring station. We used the time-stratified case-crossover design to assess the association between ischemic stroke and apparent temperature averaged over 1-7 days prior to stroke onset adjusting for PM_2.5. We assessed whether differences in apparent temperature trigger a stroke within shorter time periods by examining the association between stroke onset and apparent temperature levels averaged in 2-hour increments prior to stroke onset (0-2 h through 36-38 h). We tested whether the association varied by health characteristics or by PM_2.5, ozone or relative humidity.

Results

The incidence rate ratio of ischemic stroke was 1.09 (95% confidence interval 1.01-1.18) following a 5°C decrement in average apparent temperature over the 2 days preceding symptom onset. The higher risk associated with cooler temperatures peaked in the first 14-34 h. There was no statistically significant difference in the association between temperature and ischemic stroke across seasons. The risk of ischemic stroke was not meaningfully different across subgroups of patients defined by health characteristics. The association between ischemic stroke and ambient temperature was stronger on days with higher levels of relative humidity.

Conclusions

Lower temperatures are associated with a higher risk of ischemic stroke onset in both warm and cool seasons, and the risk is higher on days with higher levels of relative humidity. Based on this study and the body of literature on ambient temperature and cardiovascular events, identifying methods for mitigating cardiovascular risk may be warranted.

Ischemic stroke hospital admission associated with ambient temperature in Jinan, China

BACKGROUND

This study estimated the effects of ambient temperature and relative humidity on hospital admissions for ischemic stroke during 1990-2009 in Jinan, China.

METHODS

To account for possible delayed effects and harvesting effect, we examined the impact of meteorological factors up to 30 days before each admission using a distributed lag non-linear model; we controlled for season, long-term trend, day of week and public holidays in the analysis. Stratified analyses were also done for summer and winter.

RESULTS

A total of 1,908 ischemic stroke hospital admissions were observed between 1990 and 2009. We found a strong non-linear acute effect of daily temperatures on ischemic stroke hospital admission. With the mean temperature 15°C as the reference, the relative risk (RR) was 1.43 (95% confidence interval (CI): 1.10-1.85) for 0°C daily temperature on the same day, and 0.43 (95% CI: 0.31-0.59) for 30°C daily temperature on the same day, respectively. The effect of ambient temperature was similar in summer and winter. No significant association was observed between relative humidity and ischemic stroke hospitalization.

CONCLUSIONS

Low temperature might be a risk factor for ischemic stroke, and high temperature might be protective factor of ischemic stroke occurrence in Jinan, China.

Both low and high temperature may increase the risk of stroke mortality

OBJECTIVE

To examine temperature in relation to stroke mortality in a multicity time series study in China.

METHODS

We obtained data on daily temperature and mortality from 8 large cities in China. We used quasi-Poisson generalized additive models and distributed lag nonlinear models to estimate the accumulative effects of temperature on stroke mortality across multiple days, adjusting for long-term and seasonal trends, day of the week, air pollution, and relative humidity. We applied the Bayesian hierarchical model to pool city-specific effect estimates.

RESULTS

Both cold and hot temperatures were associated with increased risk of stroke mortality. The potential effect of cold temperature might last more than 2 weeks. The pooled relative risks of extreme cold (first percentile of temperature) and cold (10th percentile of temperature) temperatures over lags 0-14 days were 1.39 (95% posterior intervals [PI] 1.18-1.64) and 1.11 (95% PI 1.06-1.17), compared with the 25th percentile of temperature. In contrast, the effect of hot temperature was more immediate. The relative risks of stroke mortality over lags 0-3 days were 1.06 (95% PI 1.02-1.10) for extreme hot temperature (99th percentile of temperature) and 1.14 (95% PI 1.05-1.24) for hot temperature (90th percentile of temperature), compared with the 75th percentile of temperature.

CONCLUSIONS

This study showed that both cold and hot temperatures were associated with increased risk of stroke mortality in China. Our findings may have important implications for stroke prevention in China.

The effects of heat stress and its effect modifiers on stroke hospitalizations in Allegheny County, Pennsylvania

PURPOSE

Heat has been known to increase the risk of many health endpoints. However, few studies have examined its effects on stroke. The objective of this case-crossover study is to investigate the effects of high heat and its effect modifiers on the risk of stroke hospitalization in Allegheny County, Pennsylvania.

METHODS

We obtained data on first stroke hospitalizations among adults ages 65 and older and daily meteorological information during warm seasons (May-September) from 1994 to 2000 in Allegheny County, Pennsylvania. Using conditional multiple logistic regressions, the effects of heat days (any day with a temperature greater than the 95th percentile) and heat wave days (at least two continuous heat days) on the risk of stroke hospitalization were investigated. The potential interactions between high heat and age, type of stroke, and gender were also examined.

RESULTS

Heat day and heat wave at lag-2 day were significantly associated with an increased risk for stroke hospitalization (OR 1.121, 95 % CI 1.013-1.242; OR 1.173, 95 % CI 1.047-1.315, respectively) after adjusting for important covariates. In addition, having two or more heat wave days within the 4 day window prior to the event was also significantly associated with an increased risk (OR 1.119, 95 % CI 1.004, 1.246) compared to having no heat wave days during the period. The effect of high heat on stroke was more significant for ischemic stroke, men, and subjects ages 80 years or older.

CONCLUSIONS

Our study suggests that high heat may have adverse effects on stroke and that some subgroups may be particularly susceptible to heat.