Extreme temperature and out-of-hospital-cardiac-arrest. Nationwide study in a hot climate country

Mortality risk and burden of sudden cardiac arrest associated with hot nights, heatwaves, cold spells, and non-optimum temperatures in 0.88 million patients: An individual-level case-crossover study

Sudden cardiac arrest (SCA) is a global health concern, imposing a substantial mortality burden. However, the understanding of the impact of various extreme temperature events, when accounting for the effect of daily average temperature on SCA, remains incomplete. Additionally, the assessment of SCA mortality burden associated with temperatures from an individual-level design is limited. This nationwide case-crossover study collected individual SCA death records across all (2844) county-level administrative units in the Chinese Mainland from 2013 to 2019. Four definitions for hot nights and ten for both cold spells and heatwaves were established using various temperature thresholds and durations. Conditional logistic regression models combined with distributed lag nonlinear models were employed to estimate the cumulative exposure-response relationships. Based on 887,662 SCA decedents, this analysis found that both hot nights [odds ratio (OR): 1.28; attributable fraction (AF): 1.32 %] and heatwaves (OR: 1.40; AF: 1.29 %) exhibited significant added effects on SCA mortality independent of daily average temperatures, while cold spells were not associated with an elevated SCA risk after accounting for effects of temperatures. Cold temperatures [below the minimum mortality temperature (MMT)] accounted for a larger mortality burden than high temperatures (above the MMT) [AF: 12.2 % vs. 1.5 %]. Higher temperature-related mortality risks and burdens were observed in patients who experienced out-of-hospital cardiac arrest compared to those with in-hospital cardiac arrest. This nationwide study presents the most compelling and comprehensive evidence of the elevated mortality risk and burden of SCA associated with extreme temperature events and ambient temperatures amid global warming.

Short-term exposures to temperature and risk of sudden cardiac death in women: A case-crossover analysis in the Nurses' Health Study

Background

Sudden cardiac death (SCD) is a major source of mortality and is the first manifestation of heart disease for most cases. Thus, there is a definite need to identify risk factors for SCD that can be modified on the population level. Short-term exposures to temperature have been implicated as a potential risk factor. Our objective was to determine if short-term temperature exposures were associated with increased risk of SCD in a US-based time-stratified case-crossover study.

Methods

A total of 465 cases of SCD were identified among participants of the prospective Nurses' Health Study (NHS). Control days were selected from all other matching days of the week within the same month as the case day. Average ambient temperature on the current day (Lag0) and preceding 27 days (Lags1-27) was determined at the residence level using 800-m resolution estimates. Conditional logistic distributed lag nonlinear models (DLNMs) were used to assess the relative risk (RR) of the full range of temperature exposures over the lag period.

Results

Warmer exposures in the days before event and colder temperatures 21-28 days prior were associated with increased risks of SCD. These results were driven by associations in regions other than the Northeast and among married women.

Conclusions

Both warm and cold ambient temperatures are suggestively associated with risks of SCD among middle-aged and older women living across the United States.

The rural CPR outreach project: Medical students teach bystander CPR to secondary school students

INTRODUCTION

Prompt bystander cardiopulmonary resuscitation (CPR) can double the chance of cardiac arrest survival. Rural and remote communities experience longer emergency service wait times and have lower rates of bystander-CPR compared to their urban counterparts. Our study addresses this disparity.

METHODS

We designed a 1.5-h free hands-only CPR course tailored to secondary school students in rural and remote communities taught by medical students. We evaluated our course using pre-test and post-test surveys.

RESULTS

We taught over 300 secondary students in 5 days. Less than one-third of students had previously taken a CPR course. We found that brief CPR instruction taught by medical students was effective in both improving students' knowledge of CPR (t[528] = -26, P < 0.01) and perceived comfort in performing CPR (t[548] = -12, P < 0.01).

CONCLUSION

CPR courses taught by medical students are effective, low cost, and may help address regional health care disparities. Teaching CPR to rural/remote communities may have secondary benefits such as promoting health care careers to rural youth. We encourage other health professional programmes to consider engaging students in CPR outreach projects.

INTRODUCTION

Une réanimation cardio-pulmonaire rapide peut doubler les chances de survie en cas d'arrêt cardiaque. Les communautés rurales et éloignées connaissent des temps d'attente plus longs dans les services d'urgence et ont des taux plus faibles de RCP par rapport à leurs homologues urbains. Notre étude porte sur cette disparité.

MTHODES

Nous avons conçu un cours de RCP pratique et gratuit d'une heure et demie, adapté aux élèves du secondaire des communautés rurales et isolées et dispensé par des étudiants en médecine. Nous avons évalué notre cours à l'aide d'enquêtes pré-test et post-test.

RSULTATS

En 5 jours, nous avons enseigné à plus de 300 élèves du secondaire. Moins d'un tiers des élèves avaient déjà suivi un cours de RCP. Nous avons constaté qu'une brève formation à la RCP dispensée par des étudiants en médecine était efficace pour améliorer les connaissances des élèves en matière de RCP (t[528] = -26, P < 0,01) et la perception de leur aisance à pratiquer la RCP (t[548] = -12, P < 0,01).

CONCLUSION

Les cours de RCP dispensés par les étudiants en médecine sont efficaces, peu coûteux et peuvent contribuer à lutter contre les disparités régionales en matière de soins de santé. L'enseignement de la RCP aux communautés rurales/éloignées peut avoir des avantages secondaires tels que la promotion des carrières dans le domaine de la santé auprès des jeunes ruraux. Nous encourageons d'autres programmes professionnels de santé à envisager d'engager leurs étudiants dans des projets de sensibilisation à la RCP.

The Impact of Climate Change and Extreme Weather Conditions on Cardiovascular Health and Acute Cardiovascular Diseases

Climate change is widely recognized as one of the most significant challenges facing our planet and human civilization. Human activities such as the burning of fossil fuels, deforestation, and industrial processes release greenhouse gases into the atmosphere, leading to a warming of the Earth's climate. The relationship between climate change and cardiovascular (CV) health, mediated by air pollution and increased ambient temperatures, is complex and very heterogeneous. The main mechanisms underlying the pathogenesis of CV disease at extreme temperatures involve several regulatory pathways, including temperature-sympathetic reactivity, the cold-activated renin-angiotensin system, dehydration, extreme temperature-induced electrolyte imbalances, and heat stroke-induced systemic inflammatory responses. The interplay of these mechanisms may vary based on individual factors, environmental conditions, and an overall health background. The net outcome is a significant increase in CV mortality and a higher incidence of hypertension, type II diabetes mellitus, acute myocardial infarction (AMI), heart failure, and cardiac arrhythmias. Patients with pre-existing CV disorders may be more vulnerable to the effects of global warming and extreme temperatures. There is an urgent need for a comprehensive intervention that spans from the individual level to a systemic or global approach to effectively address this existential problem. Future programs aimed at reducing CV and environmental burdens should require cross-disciplinary collaboration involving physicians, researchers, public health workers, political scientists, legislators, and national leaders to mitigate the effects of climate change.

Heatwave Definition and Impact on Cardiovascular Health: A Systematic Review

Objectives: We aimed to analyze recent literature on heat effects on cardiovascular morbidity and mortality, focusing on the adopted heat definitions and their eventual impact on the results of the analysis. Methods: The search was performed on PubMed, ScienceDirect, and Scopus databases: 54 articles, published between January 2018 and September 2022, were selected as relevant. Results: In total, 21 different combinations of criteria were found for defining heat, 12 of which were based on air temperature, while the others combined it with other meteorological factors. By a simulation study, we showed how such complex indices could result in different values at reference conditions depending on temperature. Heat thresholds, mostly set using percentile or absolute values of the index, were applied to compare the risk of a cardiovascular health event in heat days with the respective risk in non-heat days. The larger threshold's deviation from the mean annual temperature, as well as higher temperature thresholds within the same study location, led to stronger negative effects. Conclusion: To better analyze trends in the characteristics of heatwaves, and their impact on cardiovascular health, an international harmonization effort to define a common standard is recommendable.

Association of low and high ambient temperature with mortality for cardiorespiratory diseases in Brazil

Extreme temperatures are a major public health concern, as they have been linked to an increased risk of mortality from circulatory and respiratory diseases. Brazil, a country with vast geographic and climatic variations, is particularly vulnerable to the health impacts of extreme temperatures. In this study, we examined the nationwide (considering 5572 municipalities) association of low and high ambient temperature (1st and 99th percentiles) with daily mortality for circulatory and respiratory diseases in Brazil between 2003 and 2017. We used an extension of the two-stage time-series design. First, we applied a case time series design in combination with distributed lag non-linear modeling (DLMN) framework to assess the association by Brazilian region. Here, the analyses were stratified by sex, age group (15-45, 46-65, and >65 years), and cause of death (respiratory and circulatory mortality). In the second stage, we performed a meta-analysis to estimate pooled effects across the Brazilian regions. Our study population included 1,071,090 death records due to cardiorespiratory diseases in Brazil over the study period. We found increased risk of respiratory and circulatory mortality associated with low and high ambient temperatures. The pooled national results for the whole population (all ages and sex) suggest a relative risk (RR) of 1.27 (95% CI: 1.16; 1.37) and 1.11 (95% CI: 1.01; 1.21) associated with circulatory mortality during cold and heat exposure, respectively. For respiratory mortality, we estimated a RR of 1.16 (95% CI: 1.08; 1.25) during cold exposure and a RR of 1.14 (95% CI: 0.99; 1.28) during heat exposure. The national meta-analysis indicated robust positive associations for circulatory mortality on cold days across several subgroups by sex and age, while only a few subgroups presented robust positive associations for circulatory mortality on warm days and respiratory mortality on both cold and warm days. These findings have important public health implications for Brazil and suggest the need for targeted interventions to mitigate the adverse effects of extreme temperatures on human health.

Heat, heatwaves, and ambulance service use: a systematic review and meta-analysis of epidemiological evidence

Ambulance data has been reported to be a sensitive indicator of health service use during hot days, but there is no comprehensive summary of the quantitative association between heat and ambulance dispatches. We conducted a systematic review and meta-analysis to retrieve and synthesise evidence published up to 31 August 2022 about the association between heat, prolonged heat (i.e. heatwaves), and the risk of ambulance dispatches. We initially identified 3628 peer-reviewed papers and included 48 papers which satisfied the inclusion criteria. The meta-analyses showed that, for each 5 °C increase in mean temperature, the risk of ambulance dispatches for all causes and for cardiovascular diseases increased by 7% (95% confidence interval (CI): 5%, 10%) and 2% (95% CI: 1%, 3%), respectively, but not for respiratory diseases. The risk of ambulance dispatches increased by 6% (95% CI: 4%, 7%), 7% (95% CI: 5%, 9%), and 18% (95% CI: 12%, 23%) under low-intensity, severe, and extreme heatwaves, respectively. We observed two potential sources of bias in the existing literature: (1) bias in temperature exposure measurement; and (2) bias in the ascertainment of ambulance dispatch causes. This review suggests that heat exposure is associated with an increased risk of ambulance dispatches, and there is a dose-response relationship between heatwave intensity and the risk of ambulance dispatches. For future studies assessing the heat-ambulance association, we recommend that (1) using data on spatially refined gridded temperature that is either very well interpolated or derived from satellite imaging may be an alternative to reduce exposure measurement bias; and (2) linking ambulance data with hospital admission data can be useful to improve health outcome classification.

Extreme Temperature Exposure and Risks of Preterm Birth Subtypes Based on a Nationwide Survey in China

BACKGROUND

Previous studies have reported that ambient temperature may affect perinatal outcomes. However, whether extreme temperature affects the risk of preterm birth (PTB) remains controversial. Studies on the associations of extreme temperature with PTB subtypes are lacking.

OBJECTIVES

We aimed to investigate the associations of extreme climate events with the risks of PTB and its subtypes, discerning possible modifiers.

METHODS

Data on all singleton deliveries were obtained from the China Labor and Delivery Survey (CLDS), a nationwide investigation implemented in 2015 and 2016. PTB was defined as gestational weeks < 37 and then categorized as early (24-34 wk) and late PTBs (35-36 wk), and clinical subtypes [spontaneous PTB, preterm premature rupture of the fetal membranes (PPROM), iatrogenic PTB]. Ambient temperature data were provided by the China National Weather Data Sharing System. Five heat indexes and five cold indexes were used to define heat waves and cold spells. Generalized linear mixed models with a random term by hospital unit were used to assess the associations of short-term prenatal extreme temperature exposure. The Cox proportional hazard regression model was applied to assess the nonlinear associations of low- or high-temperature exposure at the whole and different trimesters of pregnancy with the risk of PTB. Stratified analyses were conducted to assess the possible modification by geographic region and fetal sex.

RESULTS

A total of 70,818 singleton births from 96 hospitals in China were included, among which 4,965 (7.01%) were PTBs. Exposure to extreme cold events 1 wk before delivery was associated with an increased PTB risk, with an adjusted odds ratio (aOR) [95% confidence intervals (CIs)] of 1.07 (95% CI: 1.04, 1.10) and 1.06 (1.04, 1.09) for the total days when the daily average temperature below the fifth percentile (fifth-days) and the 10th percentile (10th-days), 1.18 (1.04, 1.34) for the cold spells when the daily average temperature below the fifth percentile for two consecutive days (fifth-2D), 1.09 (1.03, 1.16) and 1.12 (1.06, 1.19) for the cold spells when the daily average temperature below the 10th percentile for three and two consecutive days (10th-3D and 10th-2D), respectively. Results of extreme temperature exposure during 2 weeks before delivery showed similarly significant associations. The association between cold spells and PTB tended to be stronger for late PTB than for early PTB. Cold spells were mainly associated with spontaneous PTB and late PPROM. A stratified analysis indicated that pregnant women in western and northern regions tended to be more sensitive to cold spells, and pregnant women with a female fetus appeared to be at a higher risk of PTB when exposed to cold spells. Pregnant women in late pregnancy were more susceptible to extreme temperatures. No significant or stable association was found between heat waves and preterm birth.

DISCUSSION

Exposure to cold spells was associated with an increased risk of PTB, especially late, spontaneous PTB and PPROM. The associations appeared to be more pronounced in the north and west regions and in pregnancies with female fetuses. https://doi.org/10.1289/EHP10831.

The impact of non-optimum temperatures, heatwaves and cold spells on out-of-hospital cardiac arrest onset in a changing climate in China: a multi-center, time-stratified, case-crossover study

Background

Out-of-hospital cardiac arrest (OHCA) is a time-critical and fatal medical emergency that has been linked to non-optimal temperatures. However, the future burden of OHCA due to non-optimal temperatures, heatwaves, and cold spells under climate change has not been well evaluated.

Methods

We conducted a time-stratified case-crossover study in 15 Northern Chinese cities throughout 2020 to estimate the exposure-response relationships of non-optimal temperatures, heatwaves, and cold spells with hourly OHCA onset in hot and cold seasons. We obtained future daily average temperatures by using 20 general circulation models under two greenhouse gas emission scenarios: one with certain emission control and the other with relaxed control. Lastly, we projected the change of OHCA burden under these two climate scenarios.

Findings

We analyzed a total of 29,671 OHCA patients and found that high temperatures and heatwaves as well as low temperatures and cold spells were all significantly associated with an increased risk of OHCA onset. Under the scenario of uncontrolled emissions, the attributable fraction (AF) of OHCA due to high temperatures and heatwaves would increase by 4.94% and 6.99% from the 2010s to 2090s, respectively. The AF due to low temperatures would decrease by 1.27% by the 2090s and the effects of cold spells were projected to be marginal after the 2050s. Under a medium emission control scenario, the upward trend of heat-related OHCA burden would become flat, and the decline in cold-related OHCA burden would also slow down.

Interpretation

Our study provides evidence of significant morbidity risk and burden of OHCA associated with global warming across Northern China. Our findings indicate that the increase in OHCA burden attributable to heat could not be offset by the decrements attributable to cold, emphasizing the importance of mitigation policies for limiting global warming and reducing the associated risks of OHCA onset.

Funding

National Science & Technology Fundamental Resources Investigation Project (2018FY100600, 2018FY100602), National Key R&D Program of China (2020YFC1512700, 2020YFC1512705, 2020YFC1512703), Key R&D Program of Shandong Province (2021ZLGX02, 2021SFGC0503), Natural Science Foundation of Shandong Province (ZR2021MH231), Taishan Pandeng Scholar Program of Shandong Province (tspd20181220), the Interdisciplinary Young Researcher Groups Program of Shandong University (2020QNQT004), ECCM Program of Clinical Research Center of Shandong University (2021SDUCRCA001, 2021SDUCRCA002), foundation from Clinical Research Center of Shandong University (2020SDUCRCB003), National Natural Science Foundation of China (82272240).

The joint and interaction effect of high temperature and humidity on mortality in China

BACKGROUND

Although many studies have reported the mortality effect of temperature, there were few studies on the mortality risk of humidity, let alone the joint effect of temperature and humidity. This study aimed to investigate the joint and interaction effect of high temperature and relative humidity on mortality in China, which will deepen understanding the health risk of mixture climate exposure.

METHODS

The mortality and meteorological data were collected from 353 locations in China (2013-2017 in Jilin, Hunan, Guangdong and Yunnan provinces, 2009-2017 in Zhejiang province, and 2006-2011 in other Provinces). We defined location-specific daily mean temperature ≥ 75th percentile of distribution as high temperature, while minimum mortality relative humidity as the threshold of high relative humidity. A time-series model with a distributed lag non-linear model was first employed to estimate the location-specific associations between humid-hot events and mortality, then we conducted meta-analysis to pool the mortality effect of humid-hot events. Finally, an additive interaction model was used to examine the interactive effect between high temperature and relative humidity.

RESULTS

The excess rate (ER) of non-accidental mortality attributed to dry-hot events was 10.18% (95% confidence interval (CI): 8.93%, 11.45%), which was higher than that of wet-hot events (ER = 3.21%, 95% CI: 0.59%, 5.89%). The attributable fraction (AF) of mortality attributed to dry-hot events was 10.00% (95% CI: 9.50%, 10.72%) with higher burden for females, older people, central China, cardiovascular diseases and urban city. While for wet-hot events, AF was much lower (3.31%, 95% CI: 2.60%, 4.30%). We also found that high temperature and low relative humidity had synergistic additive interaction on mortality risk.

CONCLUSION

Dry-hot events may have a higher risk of mortality than wet-hot events, and the joint effect of high temperature and low relative humidity may be greater than the sum of their individual effects.

Increased emergency cases for out-of-hospital cardiac arrest due to cold spells in Shenzhen, China

Cold spells have been associated with specific diseases. However, there is insufficient scientific evidence on the effects of cold spells on out-of-hospital cardiac arrest (OHCA). Data on OHCA cases and on meteorological factors and air pollutants were collected between 2013 and 2020. We adopted a quasi-Poisson generalized additive model with a distributed lag nonlinear model (DLNM) to estimate the effect of cold spells on daily OHCA incidence. Backward attributable risk within the DLNM framework was calculated to quantify the disease burden. We compared the effects and OHCA burden of cold spells using nine definitions. The risks of different cold spells on OHCA increased at higher intensities and longer durations. Based on Akaike's information criterion for the quasi-Poisson regression model and the attributable risk, the optimal cold spell was defined as a period in the cold month when the daily mean temperature was below the 10th percentile of the temperature distribution in the study period for at least 2 days. The single-day effect of the optimal cold spell on OHCA occurred immediately and lasted for approximately 1 week. The maximum single-day effect was 1.052 (95% CI: 1.018-1.087) at lag0, while the maximum cumulative effect was 1.433 (95% CI:1.148-1.788) after a 14-day lag. Men were more susceptible to cold spells. Young and middle-aged people were affected by cold spells similar to the elderly. Cold spells can increase the risk of OHCA with an approximately 1-week lag effect. Health regulators should take more targeted measures to protect susceptible populations during cold weather.

Impact of extreme weather on dengue fever infection in four Asian countries: A modelling analysis

The rapid spread of dengue fever (DF) infection has posed severe threats to global health. Environmental factors, such as weather conditions, are believed to regulate DF spread. While previous research reported inconsistent change of DF risk with varying weather conditions, few of them evaluated the impact of extreme weather conditions on DF infection risk. This study aims to examine the short-term associations between extreme temperatures, extreme rainfall, and DF infection risk in South and Southeast Asia. A total of 35 locations in Singapore, Malaysia, Sri Lanka, and Thailand were included, and weekly DF data, as well as the daily meteorological data from 2012 to 2020 were collected. A two-stage meta-analysis was used to estimate the overall effect of extreme weather conditions on the DF infection risk. Location-specific associations were obtained by the distributed lag nonlinear models. The DF infection risk appeared to increase within 1-3 weeks after extremely high temperature (e.g. lag week 2: RR = 1.074, 95 % CI: 1.022-1.129, p = 0.005). Compared with no rainfall, extreme rainfall was associated with a declined DF risk (RR = 0.748, 95 % CI: 0.620-0.903, p = 0.003), and most of the impact was across 0-3 weeks lag. In addition, the DF risk was found to be associated with more intensive extreme weathers (e.g. seven extreme rainfall days per week: RR = 0.338, 95 % CI: 0.120-0.947, p = 0.039). This study provides more evidence in support of the impact of extreme weather conditions on DF infection and suggests better preparation of DF control measures according to climate change.

The interplay between bystander cardiopulmonary resuscitation and ambient temperature on neurological outcome after cardiac arrest: A nationwide observational cohort study

BACKGROUND

At lower ambient temperature, patients with out-of-hospital cardiac arrest (OHCA) easily experience hypothermia. Hypothermia has shown to improve the rate of successful return of spontaneous circulation (ROSC) in animal models. We hypothesized that lower temperature affects the impact of bystander cardiopulmonary resuscitation (CPR) on the increased odds of a favorable neurological outcome post-OHCA.

METHODS

This study used information collected by the prospective, nationwide, Utstein registry to examine data from 352,689 adult patients who experienced OHCA from 2012 to 2016 in Japan. The primary outcome was a 1-month favorable neurological outcomes. Multivariable logistic regression analyses were conducted to test the impact of bystander CPR according to the temperature on the favorable outcome.

RESULTS

A total of 201,111 patients with OHCA were included in the complete case analysis. The lower temperature group had lower proportions of receiving bystander CPR (46.5 vs. 47.9%) and having favorable outcome (2.1 vs 2.8%) than those in the higher group. Multivariable analysis revealed that bystander CPR at lower temperatures was significantly associated with favorable outcomes (adjusted odds ratio, 1.22; 95% CI, 1.09-1.37), whereas bystander CPR at higher temperatures was not associated with favorable outcomes (1.02; 0.92-1.13). The nonlinear relationship using a spline curve in the multivariable model revealed that odds ratio of favorable neurological outcomes associated with bystander CPR increased as the temperature decreased.

CONCLUSION

Bystander CPR was associated with favorable neurological outcomes at lower temperatures. The odds of a favorable outcome associated with bystander CPR increased as the temperature decreased.