Cardiorespiratory effects of heatwaves: A systematic review and meta-analysis of global epidemiological evidence

BACKGROUND

Heatwaves affect human health and global heatwave-related disease burden will continue to rise as climate change proceeds, but the effects of heatwaves on cardiovascular and respiratory diseases have not yet been investigated globally and nationally.

OBJECTIVES

This systematic review and meta-analysis aim to quantify heatwave effects on four major health outcomes: cardiovascular and respiratory morbidity and mortality.

METHODS

We searched PubMed, Scopus, Embase, and Web of Science for relevant studies from database inception to November 2018. Categories of morbidity included hospital admissions, emergency department visits, and ambulance attendances/call-outs. A random-effects meta-analysis model was used to pool previous estimates of heatwave effects on mortality and morbidity due to cardiovascular and respiratory diseases. Subgroup analyses by gender, age, and disease cause were conducted. Sensitivity analyses were performed by the categories of morbidity, heatwave definitions, study design, and using a leave-one-out cross validation approach. This study is registered with PROSPERO (number: CRD42018101964).

RESULTS

We identified 54 studies conducted in 20 countries. In total, there were significant associations between heatwaves and cardiovascular mortality (risk estimates (RE): 1.149, 95% confidence interval (CI): 1.090, 1.210) and respiratory mortality (RE: 1.183, 95%CI: 1.092, 1.282), but the magnitude of these associations varied across countries and studies. Heatwaves appeared to be marginally associated with cardiovascular and respiratory morbidities (RE: 0.999, 95%CI: 0.996, 1.002, p-value = 0.61 for cardiovascular morbidity; RE: 1.043, 95%CI: 0.995, 1.093; p-value = 0.08 for respiratory morbidity). For mortality, significant associations were observed for the elderly, ischemic heart disease, stroke, heart failure, and chronic obstructive pulmonary disease. Sensitivity analyses suggested that these findings were robust.

CONCLUSION

Mortality of cardiovascular and respiratory diseases appeared to be more vulnerable to heatwaves in comparison to morbidity. Considering high heterogeneity detected between studies and limited investigations into subpopulations, more research are required to provide a clearer picture of how heatwaves affect cardiovascular and respiratory diseases in different settings.

[Estimation of heat-related deaths in Germany between 2001 and 2015]

BACKGROUND

During the summers of 2003 and 2015, heat was found to be the cause of a substantial number of deaths in Germany. Until now, estimates for the total number of heat-related deaths were only available regionally in Germany. For the summer of 2003, an analysis for Baden-Württemberg was extrapolated to the whole of Germany.

OBJECTIVES

Our analysis tries to prove a stable statistical relationship between heat and mortality and to use this to quantify the number of heat-related deaths in Germany between the years 2001 and 2015.

MATERIALS AND METHODS

By fitting a nonlinear statistical model, we estimated exposure-response curves that describe the influence of heat on the mortality rate. The performance of different indicators for heat stress was compared.

RESULTS

The comparison of the different indicators for heat showed that the weekly mean temperature was most useful to explain the course of the weekly mortality during the summer. The relation between mortality rate and weekly mean temperature varied between age groups and regions in Germany (north, middle, south). The age groups (75-84) and (85+) were most affected by heat. The highest number of heat-related deaths was 7600 (95% CI 5500-9900), found for the summer 2003, followed by 6200 (4000; 8000) in the summer 2006 and 6100 (4000; 8300) in the summer 2015.

CONCLUSIONS

We could show that even in weekly data on mortality, a clear influence of heat could be identified. A national surveillance of mortality that allows real-time monitoring would be desirable.

Joint effects of heatwaves and air quality on ambulance services for vulnerable populations in Perth, western Australia

As the frequency, intensity, and duration of heatwaves increases, emergency health serviceutilization, including ambulance service, has correspondingly increased across the world. The negative effects of air pollution on health complicate these adverse health effects. This research work is the first known study to analyze the joint effects of heatwaves and air quality on the ambulance service in Western Australia (WA). The main objective is to investigate the potential joint effects of heatwaves and air quality on the ambulance service for vulnerable populations in the Perth metropolitan area. A time series design was used. Daily data on ambulance callouts, temperature and air pollutants (CO, SO₂, NO₂, O₃, PM₁₀ and PM_2.5) were collected for the Perth metropolitan area, WA from 2006 to 2015. Poisson regression modeling was used to assess the association between heatwaves, air quality, and ambulance callouts. Risk assessments on age, gender, socio-economic status (SES), and joint effects between heatwaves and air quality on ambulance callouts were conducted. The ambulance callout rate was higher during heatwave days (14.20/100,000/day) compared to non-heatwave days (13.95/100,000/day) with a rate ratio of 1.017 (95% confidence interval 1.012, 1.023). The ambulance callout rate was higher in males, people over 60 years old, people with low SES, and those living in coastal areas during period of heatwaves. Exposure to CO, SO₂, O₃ and PM_2.5 increased risk on ambulance callouts and exposure to NO₂ showed joint effect with heatwave and increased risk of ambulance callouts by 3% after adjustment of all other risk factors. Ambulance callouts are an important indicator for evaluating heatwave-related emergency morbidity in WA. As the median concentrations of air pollutants in WA were lower than the Australian National Standards, the interactive effects of heatwaves and air quality on ambulance service need to be further examined, especially when air pollutants exceed the standards.

Growth and photosynthetic responses in Brassica napus differ during stress and recovery periods when exposed to combined heat, drought and elevated CO2

This study was intended to investigate how an agronomically important crop Brassica napus will be able to cope with the combined impact of a heatwave (21/14 °C vs. 33/26 °C day/night) and drought under ambient or elevated CO₂ (800 vs. 400 μmol mol^-1) and to what degree their recovery will be ensured after the stress, when additional CO₂ is also removed. The obtained results revealed that, in the presence of an adequate water supply, B. napus performed well under heatwave conditions. However, drought fully negated all the advantages gained from hotter climate and led to a slower and incomplete recovery of gas exchange and retarded growth after the stress, regardless mitigating the effect of elevated CO₂ during the stress. The mechanism by which the elevated CO₂ diminished the adverse effect of a combined heat and drought stress on photosynthetic rate at saturating light (A_sat) was attributed to the improved plant water relations. However, it had little effect on the recovery of A_sat. In contrast, the mechanism by which photosynthesis was more impaired under the combination of heatwave and drought, compared to single drought treatment, was attributed mainly to the faster soil drying as well as faster and sharper decrease in stomatal conductance and subsequent in C_i/C_a. Keeping in mind that photosynthesis can acclimatize by downregulation to higher CO₂, the results of this study, showing a weak memory of mitigating the effect of elevated CO₂, highlight a potential risk of more intense and frequent heatwaves and droughts on B. napus.

Impact of the warm summer 2015 on emergency hospital admissions in Switzerland

BACKGROUND

Only a few studies have examined the impact of a particular heat event on morbidity. The aim of this study was to evaluate the impact of the warm summer 2015 on emergency hospital admissions (EHA) in Switzerland. The summer 2015 ranks as the second hottest after 2003 in the history of temperature observation in Switzerland.

METHODS

Daily counts of EHA for various disease categories during summer 2015 were analyzed in relation to previous summers in Switzerland. Excess EHA for non-external causes during summer 2015 (June-August) were estimated by age group, gender, geographic region and disease category by comparing observed and expected cases. The latter were predicted from strata-specific quasi-Poisson regression models fitted to the daily counts of EHA for years 2012-2014.

RESULTS

Over the three summer months in 2015, an estimated 2.4% (95% confidence interval [CI] 1.6-3.2%) increase in EHA (non-external causes) occurred corresponding to 2,768 excess cases. Highest excess EHA estimates were found in the warmest regions (Ticino [8.4%, 95% CI 5.1-11.7%] and the Lake Geneva region [4.8%, 95% CI 3.0-6.7%]) and among the elderly population aged ≥75 years (5.1%, 95% CI 3.7-6.5%). Increased EHA during days with most extreme temperatures were observed for influenza and pneumonia, certain infectious diseases and diseases of the genitourinary system.

CONCLUSIONS

Summer 2015 had a considerable impact on EHA in Switzerland. The daily number of EHA mainly increased due to diseases not commonly linked to heat-related mortality. No excess morbidity was found for cardiovascular and most respiratory diseases. This suggests that current public health interventions should be reevaluated to prevent both heat-related illness and deaths.

Joint effect of heatwaves and air quality on emergency department attendances for vulnerable population in Perth, Western Australia, 2006 to 2015

BACKGROUND

As global warming and the frequency and intensity of heatwaves increases, health service utilization, including emergency department attendances (EDA) have correspondingly increased across the world. The impact of air quality on health adds to the complexity of the effects. Potential joint effects between heatwaves and air quality on EDA have been rarely reported in the literature, prompting this study.

OBJECTIVES

To investigate the potential joint effect of heatwaves and air quality on the EDA for vulnerable populations in the Perth metropolitan area, Western Australia.

METHODS

A time series design was used. Daily data on EDA, heatwaves (excess heat factor>0) and air pollutants (CO, SO₂, NO₂, O₃, PM₁₀ and PM_2.5) were collected for Perth, Western Australia from 2006 to 2015. Poisson regression modelling was used to assess the associations between heatwaves, air quality, and EDA. Risk assessments on age, gender, Aboriginality, socio-economic status (SES), and joint effect between heatwaves and air quality on EDA were conducted.

RESULTS

The EDA rate was higher in heatwave days (77.86/100,000/day) compared with non-heatwave days (73.90/100,000/day) with rate ratio of 1.053 (95% confidence interval 1.048, 1.058). The EDA rate was higher in males, people older than 60 years or younger than 15 years, Aboriginal people, and people with low SES. Exposure to CO, SO₂, O₃ and PM_2.5 increased risk on EDA and exposure to PM_2.5 showed joint effect with heatwave and increased risk of EDA by 6.6% after adjustment of all other risk factors.

CONCLUSIONS

EDA is an important indicator to evaluate heatwave related morbidity for emergency medical service as EDA rate increased during heatwaves with relative high concentrations of air pollutants. As all air pollutants measured in the study were lower than the Australian National Standards, the joint effect of heatwaves and air quality needs to be further examined when it exceeds the standards.

Heatwaves and hospitalizations due to hyperthermia in defined climate regions in the conterminous USA

Heatwaves are one of the deadliest natural disasters that occur annually with thousands of people seeking medical attention. The spatio-temporal synchronization between peaks in disease manifestation and high temperature provides important insights into the seasonal timing of the heatwave and the response it may cause with respect to emergence, severity, and duration. The objectives of this study are to examine the association between hospitalizations due to heat stroke in older adults and heat in the United States (US) and explore synchronization with respect to heatwave sequence, time of arrival, and regional climate. Three large data sets were utilized: daily hospitalization records of the US elderly between 1991 and 2006, annual demographic summaries on Medicare beneficiaries maintained by the Centers for Medicare and Medicaid Services (CMS), and nationwide daily meteorological observations. We modeled seasonal fluctuations in health outcomes, such as the timing and intensity of the seasonal peak in hospitalizations using refined harmonic GLM for eight climatically similar regions. During the 16-year study period, there were 40,019 heat-related hospitalizations (HRH) in the conterminous  US. The rates of HRH varied substantially across eight climatic regions: with the highest rate of 7.05 cases per million residents observed in areas with temperate arid summers and winters (TaTa) and the lowest rate of 0.67-in areas with cold moderately dry summers and arid winters (CdCa), where summer temperatures are about  18.3 °C and 12.1 °C, respectively. We detected 400 heatwaves defined as any day when the night time temperature is above its 90th percentile for the current and previous nights. The first seasonal heatwave in a season resulted in 4274 hospitalizations over 342 heatwave-days: 34.3% of 12,442 hospitalizations occurred in 26% of 1308 heatwave-days. The relative risks of increased HRH associated with the first and second heatwaves were 10.4 (95%CI: 8.5; 12.3) and 11.4 (95%CI: 9.6; 13.3), respectively, indicating the disproportional effects of early heatwave arrivals. The seasonal spike in heat stroke hospitalizations in regions with relatively similar annual temperatures, e.g. in areas with temperate moderately dry summers and winters (TdTa: 12.8 °C) and (TaTa: 11.1 °C) ranged between 4.5 (95%CI: 3.3; 5.5) and 11.0 (95%CI: 8.2; 14.9) cases per million residents, respectively, indicating substantial regional differences. The differences in heat-related hospitalizations and response to heatwaves are substantial among older adults residing in different climate regions of the conterminous US. The disproportionally high response to the early seasonal heatwave deserves special attention, especially in the context of prevention and decision support frameworks.

Potential benefits of cool roofs in reducing heat-related mortality during heatwaves in a European city

Hot weather can exacerbate health conditions such as cardiovascular and respiratory diseases, and lead to heat stroke and death. In built up areas, temperatures are commonly observed to be higher than those in surrounding rural areas, due to the Urban Heat Island (UHI) effect. Climate change and increasing urbanisation mean that future populations are likely to be at increased risk of overheating in cities, although building and city scale interventions have the potential to reduce this risk. We use a regional weather model to assess the potential effect of one type of urban intervention - reflective 'cool' roofs - to reduce local ambient temperatures, and the subsequent impact on heat-related mortality in the West Midlands, UK, with analysis undertaken for the summer of 2006, as well as two shorter heatwave periods in 2006 and 2003. We show that over a summer season, the population-weighted UHI intensity (the difference between simulated urban and rural temperature) was 1.1 °C on average, but 1.8 °C when including only night times, and reached a maximum of 9 °C in the West Midlands. Our results suggest that the UHI contributes up to 40% of heat related mortality over the summer period and that cool roofs implemented across the whole city could potentially offset 18% of seasonal heat-related mortality associated with the UHI (corresponding to 7% of total heat-related mortality). For heatwave periods, our modelling suggests that cool roofs could reduce city centre daytime 2 m air temperature by 0.5 °C on average, and up to a maximum of ~3 °C. Cool roofs reduced average UHI intensity by ~23%, and reduced heat related mortality associated with the UHI by ~25% during a heatwave. Cool roofs were most effective at reducing peak temperatures during the daytime, and therefore have the potential to limit dangerous extreme temperatures during heatwaves. Temperature reductions were dependent on the category of buildings where cool roofs were applied; targeting only commercial and industrial type buildings contributed more than half of the reduction for heatwave periods. Our modelling suggested that modifying half of all industrial/commercial urban buildings could have the same impact as modifying all high-intensity residential buildings in the West Midlands.

What do we know about the healthcare costs of extreme heat exposure? A comprehensive literature review

Exposure to extreme heat can lead to a range of heat-related illnesses, exacerbate pre-existing health conditions and cause increased demand on the healthcare system. A projected increase in temperature may lead to greater healthcare expenditure, however, at present the costs of heat-related healthcare utilization is under-researched. This study aims to review the literature on heat-related costs for the healthcare system with a focus on ED visits, hospitalization, and ambulance call-outs. PubMed, Scopus, and Embase were used to search relevant literature from database inception to December 2017 and limited to human studies and English language. After screening, a total of ten papers were identified for final inclusion. In general, the healthcare costs of heat extremes have been poorly investigated in developed countries and not reported in developing countries where the largest heat-vulnerable populations reside. Studies showed that exposure to extreme heat was causing a substantial economic burden on healthcare systems. Females, the elderly, low-income families, and ethnic minorities had the highest healthcare costs on a range of health services utilization. Although a few studies have estimated heat healthcare costs, none of them quantified the temperature-healthcare cost relationship. There is a need to systematically examine heat-attributable costs for the healthcare system in the context of climate change to better inform heat-related policy making, target interventions and resource allocation.

A random forest model to predict heatstroke occurrence for heatwave in China

Extreme heat events have recently become more frequent and represent an increasing risk of damage to public health. However, the existing prediction of heatwave related health effects has limited representativeness and verification. Our study addressed the prediction of heatstroke occurrences based on three years' data of typical cities of hot temperature in China, and examined the importance ranks of model parameters including meteorological and socioeconomic status (SES) factors. The results show that meteorological factors contributed the most to model estimation of the parameters evaluated, and SES parameters, such as the search index, were also important indicators of heatstroke prediction. The model had a satisfying performance compared to traditional linear regression models. The model established in our study can be further applied to extreme weather-related impact research and reduce economic loss due to public health expenses.

Impact of heatwaves on daily outpatient visits of respiratory disease: A time-stratified case-crossover study

OBJECTIVES

This study aims to estimate the impact of heatwaves from July 2010 to October 2012 on daily outpatient visits for respiratory disease (RD) in Cangnan, China and identify vulnerable populations.

METHODS

The definition of heatwave was a period at least 3 consecutive days with maximum temperature exceeding 35 °C in this study. A time-stratified case-crossover design was conducted to examine the relationship between heatwaves and outpatient visits for RD. Patient data for the period from 2010 to 2012 were collected from the Third People's Hospital of Cangnan and daily meteorological data for the same period were collected from the China Meteorological Data Service Center. Data regarding the air pollution index (API), a composite indicator of air pollution, were collected from the Data Center of the Chinese Ministry of Environmental Protection. RD were identified based on the 10th revision International Classification of Diseases (ICD-10) codes (J00-J99). A conditional Poisson regression model was applied to examine the heatwave-RD association using the Relative Risk (RR) while adjusting for meteorological and air pollution factors including temperature, rainfall, wind speed, pressure, humidity, sunshine hours and API.

RESULTS

During the study period, 4 heatwaves occurred and a total of 1732 outpatient visits for RD were reported. Heatwaves increased the frequency of RD outpatient visits and the highest RR of total RD was 1.155% and 95% Confidence Intervals (95% CI) was 1.084-1.232 at Lag 0. For subcategories, heatwaves increased the risk of infectious RD (Lag 0: RR =1.182, 95% CI: 1.106-1.263) and decreased the risk of non-infectious RD ((Lag 6: RR =0.750, 95% CI: 0.568-0.990). Moreover, heatwaves showed adverse effects on acute upper respiratory infection (Lag 0: RR =1.306, 95% CI: 1.177-1.450). The RR of outpatient visits for RD was statistically significant in females (Lag 0: RR =1.161, 95% CI: 1.046-1.298), males (Lag 4: RR =1.161, 95% CI: 1.096-1.261), young people aged 4-17 years (Lag 0: RR =1.741, 95% CI: 1.524-1.990) and elders aged 65 years or older (Lag 5: RR =1.412, 95% CI: 1.111-1.794) during heatwaves.

CONCLUSIONS

Heatwaves had a significant harmful impact on daily outpatient visits for RD in Cangnan, especially for vulnerable population identified. These results can be used not only to strengthen the health education and protection of these vulnerable populations, but also to assist relevant organizations with developing intervention programmes and improving disease prevention and community care.

Heatwave and mortality in 31 major Chinese cities: Definition, vulnerability and implications

Few data are available on the health impacts of heatwaves in China, and in particular, the heatwave definition and vulnerable populations remain to be identified. We collected data on daily maximum temperature and mortality from 31 Chinese capital cities during 2007-2013. A Poisson regression model allowing for over-dispersion was applied to estimate the short-term effects of heatwaves on mortality in hot season (May-September). 15 heatwave definitions combining five heat thresholds (90.0th, 92.5th, 95th, 97.5th and 99th percentiles of daily maximum temperature) and three durations (≥2, ≥3 and ≥4 days) were compared. The pooled effects were then computed using random effect meta-analysis based on the residual maximum likelihood estimation. Effect modification of heatwave-mortality association by individual-level characteristics was tested using a stratified analysis. Potential effect modification by city-level characteristics was examined by meta-regression analysis. Totally, 259 million permanent residents were covered and 4,481,090 non-accidental deaths occurred during the study period. Generally, the magnitude of heatwave impacts increased by intensities and durations of the heatwaves. Heatwave definition using daily maximum temperature ≥ 92.5th percentile with duration ≥3 days produced the best model fit. The pooled relative risks of heatwaves on non-accidental mortality at lag 0, lag 0-2 and lag 0-10 days were 1.06 (95%CI: 1.03-1.09), 1.09 (1.05-1.13) and 1.10 (1.05-1.15), respectively. Compared with non-accidental mortality, higher effect estimates of heatwaves were observed among deaths from ischemic heart diseases, stroke and respiratory diseases, although the differences were not statistically significant. Females, those ≥75 years old and the illiterates were more vulnerable to heatwaves. Cities with higher concentrations of PM_2.5, higher latitudes, and lower numbers of hospital beds per 10,000 populations had higher mortality risks during heatwaves. These findings may have important implications for developing heat alert systems and early response actions on protecting the vulnerable populations from adverse health effects of heatwave in China.

Emergency department asthma diagnosis risk associated with the 2012 heat wave and drought in Douglas County NE, USA

BACKGROUND

Global climate change concerns are forcing local public health agencies to assess potential disease risk.

OBJECTIVE

Determine if risk of an emergency department asthma diagnosis in Douglas County, NE, was higher during the 2012 heatwave compared to 2011.

METHODS

Retrospective, observational, case-control design selecting subjects from 2011 and 2012 emergency department (ED) admissions. Risk was estimated by conditional logistic regression.

RESULTS

The asthma ED risk estimate was 1.23 (95%CI = 0.96-1.57) times higher in 2012 than 2011, for the same calendar period. Asthma ED diagnosis risk was 3.37 (95%CI = 2.27-4.17) times higher among subjects <19years old compared to older subjects, and 3.25 (95%CI = 2.63-4.02) times higher among African-Americans than non-African-Americans, adjusted for heatwave exposure. Absolute humidity appears inversely related to asthma diagnosis risk ( χ2 = 16.6; p < 0.001).

CONCLUSION

Asthma ED diagnosis risk was not significantly higher in 2012 compared to 2011. Risk was elevated among subjects less than 19years old, and among African Americans; adjusted for heatwave exposure.

Intermittent wetting clothing as a cooling strategy for body heat strain alleviation of vulnerable populations during a severe heatwave incident

Many documented studies have demonstrated the human mortality rate increases during severe heatwaves. There remains a need for further explore ecologically valid cooling strategies to alleviate body heat strain during extreme heatwaves. The main aim of this work was to explore whether intermittent wetting clothing can be served as an ecologically valid cooling strategy to mitigate heat stress on inactive vulnerable populations not having access to air-conditioning during a severe heatwave. Ten young male subjects underwent two 90-min separate trials: a dry clothing trial (i.e., CON) and a wetted clothing cooling trial (i.e., WEC). A set of light summer wear was chosen and intermittently wetted by tap water at intervals of every 30 min. Physiological and perceptual responses of subjects were examined and compared. All trials were performed in a chamber with an air temperature of 43 ± 0.5 °C, RH= 57 ± 5% and an air velocity of 0.15 ± 0.05 m/s (WBGT=37.35 °C). Results demonstrated that WEC, compared with CON, could significantly reduce both the mean skin temperature and the core temperature throughout the 5-90th min and 25-90th min of the trial, respectively (p < 0.05). Besides, WEC could also remarkable reduce local skin temperatures at those body sites covered by wet clothing (p < 0.05). In comparison, no significant difference was found between WEC and CON on perceptual responses. Further, it was also found from PHS simulations that conditions with a partial water vapour pressure ≤ 3.1-3.5 kPa would not induce pronounced core temperature rises at 43 °C. Finally, it may be concluded that intermittent wetting clothing could be served as an ecologically valid cooling strategy to reduce thermophysiological strain of vulnerable populations while seating during humid heatwaves and thereby improve their health and safety.

Assessing heatwave impacts on cause-specific emergency department visits in urban and rural communities of Queensland, Australia

BACKGROUND

Heatwave impact on morbidity of people in rural areas has rarely been assessed in prior studies, and recently published literature has documented heatwave impact on a wide spectrum of diseases, for example, ear and eye diseases.

OBJECTIVES

To examine the associations between heatwaves and cause-specific emergency department visits (EDVs) across eight communities in both urban and rural regions throughout Queensland, Australia.

METHODS

Daily data on EDVs, air pollution and climatic conditions during the 1st January 2013 to the 31st December 2015 were obtained from relevant government agencies. Heatwave was defined as ≥ 95th percentile of the mean temperature for three or more consecutive days in each community. A quasi-Poisson generalized additive model with a distributed lag non-linear model was used to assess the heatwave impacts on EDVs. Random effect meta-analysis was performed to investigate the effects of heatwaves on cause-specific EDVs across the urban and rural regions as well as the whole Queensland. The causes of EDVs investigated in this study were infectious and parasitic diseases (ICD code: A00-B99), endocrine, nutritional and metabolic diseases (E00-E90), mental and behavioural disorders (F00-F99), diseases of the nervous system (G00-G99), diseases of the ear and mastoid process (H60-H95), diseases of the circulatory system (I00-I99), diseases of the respiratory system (J00-J99), diseases of the skin and subcutaneous tissue (L00-L99), diseases of the musculoskeletal system and connective tissue (M00-M99), diseases of the genitourinary system (N00-N99), and injury, poisoning and certain other consequences of external causes (S00-T98).

RESULTS

The meta-analysis results showed that there were significant effects of heatwaves on total EDVs and a wide-spectrum of cause-specific EDVs. For example, EDVs for endocrine, nutritional and metabolic diseases (RR: 1.18, 95% CI: 1.04-1.34), diseases of the nervous system (RR: 1.09, 95% CI: 1.02-1.17), and diseases of the genitourinary system (RR: 1.05, 95% CI: 1.00-1.09) increased substantially during heatwave days. The effect of heatwaves on total EDVs was similar for rural (RR: 1.04, 95% CI: 1.01-1.07) and urban regions (RR: 1.04, 95% CI: 1.00-1.07).

CONCLUSIONS

A wide range of diseases were sensitive to heatwave impacts. Residents in urban and rural areas were all vulnerable to heatwave impacts, calling for heat adaptation measures to be undertaken in Queensland, Australia.

Mortality burden attributable to heatwaves in Thailand: A systematic assessment incorporating evidence-based lag structure

BACKGROUND

Available information on the acute and cumulative effects of heatwaves on cause-specific mortality in Thailand is scarce.

OBJECTIVES

To quantify the acute and cumulative effects of heatwaves on mortality in Thailand, and assess heatwave-related mortality burden.

METHODS

Thirty heatwave definitions were used and categorized into three groups: low intensity heatwaves (HW_low), middle intensity heatwaves (HW_middle), and high intensity heatwaves (HW_high). Time-series analyses were conducted to examine the acute and cumulative effects of HW_low, HW_middle, and HW_high on total and cause-specific mortality in 60 provinces of Thailand, incorporating an optimal lag for each cause and each province. Random-effects meta-analyses were performed to pool provincial estimates to national estimates for both acute and cumulative effects. Meta-regressions were conducted to identify the possible factors contributing to the spatial heterogeneity of heatwave vulnerability.

RESULTS

The cumulative effects of HW_low and HW_middle on total and cause-specific mortality were greater than HW_high. Both acute and cumulative effects of HW_low, HW_middle and HW_high on neoplasms and certain infectious and parasitic diseases were among the highest across all death causes. Effects of heatwaves on deaths from endocrine, nutritional and metabolic diseases appeared to be longer-lasting, and effects of heatwaves on deaths from ischaemic heart diseases and pneumonia occurred more rapidly. Northern and Central Thailand were the regions vulnerable to heatwaves, and proportion of elderly population was the major driver behind the spatial heterogeneity of heatwave vulnerability.

CONCLUSIONS

More attention needs to be paid to mild heatwaves. Future heatwave-related mortality burden due to neoplasms and infectious diseases in Thailand may increase as climate change continues.

Regional morbidity and mortality during heatwaves in South Australia

Heatwaves can be a common occurrence in Australia, and the public health impacts can be severe. Heat warnings and interventions are being adopted widely to reduce the preventable health impacts. This study examines the effects of heatwaves on morbidity and mortality in different climatic regions in the state of South Australia, to inform the targeting of heat warnings according to regional needs. Heatwaves were defined using the excess heat factor (EHF), an index based on mean daily temperature indices that quantifies heatwave severity relative to the local climate. In all regions, there were increases in morbidity (daily rates of ambulance call-outs and heat-related emergency presentations and hospital admissions) on heatwave days compared to non-heatwave days, which increased with heatwave severity. This study demonstrates that a consistent measure for heatwave severity, based on EHF, can be used to underpin public health warnings for climatically diverse areas.

Vulnerability to heatwaves and implications for public health interventions - A scoping review

BACKGROUND

Heatwaves form a serious public health threat, especially for vulnerable groups. Interventions such as active outreach programs, exposure reduction measures and monitoring and mapping of at-risk groups are increasingly implemented across the world but little is known about their effect.

OBJECTIVES

To assess how vulnerable groups are identified and reached in heat health interventions, to understand the effectiveness and efficiency of those interventions, and to identify research gaps in existing literature.

METHODS

We performed a literature search in relevant scientific literature databases and searched with a four element search model for articles published from 1995 onward. We extracted data on intervention measures, target group and evaluation of effectiveness and efficiency.

RESULTS

We identified 23 eligible studies. Patterns exist in type of interventions 1) to detect and 2) to influence extrinsic and intrinsic risk and protective factors. Results showed several intervention barriers related to the variety and intersection of these factors, as well as the self-perception of vulnerable groups, and misconceptions and unfavorable attitudes towards intervention benefits. While modest indications for the evidence on the effectiveness of interventions were found, efficiency remains unclear.

DISCUSSION

Interventions entailed logical combinations of measures, subsumed as packages. Evidence for effective and efficient intervention is limited by the difficulty to determine effects and because single measures are mutually dependent. Interventions prioritized promoting behavioral change and were based on behavioral assumptions that remain untested and mechanisms not worked out explicitly.

CONCLUSIONS

Multifaceted efforts are needed to tailor interventions, compiled in heat health warning systems and action plans for exposure reduction and protection of vulnerable populations, to fit the social, economic and geographical context. Besides adequately addressing relevant risk and protective factors, the challenge is to integrate perspectives of vulnerable groups. Future research should focus on intervention barriers and improving the methods of effectiveness and efficiency evaluation.

Heatwave and elderly mortality: An evaluation of death burden and health costs considering short-term mortality displacement

BACKGROUND

A heatwave can be a devastating natural disaster to human health, and elderly people are particularly vulnerable. With the continuing rise in earth's surface temperature alongside the world's aging population, research on the mortality burden of heatwave for the older population remains relatively sparse. The potential magnitude of benefits of averting such deaths may be considerable.

OBJECTIVES

This paper examined the short-term mortality displacement (or "harvesting") of heatwave, characterized the heatwave-mortality relationship, and estimated death burden and health costs attributable to heatwave among the elderly in Australia.

METHODS

We collected daily data on the temperature and deaths of people aged ≥75 years in the five largest cities of Australia (Sydney, Melbourne, Brisbane, Perth and Adelaide), totaling 368,767 deaths in different periods between 1988 and 2011. A total of 15-tiered heatwave definitions, based on intensity (95th to 99th percentiles of temperature distribution) and duration (two or more consecutive days), were used to quantify heatwave effects, using time-series regression and random-effects meta-analysis. We calculated attributable deaths for each city and by different types of heatwave. Potential economic benefits in monetary terms were also estimated, considering that heat-related deaths are avoidable.

RESULTS

Among the Australian elderly population, we found significant associations between heatwave and deaths, with raised mortality immediately in the first few days followed by lower-than-expected mortality. In general, heatwave was associated with an average death increase of 28% (95% confidence interval: 15% to 42%), and greater increases were mostly observed for more intense heatwaves across multiple megacities. During the study period, there were dozens to hundreds of deaths attributable to heatwave for each city, equating to an economic loss of several million Australian dollars every year. Although the estimated attributable deaths varied by heatwave intensity and duration, the pattern was not consistent across cities.

CONCLUSIONS

Heatwave caused harvesting effects on mortality in the elderly population of Australia, and contributed to a substantial amount of death burden and indirect financial costs. To lessen the health impacts of heatwave in the affected regions, effective heatwave early warning systems and interventions targeted at the elderly population could be beneficial, both now and in the future.

[Intervention effect assessment of response to heatwave in communities of four cities, China]

Objective: To evaluate the intervention effects of response to heatwave in communities of four cities, China. Methods: Baseline survey on heatwave and climate change related knowledge, attitude and practice (KAP) was conducted in the pilot communities in Harbin, Nanjing, Shenzhen and Chongqing, using face-to-face questionnaire interview in November, 2011 to November, 2013. Finally, 1 604 residents were interviewed. Intervention measures were implemented in summers of 2013 and 2014, including delivering early warning information of heatwave health risk and launching health education and promotion. The second survey was conducted in same communities using the same questionnaire and sampling method as baseline survey in November, 2014, and 1 640 residents were interviewed. The Chi-square test was used to compare the demographic characteristics and KAP of community residents between before and after intervention, and the factors that affected the intervention effect were selected by logistic multiple stepwise regression model. Results: The age of the residents interviewed before and after intervention was (46.4 ± 15.5) years and (45.0 ± 15.9) years, respectively. Overall, the residents' awareness rates of heatwave before and after intervention were 70.5% (1 131/1 604) and 82.9% (1 359/1 640) (χ²=69.40, P<0.001). The rate of residents who had wished to receive early warning information increased 6.3% (χ²=41.11, P<0.001), which reached 94.6% (1 551/1 604) after intervention from 88.3% (1 416/1 604) in baseline survey. Both heatwave health risk early warning and health education had big impacts to residents. There were 92.7% (1 105 residents) among the 1 192 residents who had received the early warning information arrange work and rest time according to the early warning information and 93.0% (1 231 residents) among the 1 323 residents who knew about health education activities being conducted in community thought that the community health education activities had made active role in protecting health from heatwaves. After a series of intervention, male had a effect on attitude about hot wave than female in Nanjing and Chongqing, OR (95%CI) were 1.48(1.02-2.16) and 1.45 (1.18-2.05) , respectively; compared with subjects below primary school education, people with college degree or above had higer KAP in all cities (ORs range from 1.18 to 2.05), P<0.05; regular physical exercise (ORs range from 1.39 to 2.70) also had profound impacts on KAP in all cities (P<0.05). Conclusion: s Early warning and health education were effective measures to enhance residents' response capacity to climate change.

Changes in relative fit of human heat stress indices to cardiovascular, respiratory, and renal hospitalizations across five Australian urban populations

Various human heat stress indices have been developed to relate atmospheric measures of extreme heat to human health impacts, but the usefulness of different indices across various health impacts and in different populations is poorly understood. This paper determines which heat stress indices best fit hospital admissions for sets of cardiovascular, respiratory, and renal diseases across five Australian cities. We hypothesized that the best indices would be largely dependent on location. We fit parent models to these counts in the summers (November-March) between 2001 and 2013 using negative binomial regression. We then added 15 heat stress indices to these models, ranking their goodness of fit using the Akaike information criterion. Admissions for each health outcome were nearly always higher in hot or humid conditions. Contrary to our hypothesis that location would determine the best-fitting heat stress index, we found that the best indices were related largely by health outcome of interest, rather than location as hypothesized. In particular, heatwave and temperature indices had the best fit to cardiovascular admissions, humidity indices had the best fit to respiratory admissions, and combined heat-humidity indices had the best fit to renal admissions. With a few exceptions, the results were similar across all five cities. The best-fitting heat stress indices appear to be useful across several Australian cities with differing climates, but they may have varying usefulness depending on the outcome of interest. These findings suggest that future research on heat and health impacts, and in particular hospital demand modeling, could better reflect reality if it avoided "all-cause" health outcomes and used heat stress indices appropriate to specific diseases and disease groups.

Heat and emergency room admissions in the Netherlands

Background

Due to a global warming-related increase in heatwaves, it is important to obtain detailed understanding of the relationship between heat and health. We assessed the relationship between heat and urgent emergency room admissions in the Netherlands.

Methods

We collected daily maximum temperature and relative humidity data over the period 2002–2007. Daily urgent emergency room admissions were divided by sex, age group and disease category. We used distributed lag non-linear Poisson models, estimating temperature-admission associations. We estimated the relative risk (RR) for urgent hospital admissions for a range of temperatures compared to a baseline temperature of 21 °C. In addition, we compared the impact of three different temperature scenarios on admissions using the RR.

Results

There is a positive relationship between increasing temperatures above 21 °C and the RR for urgent emergency room admissions for the disease categories ‘Potential heat-related diseases’ and ‘Respiratory diseases’. This relationship is strongest in the 85+ group. The RRs are strongest for lag 0. For admissions for ‘circulatory diseases’, there is only a small significant increase of RRs within the 85+ age group for moderate heat, but not for extreme heat. The RRs for a one-day event with extreme heat are comparable to the RRs for multiple-day events with moderate heat.

Conclusions

Hospitals should adjust the capacity of their emergency departments on warm days, and the days immediately thereafter. The elderly in particular should be targeted through prevention programmes to reduce harmful effects of heat. The fact that this increase in admissions already occurs in temperatures above 21 °C is different from previous findings in warmer countries. Given the similar impact of three consecutive days of moderate heat and one day of extreme heat on admissions, criteria for activation of national heatwave plans need adjustments based on different temperature scenarios.

Electronic supplementary material

The online version of this article (10.1186/s12889-017-5021-1) contains supplementary material, which is available to authorized users.

Decompose the association between heatwave and mortality: Which type of heatwave is more detrimental?

BACKGROUND

Heatwaves is the most hazardous natural disaster in Australia and its health impacts need to be well unveiled, but how to properly define a heatwave is still debatable. This study aimed to identify which type of heatwave is more detrimental to health and to elucidate which temperature indicator is more suitable for heatwave definition and early warning.

METHODS

We categorized temperature into extremely-hot and not-extremely-hot, and extremely-hot temperature refers to temperature at least ≥96th percentile of the monthly temperature distribution, and accordingly, heatwaves were categorized into four types: 1) Type I: extremely-hot days followed by extremely-hot nights (HW_both); 2) Type II: extremely-hot days followed by not-extremely-hot nights (HW_day); 3) Type III: not-extremely-hot days followed by extremely-hot nights (HW_night); and 4) Type IV: not-extremely-hot days followed by not-extremely-hot nights (HW_warm). A Poisson regression allowing for over-dispersion was used to examine the relationship between different types of heatwaves and mortality in Sydney, Melbourne and Brisbane using the data from 1988 to 2011.

RESULTS

Mortality in Brisbane increased significantly during HW_both and HW_warm, and mortality in Melbourne increased significantly during HW_both and HW_day. For Sydney, HW_both, HW_warm, and HW_day were all associated with mortality increase, although no appreciable difference in the magnitudes of mortality increase among these three heatwave types was observed. HW_night was not associated with any significant mortality increase in these cities. Mean temperature is the best temperature indicator for heatwaves in Brisbane and maximum temperature is the best temperature indicator for heatwaves in Melbourne.

CONCLUSIONS

Extremely-hot days rather than extremely-hot nights played a critical role in heatwave-related mortality. City-specific heatwave early warning may be optimal for Australia.

Impacts of extremely high temperature and heatwave on heatstroke in Chongqing, China

Few studies have reported the quantitative association between heat and heatstroke (HS) occurrence, particularly in China. The aim of this study was to quantitatively assess the association between high temperature/heatwave and HS occurrence in Chongqing. The daily HS data from 2009 to 2013 of Chongqing were extracted from Chongqing Center for Disease Control and Prevention. A Zero-inflated Poisson regression model (ZIP) with a logistic distribution was used to quantitatively analyze the impacts of the daily maximum temperature (Tmax) over the threshold on HS occurrence by gender, age, and severity of HS, after controlling for covariates including day of the week (DOW), relative humidity, and daily temperature range. Lag effects up to 10 days were analyzed. Heatwave intensity, which was classified into four levels according to the quartile of its values, was calculated by Tmax multiplied the duration of a heatwave. The excess risk of HS during heatwave with different intensity was analyzed. The Tmax threshold for HS was 34 °C in Chongqing. After adjusting for potential confounders, strong associations and age-specific lag effects between Tmax and daily HS occurrence were observed. The impacts of Tmax on total HS lasted for 7 days (lag0-6), with the highest excess risk (ER) value of 30.5% (95% CI 23.6 and 37.8%) on lag0 with each 1 °C increment in Tmax over the threshold. A slightly stronger temperature-HS association was detected in male compared to female. The population over 65 years had the highest ER and the younger adults aged 19-35 and 35-55 years also showed significant heat-HS associations. The number of daily cases increased with the increasing of duration of heatwave and the peak value occurred on the eleventh day of the heatwave. The excess risk of HS during the heatwave with 1 to 4 level of intensity increased by 2.54, 2.97, 5.61, and 11.3 times, respectively, as compared with that of non-heatwave. Extreme heat is becoming a huge threat to public health due to the strong temperature-HS associations in Chongqing. Climate change with increasing temperatures may make the situation worse. Our results can provide reference for developing and improving relevant public health strategies and early extreme weather and health warning system to prevent and reduce the health risks due to extreme weather and climate change in Chongqing.

Heatwave and risk of hospitalization: A multi-province study in Vietnam

The effects of heatwaves on morbidity in developing and tropical countries have not been well explored. The purpose of this study was to examine the relationship between heatwaves and hospitalization and the potential influence of socio-economic factors on this relationship in Vietnam. Generalized Linear Models (GLM) with Poisson family and Distributed Lag Models (DLM) were applied to evaluate the effect of heatwaves for each province (province-level effect). A random-effects meta-analysis was applied to calculate the pooled estimates (country-level effects) for 'all causes', infectious, cardiovascular, and respiratory admissions queried by lag days, regions, sex, and ages. We used random-effects meta-regression to explore the potential influence of socio-economic factors on the relationship between heatwaves and hospitalization. The size of province-level effects varied across provinces. The pooled estimates show that heatwaves were significantly associated with a 2.5% (95%CI: 0.8-4.3) and 3.8% (95%CI, 1.5-6.2) increase in all causes and infectious admissions at lag 0. Cardiovascular and respiratory admissions (0.8%, 95%CI: -1.6-3.3; 2.2%, 95%CI: -0.7-5.2) were not significantly increased after a heatwave event. The risk of hospitalization due to heatwaves was higher in the North than in the South for all causes (5.4%, 95%CI: -0.1-11.5 versus 1.3%, 95%CI: 0.1-2.6), infectious (11.2%, 95%CI: 3.1-19.9 versus 3.2%, 95%CI: 0.7-5.7), cardiovascular (7.5%, 95%CI: 1.1-14.4 versus -1.2%, 95%CI: -2.6-2.3), and respiratory diseases (2.7%, 95%CI: -5.4-11.5 versus 2.1%, 95%CI: -0.8-1.2). A non-significant influence of socio-economic factors on the relationship between heatwave and hospitalization was observed. This study provides important evidence and suggests implications for the projected impacts of climate change related extreme weather. Climate change adaptation programs of the health sector should be developed to protect residents from the effects of extreme weather events such as heatwaves in Vietnam.