Temperature variation and heat wave and cold spell impacts on years of life lost among the urban poor population of Nairobi, Kenya

Weather extremes are associated with adverse health outcomes, including mortality. Studies have investigated the mortality risk of temperature in terms of excess mortality, however, this risk estimate may not be appealing to policy makers assessing the benefits expected for any interventions to be adopted. To provide further evidence of the burden of extreme temperatures, we analyzed the effect of temperature on years of life lost (YLL) due to all-cause mortality among the population in two urban informal settlements. YLL was generated based on the life expectancy of the population during the study period by applying a survival analysis approach. Association between daily maximum temperature and YLL was assessed using a distributed lag nonlinear model. In addition, cold spell and heat wave effects, as defined according to different percentiles, were investigated. The exposure-response curve between temperature and YLL was J-shaped, with the minimum mortality temperature (MMT) of 26 °C. An average temperature of 21 °C compared to the MMT was associated with an increase of 27.4 YLL per day (95% CI, 2.7-52.0 years). However, there was no additional effect for extended periods of cold spells, nor did we find significant associations between YLL to heat or heat waves. Overall, increased YLL from all-causes were associated with cold spells indicating the need for initiating measure for reducing health burdens.

Children's health and vulnerability in outdoor microclimates: A comprehensive review

BACKGROUND

Children are routinely identified as a vulnerable population in environmental health risk assessments, experiencing adverse health outcomes due to exposure to a suite of atmospheric constituents.

OBJECTIVE

To provide a substantive overview of the research literature pertaining to biometeorological effects on children. Key information areas within urban environmental health research related to atmospheric variables (heat, air pollution, radiation) are assessed and integrated to better understand health outcomes and vulnerabilities in children. Critical avenues for improvement and understanding of children's health related to such biophysical parameters are also identified.

METHODS

This comprehensive review assesses past and current primary studies, organizational reports, educational books, and review articles. Emphasis is placed on the differential ambient exposures to temperature, air pollution, and radiation within urban microclimates commonly used by children (e.g., schoolyards, urban parks), and the resulting health impacts.

DISCUSSION

Exposure to heat, air pollution, and radiation are often enhanced in urban areas, specifically under the current design of the majority of outdoor child play places. Many heat indices, energy budget models, and health outcome studies fail to adequately parameterize children, yet those that do find enhanced vulnerability to ambient stressors, particularly heat and air pollution. Such environmental exposures relate strongly to behavior, activity, asthma, obesity, and overall child well-being. Current research indicates that a changing climate, growing urban population, and unsustainable design are projected to pose increasing complications.

CONCLUSIONS

Evidence-based research to link children's health, physiology, and behavior to atmospheric extremes is an important future research avenue, underscoring the fact that children are among the population groups disproportionately affected by ambient extremes. However, current methods and population-based models lack child-specific inputs and outputs, as well as designated thresholds for accurate predictions of child health impacts. More substantive evidence is needed for applicable child-specific policies and guidelines.

Heat and mortality in New York City since the beginning of the 20th century

BACKGROUND

Heat is recognized as one of the deadliest weather-related phenomena. Although the impact of high temperatures on mortality has been a subject of extensive research, few previous studies have assessed the impact of population adaptation to heat.

METHODS

We examined adaptation patterns by analyzing daily temperature and mortality data spanning more than a century in New York City. Using a distributed-lag nonlinear model, we analyzed the heat-mortality relation in adults age 15 years or older in New York City during 2 periods: 1900-1948 and 1973-2006, to quantify population adaptation to high temperatures over time.

RESULTS

During the first half of the century, the decade-specific relative risk of mortality at 29°C vs. 22°C ranged from 1.30 (95% confidence interval [CI]= 1.25-1.36) in the 1910s to 1.43 (1.37-1.49) in the 1900s. Since the 1970s, however, there was a gradual and substantial decline in the relative risk, from 1.26 (1.22-1.29) in the 1970s to 1.09 (1.05-1.12) in the 2000s. Age-specific analyses indicated a greater risk for people age 65 years and older in the first part of the century, but there was less evidence for enhanced risk among this older age group in more recent decades.

CONCLUSION

The excess mortality with high temperatures observed between 1900 and 1948 was substantially reduced between 1973 and 2006, indicating population adaption to heat in recent decades. These findings may have implications for projecting future impacts of climate change on mortality.

Approaching environmental health disparities and green spaces: an ecosystem services perspective

Health disparities occur when adverse health conditions are unequal across populations due in part to gaps in wealth. These disparities continue to plague global health. Decades of research suggests that the natural environment can play a key role in sustaining the health of the public. However, the influence of the natural environment on health disparities is not well-articulated. Green spaces provide ecosystem services that are vital to public health. This paper discusses the link between green spaces and some of the nation’s leading health issues such as obesity, cardiovascular health, heat-related illness, and psychological health. These associations are discussed in terms of key demographic variables—race, ethnicity, and income. The authors also identify research gaps and recommendations for future research.

Evaluating the performance of a climate-driven mortality model during heat waves and cold spells in Europe

The impact of climate change on human health is a serious concern. In particular, changes in the frequency and intensity of heat waves and cold spells are of high relevance in terms of mortality and morbidity. This demonstrates the urgent need for reliable early-warning systems to help authorities prepare and respond to emergency situations. In this study, we evaluate the performance of a climate-driven mortality model to provide probabilistic predictions of exceeding emergency mortality thresholds for heat wave and cold spell scenarios. Daily mortality data corresponding to 187 NUTS2 regions across 16 countries in Europe were obtained from 1998–2003. Data were aggregated to 54 larger regions in Europe, defined according to similarities in population structure and climate. Location-specific average mortality rates, at given temperature intervals over the time period, were modelled to account for the increased mortality observed during both high and low temperature extremes and differing comfort temperatures between regions. Model parameters were estimated in a Bayesian framework, in order to generate probabilistic simulations of mortality across Europe for time periods of interest. For the heat wave scenario (1–15 August 2003), the model was successfully able to anticipate the occurrence or non-occurrence of mortality rates exceeding the emergency threshold (75th percentile of the mortality distribution) for 89% of the 54 regions, given a probability decision threshold of 70%. For the cold spell scenario (1–15 January 2003), mortality events in 69% of the regions were correctly anticipated with a probability decision threshold of 70%. By using a more conservative decision threshold of 30%, this proportion increased to 87%. Overall, the model performed better for the heat wave scenario. By replacing observed temperature data in the model with forecast temperature, from state-of-the-art European forecasting systems, probabilistic mortality predictions could potentially be made several months ahead of imminent heat waves and cold spells.

Increased hospital admissions associated with extreme-heat exposure in King County, Washington, 1990-2010

Increased morbidity and mortality have been associated with extreme heat events, particularly in temperate climates. Few epidemiologic studies have considered the impact of extreme heat events on hospitalization rates in the Pacific Northwest region. This study quantifies the historic (May to September 1990-2010) heat-morbidity relationship in the most populous Pacific Northwest County, King County, Washington. A relative risk (RR) analysis was used to explore the association between heat and all non-traumatic hospitalizations on 99th percentile heat days, whereas a time series analysis using a piecewise linear model approximation was used to estimate the effect of heat intensity on hospitalizations, adjusted for temporal trends and day of the week. A non-statistically significant 2% [95% CI: 1.02 (0.98, 1.05)] increase in hospitalization risk, on a heat day vs. a non-heat day, was noted for all-ages and all non-traumatic causes. When considering the effect of heat intensity on admissions, we found a statistically significant 1.59% (95% CI: 0.9%, 2.29%) increase in admissions per degree increase in humidex above 37.4°C. Admissions stratified by cause and age produced statistically significant results with both relative risk and time series analyses for nephritis and nephrotic syndromes, acute renal failure, and natural heat exposure hospitalizations. This study demonstrates that heat, expressed as humidex, is associated with increased hospital admissions. When stratified by age and cause of admission, the non-elderly age groups (<85 years) experience significant risk for nephritis and nephrotic syndromes, acute renal failure, natural heat exposure, chronic obstructive pulmonary disease, and asthma hospitalizations.

Changes in antioxidants are critical in determining cell responses to short- and long-term heat stress

Heat stress can have deleterious effects on plant growth by impairing several physiological processes. Plants have several defense mechanisms that enable them to cope with high temperatures. The synthesis and accumulation of heat shock proteins (HSPs), as well as the maintenance of an opportune redox balance play key roles in conferring thermotolerance to plants. In this study changes in redox parameters, the activity and/or expression of reactive oxygen species (ROS) scavenging enzymes and the expression of two HSPs were studied in tobacco Bright Yellow-2 (TBY-2) cells subjected to moderate short-term heat stress (SHS) and long-term heat stress (LHS). The results indicate that TBY-2 cells subjected to SHS suddenly and transiently enhance antioxidant systems, thus maintaining redox homeostasis and avoiding oxidative damage. The simultaneous increase in HSPs overcomes the SHS and maintains the metabolic functionality of cells. In contrast the exposure of cells to LHS significantly reduces cell growth and increases cell death. In the first phase of LHS, cells enhance antioxidant systems to prevent the formation of an oxidizing environment. Under prolonged heat stress, the antioxidant systems, and particularly the enzymatic ones, are inactivated. As a consequence, an increase in H2 O2 , lipid peroxidation and protein oxidation occurs. This establishment of oxidative stress could be responsible for the increased cell death. The rescue of cell growth and cell viability, observed when TBY-2 cells were pretreated with galactone-γ-lactone, the last precursor of ascorbate, and glutathione before exposure to LHS, highlights the crucial role of antioxidants in the acquisition of basal thermotolerance.

The Effect of Fabric Type of Common Iranian Working Clothes on the Induced Cardiac and Physiological Strain Under Heat Stress

The present study compared the effect of fabric type of working clothes on heat strain responses in different levels of physical workload and under different kinds of weather conditions. Four kinds of working clothing fabric that are greatly popular in Iranian industry were assessed on 18 healthy male at 2 environments: hot and humid (dry temperature [DBt]: 35°C and relative humidity [RH]: 70%) and hot and dry (DBt: 40°C and RH: 40%). The physiological responses such as heart rate and core body temperature were reported. It was found that there were no significant differences between different types of clothing fabric on cardiac and physiological parameters. It can be recommended that 100% cotton clothing ensemble during low-workload activities and 30.2% cotton-69.8% polyester clothing ensemble during moderate-workload activities is used for Iranian workers to maintain the cardiac and physiological strains as low as possible.

Variability in temperature-related mortality projections under climate change

BACKGROUND

Most studies that have assessed impacts on mortality of future temperature increases have relied on a small number of simulations and have not addressed the variability and sources of uncertainty in their mortality projections.

OBJECTIVES

We assessed the variability of temperature projections and dependent future mortality distributions, using a large panel of temperature simulations based on different climate models and emission scenarios.

METHODS

We used historical data from 1990 through 2007 for Montreal, Quebec, Canada, and Poisson regression models to estimate relative risks (RR) for daily nonaccidental mortality in association with three different daily temperature metrics (mean, minimum, and maximum temperature) during June through August. To estimate future numbers of deaths attributable to ambient temperatures and the uncertainty of the estimates, we used 32 different simulations of daily temperatures for June-August 2020-2037 derived from three global climate models (GCMs) and a Canadian regional climate model with three sets of RRs (one based on the observed historical data, and two on bootstrap samples that generated the 95% CI of the attributable number (AN) of deaths). We then used analysis of covariance to evaluate the influence of the simulation, the projected year, and the sets of RRs used to derive the attributable numbers of deaths.

RESULTS

We found that < 1% of the variability in the distributions of simulated temperature for June-August of 2020-2037 was explained by differences among the simulations. Estimated ANs for 2020-2037 ranged from 34 to 174 per summer (i.e., June-August). Most of the variability in mortality projections (38%) was related to the temperature-mortality RR used to estimate the ANs.

CONCLUSIONS

The choice of the RR estimate for the association between temperature and mortality may be important to reduce uncertainty in mortality projections.

The 2011 heat wave in Greater Houston: Effects of land use on temperature

Effects of land use on temperatures during severe heat waves have been rarely studied. This paper examines land use-temperature associations during the 2011 heat wave in Greater Houston. We obtained high resolution of satellite-derived land use data from the US National Land Cover Database, and temperature observations at 138 weather stations from Weather Underground, Inc (WU) during the August of 2011, which was the hottest month in Houston since 1889. Land use regression and quantile regression methods were applied to the monthly averages of daily maximum/mean/minimum temperatures and 114 land use-related predictors. Although selected variables vary with temperature metric, distance to the coastline consistently appears among all models. Other variables are generally related to high developed intensity, open water or wetlands. In addition, our quantile regression analysis shows that distance to the coastline and high developed intensity areas have larger impacts on daily average temperatures at higher quantiles, and open water area has greater impacts on daily minimum temperatures at lower quantiles. By utilizing both land use regression and quantile regression on a recent heat wave in one of the largest US metropolitan areas, this paper provides a new perspective on the impacts of land use on temperatures. Our models can provide estimates of heat exposures for epidemiological studies, and our findings can be combined with demographic variables, air conditioning and relevant diseases information to identify 'hot spots' of population vulnerability for public health interventions to reduce heat-related health effects during heat waves.

Summertime acute heat illness in U.S. emergency departments from 2006 through 2010: analysis of a nationally representative sample

BACKGROUND

Patients with acute heat illness present primarily to emergency departments (EDs), yet little is known regarding these visits.

OBJECTIVE

We aimed to describe acute heat illness visits to U.S. EDs from 2006 through 2010 and identify factors associated with hospital admission or with death in the ED.

METHODS

We extracted ED case-level data from the Nationwide Emergency Department Sample (NEDS) for 2006-2010, defining cases as ED visits from May through September with any heat illness diagnosis (ICD-9-CM 992.0-992.9). We correlated visit rates and temperature anomalies, analyzed demographics and ED disposition, identified risk factors for adverse outcomes, and examined ED case fatality rates (CFR).

RESULTS

There were 326,497 (95% CI: 308,372, 344,658) cases, with 287,875 (88.2%) treated and released, 38,392 (11.8%) admitted, and 230 (0.07%) died in the ED. Heat illness diagnoses were first-listed in 68%. 74.7% had heat exhaustion, 5.4% heat stroke. Visit rates were highly correlated with annual temperature anomalies (Pearson correlation coefficient 0.882, p = 0.005). Treat-and-release rates were highest for younger adults (26.2/100,000/year), whereas hospitalization and death-in-the-ED rates were highest for older adults (6.7 and 0.03/100,000/year, respectively); all rates were highest in rural areas. Heat stroke had an ED CFR of 99.4/10,000 (95% CI: 78.7, 120.1) visits and was diagnosed in 77.0% of deaths. Adjusted odds of hospital admission or death in the ED were higher among elders, males, urban and low-income residents, and those with chronic conditions.

CONCLUSIONS

Heat illness presented to the ED frequently, with highest rates in rural areas. Case definitions should include all diagnoses. Visit rates were correlated with temperature anomalies. Heat stroke had a high ED CFR. Males, elders, and the chronically ill were at greatest risk of admission or death in the ED. Chronic disease burden exponentially increased this risk.

Managing health impacts of heat in South East Queensland, Australia

Heatwaves kill more people than any other natural hazard in Australia. Current literature on managing health risks of heatwaves highlights the importance of implementing urban planning measures, and engaging with vulnerable groups on a local level to better understand perceptions of risk and tailor health protection measures. This paper reviews arrangements to reduce heatwave health risks in South East Queensland in response to these themes. A literature search and document analysis, stakeholder interviews, and multi-stakeholder cross-sectoral workshops revealed that although heatwave management is not always considered by local government and disaster management stakeholders, many urban planning measures to minimize urban heat have been pursued. However, greater information from vulnerable groups is still needed to better inform heatwave management measures.

Acclimatization across space and time in the effects of temperature on mortality: a time-series analysis

BACKGROUND

Climate change has increased the days of unseasonal temperature. Although many studies have examined the association between temperature and mortality, few have examined the timing of exposure where whether this association varies depending on the exposure month even at the same temperature. Therefore, we investigated monthly differences in the effects of temperature on mortality in a study comprising a wide range of weather and years, and we also investigated heterogeneity among regions.

METHODS

We analyzed 38,005,616 deaths from 148 cities in the U.S. from 1973 through 2006. We fit city specific Poisson regressions to examine the effect of temperature on mortality separately for each month of the year, using penalized splines. We used cluster analysis to group cities with similar weather patterns, and combined results across cities within clusters using meta-smoothing.

RESULTS

There was substantial variation in the effects of the same temperature by month. Heat effects were larger in the spring and early summer and cold effects were larger in late fall. In addition, heat effects were larger in clusters where high temperatures were less common, and vice versa for cold effects.

CONCLUSIONS

The effects of a given temperature on mortality vary spatially and temporally based on how unusual it is for that time and location. This suggests changes in variability of temperature may be more important for health as climate changes than changes of mean temperature. More emphasis should be placed on warnings targeted to early heat/cold temperature for the season or month rather than focusing only on the extremes.

Perceived adverse health effects of heat and their determinants in deprived neighbourhoods: a cross-sectional survey of nine cities in Canada

This study identifies several characteristics of individuals who report their physical and/or mental health as being adversely affected by summertime heat and humidity, within the most disadvantaged neighbourhoods of the nine largest cities of Québec (Canada). The study is cross-sectional by stratified representative sample; 3485 people were interviewed in their residence. The prevalence of reported impacts was 46%, mostly physical health. Female gender and long-term medical leave are two impact risk indicators in people <65 years of age. Low income and air conditioning at home are risk indicators at all ages. Results for having ≥2 diagnoses of chronic diseases, particularly for people self-describing as in poor health (odds ratio, OR_<65 = 5.6; OR_≥65 = 4.2), and perceiving daily stress, are independent of age. The prevalence of reported heat-related health impacts is thus very high in those inner cities, with notable differences according to age, stress levels and long-term medical leave, previously unmentioned in the literature. Finally, the total number of pre-existing medical conditions seems to be a preponderant risk factor. This study complements the epidemiologic studies based on mortality or severe morbidity and shows that the heat-related burden of disease appears very important in those communities, affecting several subgroups differentially.

The spatial distribution of health vulnerability to heat waves in Guangdong Province, China

Background

International literature has illustrated that the health impacts of heat waves vary according to differences in the spatial variability of high temperatures and the social and economic characteristics of populations and communities. However, to date there have been few studies that quantitatively assess the health vulnerability to heat waves in China.

Objectives

To assess the spatial distribution of health vulnerability to heat waves in Guangdong Province, China.

Methods

A vulnerability framework including dimensions of exposure, sensitivity, and adaptive capacity was employed. The last two dimensions were called social vulnerability. An indicator pool was proposed with reference to relevant literatures, local context provided by relevant local stakeholder experts, and data availability. An analytic hierarchy process (AHP) and a principal component analysis were used to determine the weight of indicators. A multiplicative vulnerability index (VI) was constructed for each district/county of Guangdong province, China.

Results

A total of 13 items (two for exposure, six for sensitivity, and five for adaptive capacity) were proposed to assess vulnerability. The results of an AHP revealed that the average VI in Guangdong Province was 0.26 with the highest in the Lianzhou and Liannan counties of Qingyuan (VI=0.50) and the lowest in the Yantian district of Shenzhen (VI=0.08). Vulnerability was gradiently distributed with higher levels in northern inland regions and lower levels in southern coastal regions. In the principal component analysis, three components were isolated from the 11 social vulnerability indicators. The estimated vulnerability had a similar distribution pattern with that estimated by AHP (Intraclass correlation coefficient (ICC)=0.98, p<0.01).

Conclusions

Health vulnerability to heat waves in Guangdong Province had a distinct spatial distribution, with higher levels in northern inland regions than that in the southern coastal regions.

Association of climate variability and childhood diarrhoeal disease in rural Bangladesh, 2000-2006

This study examined the effects of meteorological factors, particularly, extreme weather events, on the prevalence of childhood diarrhoeal disease in Matlab, Bangladesh. Logistic regression models were used to examine impacts of temperature, rainfall and the extreme weather factors (the number of hot days and days with heavy rainfall) on childhood diarrhoea from 2000 to 2006 at the bari (cluster of dwellings) level. The results showed that the increases in the number of hot days and days with heavy rainfall were associated with an increase in daily diarrhoea cases by 0·8-3·8% and 1-6·2%, respectively. The results from multivariable stepwise models showed that the extreme weather factors were still positively associated with childhood diarrhoea, while the associations for average temperature and rainfall could be negative after other variables were controlled. The findings showed that not only the intensity, but also the frequency of extreme weather events had significant effects on childhood diarrhoea.

Using forecast and observed weather data to assess performance of forecast products in identifying heat waves and estimating heat wave effects on mortality

BACKGROUND

Heat wave and health warning systems are activated based on forecasts of health-threatening hot weather.

OBJECTIVE

We estimated heat-mortality associations based on forecast and observed weather data in Detroit, Michigan, and compared the accuracy of forecast products for predicting heat waves.

METHODS

We derived and compared apparent temperature (AT) and heat wave days (with heat waves defined as ≥ 2 days of daily mean AT ≥ 95th percentile of warm-season average) from weather observations and six different forecast products. We used Poisson regression with and without adjustment for ozone and/or PM10 (particulate matter with aerodynamic diameter ≤ 10 μm) to estimate and compare associations of daily all-cause mortality with observed and predicted AT and heat wave days.

RESULTS

The 1-day-ahead forecast of a local operational product, Revised Digital Forecast, had about half the number of false positives compared with all other forecasts. On average, controlling for heat waves, days with observed AT = 25.3°C were associated with 3.5% higher mortality (95% CI: -1.6, 8.8%) than days with AT = 8.5°C. Observed heat wave days were associated with 6.2% higher mortality (95% CI: -0.4, 13.2%) than non-heat wave days. The accuracy of predictions varied, but associations between mortality and forecast heat generally tended to overestimate heat effects, whereas associations with forecast heat waves tended to underestimate heat wave effects, relative to associations based on observed weather metrics.

CONCLUSIONS

Our findings suggest that incorporating knowledge of local conditions may improve the accuracy of predictions used to activate heat wave and health warning systems.

Challenges associated with projecting urbanization-induced heat-related mortality

Maricopa County, Arizona, anchor to the fastest growing megapolitan area in the United States, is located in a hot desert climate where extreme temperatures are associated with elevated risk of mortality. Continued urbanization in the region will impact atmospheric temperatures and, as a result, potentially affect human health. We aimed to quantify the number of excess deaths attributable to heat in Maricopa County based on three future urbanization and adaptation scenarios and multiple exposure variables. Two scenarios (low and high growth projections) represent the maximum possible uncertainty range associated with urbanization in central Arizona, and a third represents the adaptation of high-albedo cool roof technology. Using a Poisson regression model, we related temperature to mortality using data spanning 1983-2007. Regional climate model simulations based on 2050-projected urbanization scenarios for Maricopa County generated distributions of temperature change, and from these predicted changes future excess heat-related mortality was estimated. Subject to urbanization scenario and exposure variable utilized, projections of heat-related mortality ranged from a decrease of 46 deaths per year (-95%) to an increase of 339 deaths per year (+359%). Projections based on minimum temperature showed the greatest increase for all expansion and adaptation scenarios and were substantially higher than those for daily mean temperature. Projections based on maximum temperature were largely associated with declining mortality. Low-growth and adaptation scenarios led to the smallest increase in predicted heat-related mortality based on mean temperature projections. Use of only one exposure variable to project future heat-related deaths may therefore be misrepresentative in terms of direction of change and magnitude of effects. Because urbanization-induced impacts can vary across the diurnal cycle, projections of heat-related health outcomes that do not consider place-based, time-varying urban heat island effects are neglecting essential elements for policy relevant decision-making.

Heat- and cold-stress effects on cardiovascular mortality and morbidity among urban and rural populations in the Czech Republic

Several studies have examined the relationship of high and low air temperatures to cardiovascular mortality in the Czech Republic. Much less is understood about heat-/cold-related cardiovascular morbidity and possible regional differences. This paper compares the effects of warm and cold days on excess mortality and morbidity for cardiovascular diseases (CVDs) in the city of Prague and a rural region of southern Bohemia during 1994-2009. Population size and age structure are similar in the two regions. The results are evaluated for selected population groups (men and women). Excess mortality (number of deaths) and morbidity (number of hospital admissions) were determined as differences between observed and expected daily values, the latter being adjusted for long-term changes, annual and weekly cycles, and epidemics of influenza/acute respiratory infections. Generally higher relative excess CVD mortality on warm days than on cold days was identified in both regions. In contrast to mortality, weak excess CVD morbidity was observed for both warm and cold days. Different responses of individual CVDs to heat versus cold stress may be caused by the different nature of each CVD and different physiological processes induced by heat or cold stress. The slight differences between Prague and southern Bohemia in response to heat versus cold stress suggest the possible influence of environmental and socioeconomic factors such as the effects of urban heat island and exposure to air pollution, lifestyle differences, and divergence in population structure, which may result in differing vulnerability of urban versus rural population to temperature extremes.

Impact of heat waves on mortality in Croatia

The aim of this work was to determine the criteria for heat loads associated with an increase in mortality in different climatic regions of Croatia. The relationship between heat stress and mortality was analysed for the period 1983-2008. The input series is excess mortality defined as the deviations of mortality from expected values determined by means of a Gaussian filter of 183 days. The assessment of the thermal environment was performed by means of physiologically equivalent temperature (PET). The curve depicting the relationship between mortality and temperature has a U shape, with increased mortality in both the cold and warm parts of the scale but more pronounced in the warm part. The threshold temperature for increased mortality was determined using a scatter plot and fitting data by means of moving average of mortality; the latter is defined as the temperature at which excess mortality becomes significant. The values are higher in the continental part of Croatia than at the coast due to the refreshing influence of the sea during the day. The same analysis on a monthly basis shows that at the beginning of the warm season increased mortality occurs at a lower temperature compared with later on in the summer, and the difference is up to 15 °C between August and April. The increase in mortality is highest during the first 3-5 days and after that it decreases and falls below the expected value. Long-lasting heat waves present an increased risk, but in very long heat waves the increase in mortality is reduced due to mortality displacement.

The effect of pre-existing medical conditions on heat stroke during hot weather in South Korea

BACKGROUND

Heat stroke contributes considerably to morbidity and mortality in hot weather, but it is unclear whether pre-existing medical conditions increase the risk of heat stroke. The purpose of this study was to assess the association between heat stroke and pre-existing medical conditions in South Korea.

METHODS

A case-control study was conducted using data from a nationwide surveillance system for heat illnesses in 2012. Individuals with heat stroke were identified and compared to control subjects with mild heat illness such as heat exhaustion, heat edema, heat cramps, and heat syncope. Categories of pre-existing medical conditions included cardio/cerebrovascular disease, respiratory disease, neuropsychiatric disorder, and diabetes mellitus. Associations between heat stroke and pre-existing medical conditions were assessed by multivariate logistic regression analyses.

RESULTS

Of 968 eligible patients, 178 (18.4%) presented with heat stroke. Patients with pre-existing medical conditions were relatively greater in the heat stroke group than in the control group (40.4% and 23.9%, respectively). Neuropsychiatric disorder was associated with an increased odds of heat stroke after adjustment for covariates (adjusted odds ratio, 7.69; 95% CI, 4.06-14.54). There were no significant relationships between heat stroke and other medical conditions (cardio/cerebrovascular disease: 0.66, 0.40-1.06; respiratory disease: 1.44, 0.35-5.89; diabetes mellitus: 1.16, 0.58-2.34).

CONCLUSIONS

Pre-existing neuropsychiatric disorder was associated with an increased risk of heat stroke. National strategies and clinical guidance for such patients should be initiated to prevent fatal events.

The use of Bayesian inference to inform the surveillance of temperature-related occupational morbidity in Ontario, Canada, 2004-2010

PURPOSE

To assess the associations of occupational heat and cold-related illnesses presenting in emergency departments in south western Ontario, Canada, with daily meteorological conditions using Bayesian inference.

METHODOLOGY

Meteorological and air pollution data for the south western economic region of Ontario were gathered from Environment Canada and the Ministry of Environment. Daily heat and cold-related emergency department visits clinically attributed to work from 2004 to 2010 were tabulated. A novel application of Bayesian inference on a flexible Poisson time series model was undertaken to examine linear and non-linear associations between average, regional meteorological conditions and daily morbidity rates, to adjust for relevant confounders and temporal trends, and to consider potential interactions.

RESULTS

Bilinear associations were observed between regional temperatures and morbidities resulting from extreme temperature exposures. The median increase in the daily rate of emergency department visits for heat illness was 75% for each degree above 22°C (posterior 95% credible interval (CI) relative rate=1.56-1.99) in the daily maximum temperature. Below 0°C, rates of occupational cold illness increased by a median of 15% for each degree decrease in the minimum temperature (posterior 95% CI 0.80-0.91); wind speed also had a significant effect.

CONCLUSIONS

The observed associations can inform occupational surveillance and injury prevention programming, as well as public health efforts targeting vulnerable populations. Methodologically, the use of Bayesian inference in time series analyses of meteorological exposures is feasible and conducive to providing accurate advice for policy and practice.

Characterizing the effect of summer temperature on heatstroke-related emergency ambulance dispatches in the Kanto area of Japan

Despite rising concern on the impact of heat on human health, the risk of high summer temperature on heatstroke-related emergency dispatches is not well understood in Japan. A time-series study was conducted to examine the association between apparent temperature and daily heatstroke-related ambulance dispatches (HSAD) within the Kanto area of Japan. A total of 12,907 HSAD occurring from 2000 to 2009 in five major cities-Saitama, Chiba, Tokyo, Kawasaki, and Yokohama-were analyzed. Generalized additive models and zero-inflated Poisson regressions were used to estimate the effects of daily maximum three-hour apparent temperature (AT) on dispatch frequency from May to September, with adjustment for seasonality, long-term trend, weekends, and public holidays. Linear and non-linear exposure effects were considered. Effects on days when AT first exceeded its summer median were also investigated. City-specific estimates were combined using random effects meta-analyses. Exposure-response relationship was found to be fairly linear. Significant risk increase began from 21 °C with a combined relative risk (RR) of 1.22 (95% confidence interval, 1.03-1.44), increasing to 1.49 (1.42-1.57) at peak AT. When linear exposure was assumed, combined RR was 1.43 (1.37-1.50) per degree Celsius increment. Overall association was significant the first few times when median AT was initially exceeded in a particular warm season. More than two-thirds of these initial hot days were in June, implying the harmful effect of initial warming as the season changed. Risk increase that began early at the fairly mild perceived temperature implies the need for early precaution.

When it rains, it pours: future climate extremes and health

BACKGROUND

The accelerating accumulation of greenhouse gases in the Earth's atmosphere is changing global environmental conditions in unprecedented and potentially irreversible ways. Climate change poses a host of challenges to the health of populations through complex direct and indirect mechanisms. The direct effects include an increased frequency of heat waves, rising sea levels that threaten low-lying communities, anticipated extremes in the global hydrologic cycle (droughts, floods, and intense storms), and adverse effects on agricultural production and fisheries due to environmental stressors and changes in land use. Indirectly, climate change is anticipated to threaten health by worsening urban air pollution and increasing rates of infectious (particularly waterborne and vector-borne) disease transmission.

OBJECTIVE

To provide a state-of-the-science review on the health consequences of a changing climate.

FINDINGS

Environmental public health researchers have concluded that, on balance, adverse health outcomes will dominate under these changed climatic conditions. The number of pathways through which climate change can affect the health of populations makes this environmental health threat one of the largest and most formidable of the new century. Geographic location plays an influential role the potential for adverse health effects caused by climate change, and certain regions and populations are more vulnerable than others to expected health effects. Two kinds of strategies are available for responding to climate change: mitigation policies (which aim to reduce greenhouse gas emissions) and adaptation measures (relating to preparedness for anticipated impacts).

CONCLUSIONS

To better understand and address the complex nature of health risks posed by climate change, interdisciplinary collaboration is critical. Efforts to move beyond our current reliance on fossil fuels to cleaner, more sustainable energy sources may offer some of the greatest health opportunities in more than a century and cobenefits beyond the health sector. Because the nations least responsible for climate change are most vulnerable to its effects, the challenge to reduce greenhouse gas emissions is not merely technical, but also moral.

Racial and socioeconomic disparities in heat-related health effects and their mechanisms: a review

Adaptation to increasing extreme heat in a changing climate requires a precise understanding of who is most vulnerable to the health effects of extreme heat. The evidence for race, ethnicity, income, education and occupation, at the individual and area levels, as indicators of vulnerability is reviewed. The evidence for the social, behavioral and technological mechanisms by which racial and socioeconomic disparities in vulnerability exist is also reviewed. These characteristics include cardiorespiratory, renal and endocrine comorbidities; cognitive, mental or physical disabilities; medication use; housing characteristics; neighborhood characteristics such as urban heat islands, crime and safety; social isolation; and individual behaviors such as air conditioning use, opening windows and using fans and use of cooler public spaces. Pre-existing and future research identifying these more proximal indicators of vulnerability will provide information that is more generalizable across locations and time to aid in identifying who to target for prevention of heat-associated morbidity and mortality.

What weather variables are important in predicting heat-related mortality? A new application of statistical learning methods

Hot weather increases risk of mortality. Previous studies used different sets of weather variables to characterize heat stress, resulting in variation in heat-mortality associations depending on the metric used. We employed a statistical learning method - random forests - to examine which of the various weather variables had the greatest impact on heat-related mortality. We compiled a summertime daily weather and mortality counts dataset from four U.S. cities (Chicago, IL; Detroit, MI; Philadelphia, PA; and Phoenix, AZ) from 1998 to 2006. A variety of weather variables were ranked in predicting deviation from typical daily all-cause and cause-specific death counts. Ranks of weather variables varied with city and health outcome. Apparent temperature appeared to be the most important predictor of heat-related mortality for all-cause mortality. Absolute humidity was, on average, most frequently selected as one of the top variables for all-cause mortality and seven cause-specific mortality categories. Our analysis affirms that apparent temperature is a reasonable variable for activating heat alerts and warnings, which are commonly based on predictions of total mortality in next few days. Additionally, absolute humidity should be included in future heat-health studies. Finally, random forests can be used to guide the choice of weather variables in heat epidemiology studies.

Is enough attention given to climate change in health service planning? An Australian perspective

BACKGROUND

Within an Australian context, the medium to long-term health impacts of climate change are likely to be wide, varied and amplify many existing disorders and health inequities. How the health system responds to these challenges will be best considered in the context of existing health facilities and services. This paper provides a snapshot of the understanding that Australian health planners have of the potential health impacts of climate change.

METHODS

The first author interviewed (n=16) health service planners from five Australian states and territories using an interpretivist paradigm. All interviews were digitally recorded, key components transcribed and thematically analysed.

RESULTS

Results indicate that the majority of participants were aware of climate change but not of its potential health impacts. Despite this, most planners were of the opinion that they would need to plan for the health impacts of climate change on the community.

CONCLUSION

With the best available evidence pointing towards there being significant health impacts as a result of climate change, now is the time to undertake proactive service planning that address market failures within the health system. If considered planning is not undertaken then Australian health system can only deal with climate change in an expensive ad hoc, crisis management manner. Without meeting the challenges of climate change to the health system head on, Australia will remain unprepared for the health impacts of climate change with negative consequences for the health of the Australian population.

The impact of "unseasonably" warm spring temperatures on acute myocardial infarction hospital admissions in Melbourne, Australia: a city with a temperate climate

The effects of extreme temperatures on human health have been well described. However, the adverse health effects of warm weather that occurs outside the summer period have had little attention. We used daily anomalous AMI morbidity and daily anomalous temperature to determine the impact of "unseasonable" temperature on human health. The "unseasonably" warm weather was attributed to a slow moving high pressure system to the east of Melbourne. No morbidity displacement was noted during either of these periods suggesting that morbidity due to "unseasonable" temperatures is avoidable. An increase in warmer weather during the cooler months of spring may result in increased morbidity, and an alert system based on summer thresholds may not be appropriate for early season heat health warnings. A straightforward alert system based on calculating anomalous temperature from daily weather forecasts may reduce the public health impact of "unseasonably" warm weather.

Extreme heat and cultural and linguistic minorities in Australia: perceptions of stakeholders

Background

Despite acclimatisation to hot weather, many individuals in Australia are adversely affected by extreme heat each summer, placing added pressure on the health sector. In terms of public health, it is therefore important to identify vulnerable groups, particularly in the face of a warming climate. International evidence points to a disparity in heat-susceptibility in certain minority groups, although it is unknown if this occurs in Australia. With cultural diversity increasing, the aim of this study was to explore how migrants from different cultural backgrounds and climate experiences manage periods of extreme heat in Australia.

Methods

A qualitative study was undertaken across three Australian cities, involving interviews and focus groups with key informants including stakeholders involved in multicultural service provision and community members. Thematic analysis and a framework approach were used to analyse the data.

Results

Whilst migrants and refugees generally adapt well upon resettlement, there are sociocultural barriers encountered by some that hinder environmental adaptation to periods of extreme heat in Australia. These barriers include socioeconomic disadvantage and poor housing, language barriers to the access of information, isolation, health issues, cultural factors and lack of acclimatisation. Most often mentioned as being at risk were new arrivals, people in new and emerging communities, and older migrants.

Conclusions

With increasing diversity within populations, it is important that the health sector is aware that during periods of extreme heat there may be disparities in the adaptive capacity of minority groups, underpinned by sociocultural and language-based vulnerabilities in migrants and refugees. These factors need to be considered by policymakers when formulating and disseminating heat health strategies.

Extreme heat awareness and protective behaviors in New York City

Heat waves can be lethal and routinely prompt public warnings about the dangers of heat. With climate change, extreme heat events will become more frequent and intense. However, little is known about public awareness of heat warnings or behaviors during hot weather. Awareness of heat warnings, prevention behaviors, and air conditioning (AC) prevalence and use in New York City were assessed using quantitative and qualitative methods. A random sample telephone survey was conducted in September 2011 among 719 adults and follow-up focus groups were held in winter 2012 among seniors and potential senior caregivers. During summer 2011, 79 % of adults heard or saw a heat warning. Of the 24 % who were seniors or in fair or poor health, 34 % did not own AC or never/rarely used it on hot days. Of this subgroup, 30 % were unaware of warnings, and 49 % stay home during hot weather. Reasons for not using AC during hot weather include disliking AC (29 %), not feeling hot (19 %), and a preference for fans (18 %). Seniors in the focus groups did not perceive themselves to be at risk, and often did not identify AC as an important health protection strategy. While heat warnings are received by most New Yorkers, AC cost, risk perception problems, and a preference for staying home leave many at risk during heat waves. Improving AC access and risk communications will help better protect the most vulnerable during heat waves.

Health impacts of heat in a changing climate: how can emerging science inform urban adaptation planning?

Extreme heat is one of the most important global causes of weather-related mortality, and climate change is leading to more frequent and intense heat waves. Recent epidemiologic findings on heat-related health impacts have reinforced our understanding of mortality impacts of extreme heat and have shown a range of impacts on morbidity outcomes including cardiovascular, respiratory and mental health responses. Evidence is also emerging on temporal trends towards decreasing exposure-response, probably reflecting autonomous population adaptation. Many cities are actively engaged in the development of heat adaptation plans to reduce future health impacts. Epidemiologic research into the evolution of local heat-health responses over time can greatly aid adaptation planning for heat, prevention of adverse health outcomes among vulnerable populations, as well as evaluation of new interventions. Such research will be facilitated by the formation of research partnerships involving epidemiologists, climate scientists, and local stakeholders.

Mortality related to air pollution with the moscow heat wave and wildfire of 2010

BACKGROUND

Prolonged high temperatures and air pollution from wildfires often occur together, and the two may interact in their effects on mortality. However, there are few data on such possible interactions.

METHODS

We analyzed day-to-day variations in the number of deaths in Moscow, Russia, in relation to air pollution levels and temperature during the disastrous heat wave and wildfire of 2010. Corresponding data for the period 2006-2009 were used for comparison. Daily average levels of PM10 and ozone were obtained from several continuous measurement stations. The daily number of nonaccidental deaths from specific causes was extracted from official records. Analyses of interactions considered the main effect of temperature as well as the added effect of prolonged high temperatures and the interaction with PM10.

RESULTS

The major heat wave lasted for 44 days, with 24-hour average temperatures ranging from 24°C to 31°C and PM10 levels exceeding 300 μg/m on several days. There were close to 11,000 excess deaths from nonaccidental causes during this period, mainly among those older than 65 years. Increased risks also occurred in younger age groups. The most pronounced effects were for deaths from cardiovascular, respiratory, genitourinary, and nervous system diseases. Continuously increasing risks following prolonged high temperatures were apparent during the first 2 weeks of the heat wave. Interactions between high temperatures and air pollution from wildfires in excess of an additive effect contributed to more than 2000 deaths.

CONCLUSIONS

Interactions between high temperatures and wildfire air pollution should be considered in risk assessments regarding health consequences of climate change.

The impact of heatwaves on emergency department visits in Brisbane, Australia: a time series study

Introduction

The acute health effects of heatwaves in a subtropical climate and their impact on emergency departments (ED) are not well known. The purpose of this study is to examine overt heat-related presentations to EDs associated with heatwaves in Brisbane.

Methods

Data were obtained for the summer seasons (December to February) from 2000–2012. Heatwave events were defined as two or more successive days with daily maximum temperature ≥34°C (HWD1) or ≥37°C (HWD2). Poisson generalised additive model was used to assess the effect of heatwaves on heat-related visits (International Classification of Diseases (ICD) 10 codes T67 and X30; ICD 9 codes 992 and E900.0).

Results

Overall, 628 cases presented for heat-related illnesses. The presentations significantly increased on heatwave days based on HWD1 (relative risk (RR) = 4.9, 95% confidence interval (CI): 3.8, 6.3) and HWD2 (RR = 18.5, 95% CI: 12.0, 28.4). The RRs in different age groups ranged between 3–9.2 (HWD1) and 7.5–37.5 (HWD2). High acuity visits significantly increased based on HWD1 (RR = 4.7, 95% CI: 2.3, 9.6) and HWD2 (RR = 81.7, 95% CI: 21.5, 310.0). Average length of stay in ED significantly increased by >1 hour (HWD1) and >2 hours (HWD2).

Conclusions

Heatwaves significantly increase ED visits and workload even in a subtropical climate. The degree of impact is directly related to the extent of temperature increases and varies by socio-demographic characteristics of the patients. Heatwave action plans should be tailored according to the population needs and level of vulnerability. EDs should have plans to increase their surge capacity during heatwaves.

The effects of ambient temperature on cerebrovascular mortality: an epidemiologic study in four climatic zones in China

BACKGROUND

Little evidence is available about the association between temperature and cerebrovascular mortality in China. This study aims to examine the effects of ambient temperature on cerebrovascular mortality in different climatic zones in China.

METHOD

We obtained daily data on weather conditions, air pollution and cerebrovascular deaths from five cities (Beijing, Tianjin, Shanghai, Wuhan, and Guangzhou) in China during 2004-2008. We examined city-specific associations between ambient temperature and the cerebrovascular mortality, while adjusting for season, long-term trends, day of the week, relative humidity and air pollution. We examined cold effects using a 1°C decrease in temperature below a city-specific threshold, and hot effects using a 1°C increase in temperature above a city-specific threshold. We used a meta-analysis to summarize the cold and hot effects across the five cities.

RESULTS

Beijing and Tianjin (with low mean temperature) had lower thresholds than Shanghai, Wuhan and Guangzhou (with high mean temperature). In Beijing, Tianjin, Wuhan and Guangzhou cold effects were delayed, while in Shanghai there was no or short induction. Hot effects were acute in all five cities. The cold effects lasted longer than hot effects. The hot effects were followed by mortality displacement. The pooled relative risk associated with a 1°C decrease in temperature below thresholds (cold effect) was 1.037 (95% confidence interval (CI): 1.020, 1.053). The pooled relative risk associated with a 1°C increase in temperature above thresholds (hot effect) was 1.014 (95% CI: 0.979, 1.050).

CONCLUSION

Cold temperatures are significantly associated with cerebrovascular mortality in China, while hot effect is not significant. People in colder climate cities were sensitive to hot temperatures, while people in warmer climate cities were vulnerable to cold temperature.

Development and implementation of South Asia's first heat-health action plan in Ahmedabad (Gujarat, India)

Recurrent heat waves, already a concern in rapidly growing and urbanizing South Asia, will very likely worsen in a warming world. Coordinated adaptation efforts can reduce heat's adverse health impacts, however. To address this concern in Ahmedabad (Gujarat, India), a coalition has been formed to develop an evidence-based heat preparedness plan and early warning system. This paper describes the group and initial steps in the plan's development and implementation. Evidence accumulation included extensive literature review, analysis of local temperature and mortality data, surveys with heat-vulnerable populations, focus groups with health care professionals, and expert consultation. The findings and recommendations were encapsulated in policy briefs for key government agencies, health care professionals, outdoor workers, and slum communities, and synthesized in the heat preparedness plan. A 7-day probabilistic weather forecast was also developed and is used to trigger the plan in advance of dangerous heat waves. The pilot plan was implemented in 2013, and public outreach was done through training workshops, hoardings/billboards, pamphlets, and print advertisements. Evaluation activities and continuous improvement efforts are ongoing, along with plans to explore the program's scalability to other Indian cities, as Ahmedabad is the first South Asian city to address heat-health threats comprehensively.

Heat-related mortality in India: excess all-cause mortality associated with the 2010 Ahmedabad heat wave

INTRODUCTION

In the recent past, spells of extreme heat associated with appreciable mortality have been documented in developed countries, including North America and Europe. However, far fewer research reports are available from developing countries or specific cities in South Asia. In May 2010, Ahmedabad, India, faced a heat wave where the temperatures reached a high of 46.8 °C with an apparent increase in mortality. The purpose of this study is to characterize the heat wave impact and assess the associated excess mortality.

METHODS

We conducted an analysis of all-cause mortality associated with a May 2010 heat wave in Ahmedabad, Gujarat, India, to determine whether extreme heat leads to excess mortality. Counts of all-cause deaths from May 1-31, 2010 were compared with the mean of counts from temporally matched periods in May 2009 and 2011 to calculate excess mortality. Other analyses included a 7-day moving average, mortality rate ratio analysis, and relationship between daily maximum temperature and daily all-cause death counts over the entire year of 2010, using month-wise correlations.

RESULTS

The May 2010 heat wave was associated with significant excess all-cause mortality. 4,462 all-cause deaths occurred, comprising an excess of 1,344 all-cause deaths, an estimated 43.1% increase when compared to the reference period (3,118 deaths). In monthly pair-wise comparisons for 2010, we found high correlations between mortality and daily maximum temperature during the locally hottest "summer" months of April (r = 0.69, p<0.001), May (r = 0.77, p<0.001), and June (r = 0.39, p<0.05). During a period of more intense heat (May 19-25, 2010), mortality rate ratios were 1.76 [95% CI 1.67-1.83, p<0.001] and 2.12 [95% CI 2.03-2.21] applying reference periods (May 12-18, 2010) from various years.

CONCLUSION

The May 2010 heat wave in Ahmedabad, Gujarat, India had a substantial effect on all-cause excess mortality, even in this city where hot temperatures prevail through much of April-June.

Susceptibility to mortality related to temperature and heat and cold wave duration in the population of Stockholm County, Sweden

Background

Ambient temperatures can cause an increase in mortality. A better understanding is needed of how health status and other factors modify the risk associated with high and low temperatures, to improve the basis of preventive measures. Differences in susceptibility to temperature and to heat and cold wave duration are relatively unexplored.

Objectives

We studied the associations between mortality and temperature and heat and cold wave duration, stratified by age and individual and medical factors.

Methods

Deaths among all residents of Stockholm County between 1990 and 2002 were linked to discharge diagnosis data from hospital admissions, and associations were examined using the time stratified case-crossover design. Analyses were stratified by gender, age, pre-existing disease, country of origin, and municipality level wealth, and adjusted for potential confounding factors.

Results

The effect on mortality by heat wave duration was higher for lower ages, in areas with lower wealth, for hospitalized patients younger than age 65. Odds were elevated among females younger than age 65, in groups with a previous hospital admission for mental disorders, and in persons with previous cardiovascular disease. Gradual increases in summer temperatures were associated with mortality in people older than 80 years, and with mortality in groups with a previous myocardial infarction and with chronic obstructive pulmonary disease (COPD) in the population younger than 65 years. During winter, mortality was associated with a decrease in temperature particularly in men and with the duration of cold spells for the population older than 80. A history of hospitalization for myocardial infarction increased the odds associated with cold temperatures among the population older than 65. Previous mental disease or substance abuse increased the odds of death among the population younger than 65.

Conclusion

To increase effectiveness, we suggest preventive efforts should not assume susceptible groups are the same for warm and cold days and heat and cold waves, respectively.

Effect of ambient temperature on Australian northern territory public hospital admissions for cardiovascular disease among indigenous and non-indigenous populations

Hospitalisations are associated with ambient temperature, but little is known about responses in population sub-groups. In this study, heat responses for Indigenous and non-Indigenous people in two age groups were examined for two categories of cardiac diseases using daily hospital admissions from five Northern Territory hospitals (1992-2011). Admission rates during the hottest five per cent of days and the coolest five per cent of days were compared with rates at other times. Among 25-64 year olds, the Indigenous female population was more adversely affected by very hot days than the non-Indigenous female population, with admission rates for ischaemic heart disease (IHD) increasing by 32%. People older than 65 were more sensitive to cold, with non-Indigenous male admissions for heart failure increasing by 64%, and for IHD by 29%. For older Indigenous males, IHD admissions increased by 52% during cold conditions. For older non-Indigenous females, increases in admissions for heart failure were around 50% on these cold days, and 64% for older Indigenous females. We conclude that under projected climate change conditions, admissions for IHD amongst younger Indigenous people would increase in hot conditions, while admissions among elderly people during cold weather may be reduced. The responses to temperature, while showing significant relationships across the Northern Territory, may vary by region. These variations were not explored in this assessment.

Heat waves and health outcomes in Alabama (USA): the importance of heat wave definition

BACKGROUND

A deeper understanding of how heat wave definition affects the relationship between heat exposure and health, especially as a function of rurality, will be useful in developing effective heat wave warning systems.

OBJECTIVE

We compared the relationships between different heat wave index (HI) definitions and preterm birth (PTB) and nonaccidental death (NAD) across urban and rural areas.

METHODS

We used a time-stratified case-crossover design to estimate associations of PTB and NAD with heat wave days (defined using 15 HIs) relative to non-heat wave control days in Alabama, USA (1990-2010). ZIP code-level HIs were derived using data from the North American Land Data Assimilation System. Associations with heat wave days defined using different HIs were compared by bootstrapping. We also examined interactions with rurality.

RESULTS

Associations varied depending on the HI used to define heat wave days. Heat waves defined as having at least 2 consecutive days with mean daily temperatures above the 98th percentile were associated with 32.4% (95% CI: 3.7, 69.1%) higher PTB, and heat waves defined as at least 2 consecutive days with mean daily temperatures above the 90th percentile were associated with 3.7% (95% CI: 1.1, 6.3%) higher NAD. Results suggest that significant positive associations were more common when relative-compared with absolute-HIs were used to define exposure. Both positive and negative associations were found in each rurality stratum. However, all stratum-specific significant associations were positive, and NAD associations with heat waves were consistently positive in urban strata but not in middle or rural strata.

CONCLUSIONS

Based on our findings, we conclude that a relative mean-temperature-only heat wave definition may be the most effective metric for heat wave warning systems in Alabama.

Characterizing urban vulnerability to heat stress using a spatially varying coefficient model

Identifying and characterizing urban vulnerability to heat is a key step in designing intervention strategies to combat negative consequences of extreme heat on human health. This study combines excess non-accidental mortality counts, numerical weather simulations, US Census and parcel data into an assessment of vulnerability to heat in Houston, Texas. Specifically, a hierarchical model with spatially varying coefficients is used to account for differences in vulnerability among census block groups. Socio-economic and demographic variables from census and parcel data are selected via a forward selection algorithm where at each step the remaining variables are orthogonalized with respect to the chosen variables to account for collinearity. Daily minimum temperatures and composite heat indices (e.g. discomfort index) provide a better model fit than other ambient temperature measurements (e.g. maximum temperature, relative humidity). Positive interactions between elderly populations and heat exposure were found suggesting these populations are more responsive to increases in heat.

Estimation and uncertainty analysis of impacts of future heat waves on mortality in the eastern United States

BACKGROUND

Climate change is anticipated to influence heat-related mortality in the future. However, estimates of excess mortality attributable to future heat waves are subject to large uncertainties and have not been projected under the latest greenhouse gas emission scenarios.

OBJECTIVES

We estimated future heat wave mortality in the eastern United States (approximately 1,700 counties) under two Representative Concentration Pathways (RCPs) and investigated sources of uncertainty.

METHODS

Using dynamically downscaled hourly temperature projections for 2057-2059, we projected heat wave days that were defined using four heat wave metrics and estimated the excess mortality attributable to them. We apportioned the sources of uncertainty in excess mortality estimates using a variance-decomposition method.

RESULTS

Estimates suggest that excess mortality attributable to heat waves in the eastern United States would result in 200-7,807 deaths/year (mean 2,379 deaths/year) in 2057-2059. Average excess mortality projections under RCP4.5 and RCP8.5 scenarios were 1,403 and 3,556 deaths/year, respectively. Excess mortality would be relatively high in the southern states and eastern coastal areas (excluding Maine). The major sources of uncertainty were the relative risk estimates for mortality on heat wave versus non-heat wave days, the RCP scenarios, and the heat wave definitions.

CONCLUSIONS

Mortality risks from future heat waves may be an order of magnitude higher than the mortality risks reported in 2002-2004, with thousands of heat wave-related deaths per year in the study area projected under the RCP8.5 scenario. Substantial spatial variability in county-level heat mortality estimates suggests that effective mitigation and adaptation measures should be developed based on spatially resolved data.

Acute and prolonged adverse effects of temperature on mortality from cardiovascular diseases

BACKGROUND

Cardiovascular diseases are the leading causes of death worldwide, especially for developed countries. Elevated mortality from cardiovascular diseases has been shown related to extreme temperature. We thus assessed the risk of mortality from cerebrovascular diseases, heart diseases, and ischemic heart disease (IHD) in relation to temperature profiles in four subtropical metropolitans (Taipei, Taichung, Tainan, and Kaohsiung) from 1994 to 2007 in Taiwan.

METHODS

Distributed lag non-linear models were applied to estimate the cumulative relative risks (RRs) with confidence intervals of cause-specific mortality associated with daily temperature from lag 0 to 20 days, and specific effect of extreme temperature episodes with PM10, NOx, and O3, and other potential confounders controlled. Estimates for cause-specific mortalities were then pooled by random-effect meta-analysis.

RESULTS

Comparing to centered temperature at 27 °C, the cumulative 4-day (lag 0 to 3) risk of mortality was significantly elevated at 31 °C for cerebrovascular diseases (RR = 1.14; 95% CI: 1.00, 1.31) and heart diseases (RR =  1.22; 95% CI: 1.02, 1.46) , but not for IHD (RR =  1.09; 95% CI: 0.99, 1.21). To the other extreme, at 15 °C, the cumulative 21-day (lag 0 to 20) risk of mortality were also remarkably increased for cerebrovascular diseases, heart diseases, and IHD (RRs  =  1.48 with 95% CI: 1.04, 2.12, 2.04 with 95% CI: 1.61, 2.58, and 1.62 with 95% CI: 1.30, 2.01, respectively). Mortality risks for cardiovascular diseases were generally highest on the present day (lag 0) of extreme heat. No particular finding was detected on prolonged extreme temperature event by pooling estimations for cause-specific mortality.

CONCLUSIONS

Low temperature was associated with greater risk of mortality from cardiovascular diseases in comparison with that of high temperature. Adverse effects of extreme temperatures are acute at the beginning of exposure.

Sociogeographic variation in the effects of heat and cold on daily mortality in Japan

BACKGROUND

Ambient temperature affects mortality in susceptible populations, but regional differences in this association remain unclear in Japan. We conducted a time-series study to examine the variation in the effects of ambient temperature on daily mortality across Japan.

METHODS

A total of 731 558 all-age non-accidental deaths in 6 cities during 2002-2007 were analyzed. The association between daily mortality and ambient temperature was examined using distributed lag nonlinear models with Poisson distribution. City-specific estimates were combined using random-effects meta-analysis. Bivariate random-effects meta-regressions were used to examine the moderating effect of city characteristics.

RESULTS

The effect of heat generally persisted for 1 to 2 days. In warmer communities, the effect of cold weather lasted for approximately 1 week. The combined increases in mortality risk due to heat (99th vs 90th percentile of city-specific temperature) and cold (first vs 10th percentile) were 2.21% (95% CI, 1.38%-3.04%) and 3.47% (1.75%-5.21%), respectively. City-specific effects based on absolute temperature changes were more heterogeneous than estimates based on relative changes, which suggests some degree of acclimatization. Northern populations with a cool climate appeared acclimatized to low temperature but were still vulnerable to extreme cold weather. Population density, average income, cost of property rental, and number of nurses appeared to influence variation in heat effect across cities.

CONCLUSIONS

We noted clear regional variation in temperature-related increases in mortality risk, which should be considered when planning preventive measures.