Toward a quantitative estimate of future heat wave mortality under global climate change

Background

Climate change is anticipated to affect human health by changing the distribution of known risk factors. Heat waves have had debilitating effects on human mortality, and global climate models predict an increase in the frequency and severity of heat waves. The extent to which climate change will harm human health through changes in the distribution of heat waves and the sources of uncertainty in estimating these effects have not been studied extensively.

Objectives

We estimated the future excess mortality attributable to heat waves under global climate change for a major U.S. city.

Methods

We used a database comprising daily data from 1987 through 2005 on mortality from all nonaccidental causes, ambient levels of particulate matter and ozone, temperature, and dew point temperature for the city of Chicago, Illinois. We estimated the associations between heat waves and mortality in Chicago using Poisson regression models.

Results

Under three different climate change scenarios for 2081–2100 and in the absence of adaptation, the city of Chicago could experience between 166 and 2,217 excess deaths per year attributable to heat waves, based on estimates from seven global climate models. We noted considerable variability in the projections of annual heat wave mortality; the largest source of variation was the choice of climate model.

Conclusions

The impact of future heat waves on human health will likely be profound, and significant gains can be expected by lowering future carbon dioxide emissions.     

Development of key indicators to quantify the health impacts of climate change on Canadians

Objectives

This study aimed at developing a list of key human health indicators for quantifying the health impacts of climate change in Canada.

Methods

A literature review was conducted in OVID Medline to identify health morbidity and mortality indicators currently used to quantify climate change impacts. Public health frameworks and other studies of climate change indicators were reviewed to identify criteria with which to evaluate the list of proposed key indicators and a rating scale was developed. Total scores for each indicator were calculated based on the rating scale.

Results

A total of 77 health indicators were identified from the literature. After evaluation using the chosen criteria, 8 indicators were identified as the best for use. They include excess daily all-cause mortality due to heat, premature deaths due to air pollution (ozone and particulate matter 2.5), preventable deaths from climate change, disability-adjusted life years lost from climate change, daily all-cause mortality, daily non-accidental mortality, West Nile Disease incidence, and Lyme borreliosis incidence.

Conclusions

There is need for further data and research related to health effect quantification in the area of climate change.     

The 2006 California Heat Wave: Impacts on Hospitalizations and Emergency Department Visits

Background

Climate models project that heat waves will increase in frequency and severity. Despite many studies of mortality from heat waves, few studies have examined morbidity.

Objectives

In this study we investigated whether any age or race/ethnicity groups experienced increased hospitalizations and emergency department (ED) visits overall or for selected illnesses during the 2006 California heat wave.

Methods

We aggregated county-level hospitalizations and ED visits for all causes and for 10 cause groups into six geographic regions of California. We calculated excess morbidity and rate ratios (RRs) during the heat wave (15 July to 1 August 2006) and compared these data with those of a reference period (8–14 July and 12–22 August 2006).

Results

During the heat wave, 16,166 excess ED visits and 1,182 excess hospitalizations occurred statewide. ED visits for heat-related causes increased across the state [RR = 6.30; 95% confidence interval (CI), 5.67–7.01], especially in the Central Coast region, which includes San Francisco. Children (0–4 years of age) and the elderly (≥ 65 years of age) were at greatest risk. ED visits also showed significant increases for acute renal failure, cardiovascular diseases, diabetes, electrolyte imbalance, and nephritis. We observed significantly elevated RRs for hospitalizations for heat-related illnesses (RR = 10.15; 95% CI, 7.79–13.43), acute renal failure, electrolyte imbalance, and nephritis.

Conclusions

The 2006 California heat wave had a substantial effect on morbidity, including regions with relatively modest temperatures. This suggests that population acclimatization and adaptive capacity influenced risk. By better understanding these impacts and population vulnerabilities, local communities can improve heat wave preparedness to cope with a globally warming future.     

Heat waves in the United States: mortality risk during heat waves and effect modification by heat wave characteristics in 43 U.S. communities

Background

Devastating health effects from recent heat waves, and projected increases in frequency, duration, and severity of heat waves from climate change, highlight the importance of understanding health consequences of heat waves.

Objectives

We analyzed mortality risk for heat waves in 43 U.S. cities (1987–2005) and investigated how effects relate to heat waves’ intensity, duration, or timing in season.

Methods

Heat waves were defined as ≥ 2 days with temperature ≥ 95th percentile for the community for 1 May through 30 September. Heat waves were characterized by their intensity, duration, and timing in season. Within each community, we estimated mortality risk during each heat wave compared with non-heat wave days, controlling for potential confounders. We combined individual heat wave effect estimates using Bayesian hierarchical modeling to generate overall effects at the community, regional, and national levels. We estimated how heat wave mortality effects were modified by heat wave characteristics (intensity, duration, timing in season).

Results

Nationally, mortality increased 3.74% [95% posterior interval (PI), 2.29–5.22%] during heat waves compared with non-heat wave days. Heat wave mortality risk increased 2.49% for every 1°F increase in heat wave intensity and 0.38% for every 1-day increase in heat wave duration. Mortality increased 5.04% (95% PI, 3.06–7.06%) during the first heat wave of the summer versus 2.65% (95% PI, 1.14–4.18%) during later heat waves, compared with non-heat wave days. Heat wave mortality impacts and effect modification by heat wave characteristics were more pronounced in the Northeast and Midwest compared with the South.

Conclusions

We found higher mortality risk from heat waves that were more intense or longer, or those occurring earlier in summer. These findings have implications for decision makers and researchers estimating health effects from climate change.     

Distribution and trends in mesothelioma mortality in Italy from 1974 to 2006

Purpose

Using the epidemiological data of pleural cancer mortality, the authors estimated time trends and distribution of malignant mesothelioma in Italy during the period 1974–2006.

Methods

To describe temporal trends of the standardized mortality ratios (SMRs) in all the 20 Italian regions, we applied the Joinpoint Regression Model, developed by the National Cancer Institute (USA). The 107 provincial SMRs are represented on maps by using the Arcview GIS software (version 3.2).

Results

The high values from mesothelioma mortality in construction and shipbuilding sectors, previously reported, are confirmed by our analyses. Furthermore, data show that the annual percentage change is still growing: statistically significant increments in time trends are observed for 11 of 20 Italian regions. Of additional concern has been the identification of changes in 9 of 20 trends partially due to the misdiagnosis in the past.

Conclusions

Given the long latency of mesothelioma, preventive and legal measures with the ban of asbestos in Italy since 1992 are still not giving effects on mesothelioma mortality trends.     

Changes in population susceptibility to heat and cold over time: assessing adaptation to climate change

Background

In the context of a warming climate and increasing urbanisation (with the associated urban heat island effect), interest in understanding temperature related health effects is growing. Previous reviews have examined how the temperature-mortality relationship varies by geographical location. There have been no reviews examining the empirical evidence for changes in population susceptibility to the effects of heat and/or cold over time. The objective of this paper is to review studies which have specifically examined variations in temperature related mortality risks over the 20^th and 21^st centuries and determine whether population adaptation to heat and/or cold has occurred.

Methods

We searched five electronic databases combining search terms for three main concepts: temperature, health outcomes and changes in vulnerability or adaptation. Studies included were those which quantified the risk of heat related mortality with changing ambient temperature in a specific location over time, or those which compared mortality outcomes between two different extreme temperature events (heatwaves) in one location.

Results

The electronic searches returned 9183 titles and abstracts, of which eleven studies examining the effects of ambient temperature over time were included and six studies comparing the effect of different heatwaves at discrete time points were included. Of the eleven papers that quantified the risk of, or absolute heat related mortality over time, ten found a decrease in susceptibility over time of which five found the decrease to be significant. The magnitude of the decrease varied by location. Only two studies attempted to quantitatively attribute changes in susceptibility to specific adaptive measures and found no significant association between the risk of heat related mortality and air conditioning prevalence within or between cities over time. Four of the six papers examining effects of heatwaves found a decrease in expected mortality in later years. Five studies examined the risk of cold. In contrast to the changes in heat related mortality observed, only one found a significant decrease in cold related mortality in later time periods.

Conclusions

There is evidence that across a number of different settings, population susceptibility to heat and heatwaves has been decreasing. These changes in heat related susceptibility have important implications for health impact assessments of future heat related risk. A similar decrease in cold related mortality was not shown. Adaptation to heat has implications for future planning, particularly in urban areas, with anticipated increases in temperature due to climate change.

     

Heat-related mortality risk model for climate change impact projection

Objectives

We previously developed a model for projection of heat-related mortality attributable to climate change. The objective of this paper is to improve the fit and precision of and examine the robustness of the model.

Methods

We obtained daily data for number of deaths and maximum temperature from respective governmental organizations of Japan, Korea, Taiwan, the USA, and European countries. For future projection, we used the Bergen climate model 2 (BCM2) general circulation model, the Special Report on Emissions Scenarios (SRES) A1B socioeconomic scenario, and the mortality projection for the 65+-year-old age group developed by the World Health Organization (WHO). The heat-related excess mortality was defined as follows: The temperature–mortality relation forms a V-shaped curve, and the temperature at which mortality becomes lowest is called the optimum temperature (OT). The difference in mortality between the OT and a temperature beyond the OT is the excess mortality. To develop the model for projection, we used Japanese 47-prefecture data from 1972 to 2008. Using a distributed lag nonlinear model (two-dimensional nonparametric regression of temperature and its lag effect), we included the lag effect of temperature up to 15 days, and created a risk function curve on which the projection is based. As an example, we perform a future projection using the above-mentioned risk function. In the projection, we used 1961–1990 temperature as the baseline, and temperatures in the 2030s and 2050s were projected using the BCM2 global circulation model, SRES A1B scenario, and WHO-provided annual mortality. Here, we used the “counterfactual method” to evaluate the climate change impact; For example, baseline temperature and 2030 mortality were used to determine the baseline excess, and compared with the 2030 excess, for which we used 2030 temperature and 2030 mortality. In terms of adaptation to warmer climate, we assumed 0 % adaptation when the OT as of the current climate is used and 100 % adaptation when the OT as of the future climate is used. The midpoint of the OTs of the two types of adaptation was set to be the OT for 50 % adaptation.

Results

We calculated heat-related excess mortality for 2030 and 2050.

Conclusions

Our new model is considered to be better fit, and more precise and robust compared with the previous model.     

The effect of heat waves on mental health in a temperate Australian city

Objective

The goal of this study was to identify mental, behavioral, and cognitive disorders that may be triggered or exacerbated during heat waves, predisposing individuals to heat-related morbidity and mortality.

Design

Using health outcome data from Adelaide, South Australia, for 1993–2006, we estimated the effect of heat waves on hospital admissions and mortalities attributed to mental, behavioral, and cognitive disorders. We analyzed data using Poisson regression accounting for overdispersion and controlling for season and long-term trend, and we performed threshold analysis using hockey stick regression.

Results

Above a threshold of 26.7°C, we observed a positive association between ambient temperature and hospital admissions for mental and behavioral disorders. Compared with non–heat-wave periods, hospital admissions increased by 7.3% during heat waves. Specific illnesses for which admissions increased included organic illnesses, including symptomatic mental disorders; dementia; mood (affective) disorders; neurotic, stress related, and somatoform disorders; disorders of psychological development; and senility. Mortalities attributed to mental and behavioral disorders increased during heat waves in the 65- to 74-year age group and in persons with schizophrenia, schizotypal, and delusional disorders. Dementia deaths increased in those up to 65 years of age.

Conclusion

Our results suggest that episodes of extreme heat pose a salient risk to the health and well-being of the mentally ill.Relevance to Clinical or Professional Practice: Improvements in the management and care of the mentally ill need to be addressed to avoid an increase in psychiatric morbidity and mortality as heat waves become more frequent.     

Attribution of mortality to the urban heat island during heatwaves in the West Midlands,UK

Background

The Urban Heat Island (UHI) effect describes the phenomenon whereby cities are generally warmer than surrounding rural areas. Traditionally, temperature monitoring sites are placed outside of city centres, which means that point measurements do not always reflect the true air temperature of urban centres, and estimates of health impacts based on such data may under-estimate the impact of heat on public health. Climate change is likely to exacerbate heatwaves in future, but because climate projections do not usually include the UHI, health impacts may be further underestimated. These factors motivate a two-dimensional analysis of population weighted temperature across an urban area, for heat related health impact assessments, since populations are typically densest in urban centres, where ambient temperatures are highest and the UHI is most pronounced. We investigate the sensitivity of health impact estimates to the use of population weighting and the inclusion of urban temperatures in exposure data.

Methods

We quantify the attribution of the UHI to heat related mortality in the West Midlands during the heatwave of August 2003 by comparing health impacts based on two modelled temperature simulations. The first simulation is based on detailed urban land use information and captures the extent of the UHI, whereas in the second simulation, urban land surfaces have been replaced by rural types.

Results and conclusions

The results suggest that the UHI contributed around 50 % of the total heat-related mortality during the 2003 heatwave in the West Midlands. We also find that taking a geographical, rather than population-weighted, mean of temperature across the regions under-estimates the population exposure to temperatures by around 1 °C, roughly equivalent to a 20 % underestimation in mortality. We compare the mortality contribution of the UHI to impacts expected from a range of projected temperatures based on the UKCP09 Climate Projections. For a medium emissions scenario, a typical heatwave in 2080 could be responsible for an increase in mortality of around 3 times the rate in 2003 (278 vs. 90 deaths) when including changes in population, population weighting and the UHI effect in the West Midlands, and assuming no change in population adaptation to heat in future.

     

Air pollution exposure estimation using dispersion modelling and continuous monitoring data in a prospective birth cohort study in the Netherlands

Background

High temperature and humidity conditions are associated with short-term elevations in the mortality rate in many United States cities. Previous research has quantified this relationship in an aggregate manner over large metropolitan areas, but within these areas the response may differ based on local-scale variability in climate, population characteristics, and socio-economic factors.

Methods

We compared the mortality response for 48 Zip Code Tabulation Areas (ZCTAs) comprising Philadelphia County, PA to determine if certain areas are associated with elevated risk during high heat stress conditions. A randomization test was used to identify mortality exceedances for various apparent temperature thresholds at both the city and local scale. We then sought to identify the environmental, demographic, and social factors associated with high-risk areas via principal components regression.

Results

Citywide mortality increases by 9.3% on days following those with apparent temperatures over 34°C observed at 7:00 p.m. local time. During these conditions, elevated mortality rates were found for 10 of the 48 ZCTAs concentrated in the west-central portion of the County. Factors related to high heat mortality risk included proximity to locally high surface temperatures, low socioeconomic status, high density residential zoning, and age.

Conclusions

Within the larger Philadelphia metropolitan area, there exists statistically significant fine-scale spatial variability in the mortality response to high apparent temperatures. Future heat warning systems and mitigation and intervention measures could target these high risk areas to reduce the burden of extreme weather on summertime morbidity and mortality.     

Anpassungsbedarf an den Klimawandel zur Pr?vention gesundheitlicher Risiken

Background

Changes in global climate as well as changes in the German climate have been observed in recent years. Those changes are probably due to anthropogenic greenhouse gas emissions. Even if human greenhouse gas emissions are significantly reduced, air temperature will continue to rise.

Results

Four regional climate models were analysed for Germany. These models project an increase in mean annual air temperature between 1 and 2°C for the middle of the twenty-first century and an increase between 2.5 and 4°C for the end of this century with respect to the mean annual air temperature of the period 1971?C2000.

Conclusion

This change in climate also affects human health. More and more intense heat waves could for instance increase the risk of heat-related morbidity and mortality. In order to keep the impacts of climate change for humans and the environment as small as possible, there is an urgent need to adapt to the changing climate.     

An updated historical cohort mortality study of workers exposed to asbestos in a refitting shipyard, 1947�C2007

Purpose

To evaluate the long-term health effects of occupational asbestos exposure, an updated historical cohort mortality study of workers at a refitting shipyard was undertaken.

Methods

The cohort consisted of 249 male ship repair workers (90 laggers, 159 boiler repairers). To determine relative excess mortality, standardized mortality ratios (SMRs) were calculated using mortality rates among the Japanese male population. Mortality follow-up of study subjects was performed for the period from 1947 till the end of 2007.

Results

We identified the vital status of 87 (96.7%) laggers and 150 (94.3%) boiler repairers. Of these, 63 (72.4%) and 95 (63.3%), respectively, died. Laggers, who had handled asbestos materials directly, showed a significantly elevated SMR of 2.64 (95% confidence interval [CI]: 1.06?C5.44) for lung cancer and 2.49 (95% CI: 1.36?C4.18) for nonmalignant respiratory diseases. Boiler repairers, who had many opportunities for secondary exposure to asbestos and a few for direct exposure, showed no significant elevation in SMR for lung cancer but a significantly elevated SMR of 1.78 (95% CI: 1.06?C2.81) for nonmalignant respiratory diseases. In an analysis according to duration of employment, there was a significantly elevated SMR of nonmalignant respiratory diseases in the longer working years group. Among workers from both jobs, no deaths caused by mesothelioma in addition to those in the original study were found and no subject died from larynx cancer.

Conclusion

This updated study confirmed a significant excess of asbestos-related mortality from diseases such as lung cancer and nonmalignant respiratory diseases among workers in a refitting shipyard in Japan.     

Socio-economic disparities in mortality due to pandemic influenza in England

Objectives

This study examines variations in mortality between socio-economic groups due to the pandemic Influenza (H1N1) 2009 virus in England.

Methods

We established a system to identify all deaths related to pandemic (H1N1) 2009 influenza. We collected the postcode of every individual who died, and through this determined the socio-economic deprivation, urban–rural characteristics and region of their residence. Across England, we were therefore able to examine how mortality rates varied by socio-economic group, between urban and rural areas, and between regions.

Results

People in the most deprived quintile of England’s population had an age and sex-standardised mortality rate three times that experienced by the least deprived quintile (RR?=?3.1, 95% CI 2.2–4.4). Mortality was also higher in urban areas than in rural areas (RR?=?1.7, 95% CI 1.2–2.3). Mortality rates were similar between regions of the country.

Conclusion

Tackling socio-economic health inequalities is a central concept within public health, but has not always been a part of emergency preparedness plans. These data demonstrate the opportunity to reduce the overall impact and narrow inequalities by considering socio-economic disparities in future pandemic planning.     

Evaluating the effectiveness of heat warning systems: systematic review of epidemiological evidence

Objectives

To review the existing research on the effectiveness of heat warning systems (HWSs) in saving lives and reducing harm.

Methods

A systematic search of major databases was conducted, using “heat, heatwave, high temperature, hot temperature, OR hot climate” AND “warning system”.

Results

Fifteen articles were retrieved. Six studies asserted that fewer people died of excessive heat after HWS implementation. HWS was associated with reduction in ambulance use. One study estimated the benefits of HWS to be $468 million for saving 117 lives compared to $210,000 costs of running the system. Eight studies showed that mere availability of HWS did not lead to behavioral changes. Perceived threat of heat dangers to self/others was the main factor related to heeding warnings and taking proper actions. However, costs and barriers associated with taking protective actions, such as costs of running air conditioners, were of significant concern particularly to the poor.

Conclusions

Research in this area is limited. Prospective designs applying health behavior theories should establish whether HWS can produce the health benefits they are purported to achieve by identifying the target vulnerable groups.     

Mortality gradient across the labour market core–periphery structure: a 13-year mortality follow-up study in north-eastern France

Purpose

This study explores mortality related to temporary employment, about which very little is known to date.

Methods

In 1996, a health survey was carried out in the French region of Lorraine, and all members of 8,000 randomly chosen households were followed up for mortality over a 13-year period. Mortality of subjects in relation to their employment situation at baseline was analysed using a Cox survival regression.

Results

In comparison with permanent workers, for unemployed men, we found age and occupation-adjusted hazard ratios (HR) of 4.1 for all-causes of death and 3.9 for non-violent causes, and for male temporary workers a HR of 2.2 for both all-causes and non-violent causes of death. Bad health, tobacco smoking and alcohol misuse explained 17 % of the excess risk for the unemployed and 41 % of that for temporary workers.

Conclusion

The observation of large mortality inequalities across the labour market core–periphery structure has important policy implications, particularly in terms of prevention focused on unhealthy behaviours among male unemployed and temporary workers.     

Predictors of 3-year mortality in subjects over 95 years of age. The nonasantfeliu study

Objectives

To examine the survival rates of subjects aged 95 or over after a follow-up period of 3 years, and to determine predictive factors for mortality risk.

Design

A prospective cohort study.

Setting

A community-based study.

Participants

Forty-eight subjects aged 95 or over.

Measurements

Sociodemographic data, Barthel Index, Lawton-Brody Index, Spanish version of the Mini-Mental State Examination, short version of the Mini Nutritional Assessment, comorbidity (Charlson Index), and prevalent chronic diseases were evaluated. Patients who died were compared with the rest.

Results

Thirty-six deaths (75%) were recorded during follow-up. The Cox multivariate analysis showed that lower Barthel Index scores and a history of heart failure were independently associated with long-term mortality.

Conclusions

In subjects aged 95 or over, poor functional status and history of heart failure were the two independent risk factors for 3-year mortality.     

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

Purpose

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

Methods

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

Results

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

Conclusions

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

The validity of a patient-reported adverse drug event questionnaire using different recall periods

Purpose

To assess the validity of a patient-reported adverse drug events (ADEs) questionnaire with a 3-month or 4-week recall period.

Methods

Patients receiving at least one oral glucose-lowering drug were asked to report potential ADEs they experienced related to any drug in a daily diary for a 3-month period. Thereafter, they completed the ADE questionnaire with either a 3-month or 4-week recall period. The validity was assessed by comparing ADEs reported in each version with those reported in the diary at class level and at specific ADE level. At class level, a comparison was made using (1) primary system organ classes (SOCs) of the medical dictionary for regulatory activities and (2) other related SOCs. Sensitivity and positive predictive value (PPV) were calculated.

Results

Each version of the questionnaire was completed by 39 patients. In the 3-month group, 21 patients reported 70 ADEs in the diary. In the 4-week group, six patients reported seven ADEs in the last 4 weeks of the diary. Sensitivity to assess ADEs at primary SOC was low for both recall groups (33 %). PPV was 51 and 10 % for, respectively, the 3-month and 4-week group. Taking other related SOCs into account slightly increased the sensitivity for the 3-month group (38%). Sensitivity of reporting the same ADE was 41 and 43 % for, respectively, the 3-month and 4-week group.

Conclusions

Regardless of the recall period and level of comparison, the validity for assessing ADEs was low with the patient-reported ADE questionnaire. Further refinement is needed to improve the validity.     

Methods to Estimate Acclimatization to Urban Heat Island Effects on Heat- and Cold-Related Mortality

Background:

Investigators have examined whether heat mortality risk is increased in neighborhoods subject to the urban heat island (UHI) effect but have not identified degrees of difference in susceptibility to heat and cold between cool and hot areas, which we call acclimatization to the UHI.

Objectives:

We developed methods to examine and quantify the degree of acclimatization to heat- and cold-related mortality in relation to UHI anomalies and applied these methods to London, UK.

Methods:

Case–crossover analyses were undertaken on 1993–2006 mortality data from London UHI decile groups defined by anomalies from the London average of modeled air temperature at a 1-km grid resolution. We estimated how UHI anomalies modified excess mortality on cold and hot days for London overall and displaced a fixed-shape temperature-mortality function (“shifted spline” model). We also compared the observed associations with those expected under no or full acclimatization to the UHI.

Results:

The relative risk of death on hot versus normal days differed very little across UHI decile groups. A 1°C UHI anomaly multiplied the risk of heat death by 1.004 (95% CI: 0.950, 1.061) (interaction rate ratio) compared with the expected value of 1.070 (1.057, 1.082) if there were no acclimatization. The corresponding UHI interaction for cold was 1.020 (0.979, 1.063) versus 1.030 (1.026, 1.034) (actual versus expected under no acclimatization, respectively). Fitted splines for heat shifted little across UHI decile groups, again suggesting acclimatization. For cold, the splines shifted somewhat in the direction of no acclimatization, but did not exclude acclimatization.

Conclusions:

We have proposed two analytical methods for estimating the degree of acclimatization to the heat- and cold-related mortality burdens associated with UHIs. The results for London suggest relatively complete acclimatization to the UHI effect on summer heat–related mortality, but less clear evidence for cold–related mortality.

Citation:

Milojevic A, Armstrong BG, Gasparrini A, Bohnenstengel SI, Barratt B, Wilkinson P. 2016. Methods to estimate acclimatization to urban heat island effects on heat- and cold-related mortality. Environ Health Perspect 124:1016–1022; http://dx.doi.org/10.1289/ehp.1510109