Temperature related mortality and ambulance service interventions during the heat waves of 2003 in Ticino (Switzerland)

Summary. Objectives This study investigates a potential increase in mortality and in the demand for ambulance emergency services among the elderly in particular, in Ticino in the summer of 2003. Methods Mortality rates and emergency ambulance interventions rates were compared with records from the previous years. We considered the whole population, aged 65 and over, as well as 75 and over. Results The 2003 mortality in the population was not signifi cantly different from the previous years. The number of deaths among the elderly showed a small but significant deviation from the expected values during the first heat wave in June 2003, with no significant impact on the seasonal results. The number of ambulance service interventions was larger than during the previous years. Conclusion These results are consistent with findings in other studies. The heat waves (especially in June), were correlated with a higher number of ambulance callouts. In addition to some geographic, climatic, and social factors that had a protective impact, the response of the emergency services is likely to have contributed to a certain reduction in mortality. Submitted: 29 October 2004; Accepted: 29 August 2005     

General and specific mortality among the elderly during the 2003 heat wave in Genoa (Italy)

The effects of heat waves on health can be serious for elderly persons, especially those in urban areas. We investigated in-depth the mortality excess during the 2003 heat wave among elderly persons (>74 years) in the City of Genoa (Italy). The excess in general mortality was calculated for the period July 16-August 31, as the ratio of observed to expected deaths. To evaluate "harvesting", we compared observed and expected mortality in the period September 2003-April 2004. We also studied the relationship between mortality and climatic conditions considering daily maximum temperature and Humidex discomfort degrees, as well as "lag-time". For cause-specific mortality, we considered all pathologies reported on the death certificate. The excess in general mortality was significant and was greatest in the first half of August. During Summer 2003, in Genoa the climatic conditions (described in terms of maximum temperature and Humidex Index) were extremely hot; regarding lag-time, the greatest correlation between the number of observed deaths and the maximum temperature values was observed for the three preceding days (rho=0.568; significance level<0.01). The prominent causes of death, for which an excess was observed, were cerebrovascular diseases, severe respiratory diseases, severe renal diseases, dementia; moreover, certain pathologic conditions and symptoms, usually not lethal, were also frequent causes of death (e.g., hypovolemia, hyperpyrexia, decubitus ulcers and immobilization syndrome). The results of this study confirm the relationship between the heat waves and death among elderly, stressing that, because of their poorer physical health and the prevalence of cognitive disturbances that hinder risk perception, it is necessary to properly care for them during heat waves.     

Excess mortality related to the August 2003 heat wave in France

Objectives: From August 1st to 20th, 2003, the mean maximum temperature in France exceeded the seasonal norm by 11–12°C on nine consecutive days. A major increase in mortality was then observed, which main epidemiological features are described herein. Methods: The number of deaths observed from August to November 2003 in France was compared to those expected on the basis of the mortality rates observed from 2000 to 2002 and the 2003 population estimates. Results: From August 1st to 20th, 2003, 15,000 excess deaths were observed. From 35 years age, the excess mortality was marked and increased with age. It was 15% higher in women than in men of comparable age as of age 45 years. Excess mortality at home and in retirement institutions was greater than that in hospitals. The mortality of widowed, single and divorced subjects was greater than that of married people. Deaths directly related to heat, heatstroke, hyperthermia and dehydration increased massively. Cardiovascular diseases, ill-defined morbid disorders, respiratory diseases and nervous system diseases also markedly contributed to the excess mortality. The geographic variations in mortality showed a clear age-dependent relationship with the number of very hot days. No harvesting effect was observed. Conclusions: Heat waves must be considered as a threat to European populations living in climates that are currently temperate. While the elderly and people living alone are particularly vulnerable to heat waves, no segment of the population may be considered protected from the risks associated with heat waves.A. Fouillet and G. Rey have equally contributed to this work.     

Socioeconomic position and excess mortality during the heat wave of 2003 in Barcelona

The objective of this study is to determine whether the excess of mortality which occurred in Barcelona during the summer of 2003 was dependent on age, gender and educational level. We included all deaths among Barcelona residents 20 years of age and older that occurred in the city during the months of June, July and August of 2003 and also during the same months of the five preceding years. Poisson regression models were fitted to obtain the risk of death in 2003 with respect to the period 1998–2002. The relative risk (RR) of mortality during the summer of 2003, compared to the summers of the previous 5 years, was higher for women than for men and among older ages. Although an increase among women was observed in all educational groups, in some age groups the increase was larger for people with less than primary education. The excess number of deaths was higher for those with less education. These results suggest that age, gender and educational level were important determinants of excess mortality in the 2003 Barcelona heat wave.     

Epidemiologic study of mortality during the Summer 2003 heat wave in Italy

INTRODUCTION: It is widely recognized that extreme climatic conditions during summer months may constitute a major public health threat. Owing to what is called the "urban heat island effect," as well as to the consequences of heat waves on health, individuals living in cities have an elevated risk of death when temperature and humidity are high compared to those living in suburban and rural areas. Studies on heat wave-related mortality have further demonstrated that the greatest increases in mortality occur in the elderly. Following the unusually hot summer of 2003 and the dramatic news from neighboring countries such as France, the Italian Minister of Health requested the Istituto Superiore di Sanita-Bureau of Statistics to undertake an epidemiologic study of mortality in Italy during Summer 2003 to investigate whether there had been an excess of deaths, with a particular focus on the elderly population. MATERIALS AND METHODS: Communal offices, which maintain vital statistics, were asked for the individual records of death of residents registered daily during the period 1 June-31 August 2003 and during the same period of 2002 for each of the 21 capitals of the Italian regions. As it was necessary to obtain mortality data quickly from many municipalities and to make the analysis as soon as possible, the method adopted was comparison of mortality counts during the heat wave with figures observed during the same period of the previous year. RESULTS: Compared with 2002, between 1 June and 31 August 2003, there was an overall increase in mortality of 3134 (from 20,564 to 23,698). The greatest increase was among the elderly; 2876 deaths (92%) occurred among people aged 75 years and older, a more than one-fifth increase (21.3%, from 13.517 to 16.393%). The highest increases were observed in the northwestern cities, which are generally characterized by cold weather, and in individuals 75 years and older: Turin (44.9%), Trento (35.2%), Milan (30.6%), and Genoa (22.2%). Of note are also the increases observed in two southern cities, L'Aquila (24.7%) and Potenza (25.4%), which are located, respectively, at 700 and 800 m above see level. For Bari and Campobasso, both in the South, with a typically hot summer climate, the increase during the last 15 days of August was 186.2 and 450%, respectively. CONCLUSIONS: The relationship between mortality and discomfort due to climatic conditions as well as the short lag time give a clear public health message: preventive, social, and health care actions must be administered to the elderly and the frail to avoid excess deaths during heat waves.     

The impact of heat islands on mortality in Paris during the August 2003 heat wave

Background: Heat waves have a drastic impact on urban populations, which could increase with climate change.Objectives: We evaluated new indicators of elderly people’s exposure to heat in Paris, from a public health prevention perspective, using satellite thermal images.Methods: We used a time series of 61 images from the satellites of the National Oceanic and Atmospheric Administration’s (NOAA) Advanced Very High Resolution Radiometer (AVHRR) taken from 1 to 13 August 2003 to produce thermal indicators of minimum, maximum, and mean surface temperatures and diurnal temperature amplitude, with different lags between the meteorological data and the health impact. Health data came from a case–control study involving 241 people ≥ 65 years of age who died in the city of Paris or the nearby suburban area of Val-de-Marne during the August 2003 heat wave, and 241 controls who were matched to cases on age, sex, and residential zone. For each person, we integrated the thermal indicators in a conditional logistic regression model, adjusted for age and other potential confounders. We computed odds ratios (ORs) comparing the 90th and 50th percentiles of the temperature differences between cases and controls for various indicators.Results: Mortality risk was significantly associated with exposure for two indicators: minimum temperatures averaged for 1–13 August [for a 0.41°C increase, OR = 2.17; 95% confidence interval (CI): 1.14, 4.16] and minimum temperature averaged on the day of death and the 6 preceding days (for a 0.51°C increase: OR = 2.24; 95% CI: 1.03, 4.87).Conclusions: Our results support the influence of night temperatures on the health impact of heat waves in urban areas. Urban heat exposure indicators based on satellite imagery have the potential to identify areas with higher risk of death, which could inform intervention decisions by key stakeholders.     

Rhipicephalus ticks infected with Rickettsia and Coxiella in Southern Switzerland (Canton Ticino).

Ticks of the Rhipicephalus sanguineus species complex may be vector of various pathogens including Rickettsia conorii (the etiological agent of the Mediterranean spotted fever) and Coxiella burnetii (cause of the Query (Q) fever). R. sanguineus ticks have been imported in several parts of central and northern Europe, especially in environments such as kennels and houses providing the appropriate microclimatic conditions and the blood source necessary for their survival. Since 1940 these ticks have occasionally been recorded in Switzerland. In Ticino (the southern part of Switzerland), they have been reported since 1980 and their probable establishment in this area has been suggested in the '90s. By means of PCR and direct sequencing, we tested the identity of these ticks (using 12S rDNA gene) and the occurrence of Rickettsia spp. (using 16S rDNA, gltA and OmpA genes) as well as Coxiella sp. (using 16S rDNA). The results indicated that in Ticino, two different tick species coexist, i.e. R. sanguineus sensu stricto and Rhipicephalus turanicus. A few individuals of R. sanguineus sensu stricto are infected with Rickettsia massiliae/Bar29, which are strains of unknown pathogenicity. Coxiella sp., an endosymbiont of Rhipicephalus ticks, has also been identified in both tick species. Due to climatic changes towards global warming, imported tick species may therefore adapt to new area and might be considered as epidemiological markers for a number of infectious agents transmitted by them.     

Distribution and prevalence of Borrelia burgdorferi sensu lato in Ixodes ricinus ticks of canton Ticino (Switzerland)

Free-living Ixodes ricinus ticks were collected from 12 different sites of canton Ticino, south of the Alps (Switzerland). Each tick was examined for the presence of Borrelia burgdorferi sensu lato (sl), the etiologic agent of Lyme borreliosis using direct fluorescent antibody assay, and isolation of the bacteria. Borreliae were characterized by PCR followed by RFLP. The abundance and infection rates of I. ricinus ticks varied greatly between the areas. Two localities were found free of Borrelia. The prevalence of infected ticks ranged from 5 to 19%. Most ticks (96%) were found infected by <50 spirochetes. Three B. burgdorferi sl species were successfully isolated: B. garinii dominated, followed by B. lusitaniae and B. valaisiana. Additionally, a mixed infection with B. garinii and B. valaisiana was observed. The distribution of the various Borrelia species in the different areas was heterogeneous. This is the first report of the presence of B. lusitaniae in I. ricinus in Switzerland.     

The impact of major heat waves on all-cause and cause-specific mortality in France from 1971 to 2003

Objectives The aim of the study was to identify the major heat waves (HW) that occurred in France from 1971 to 2003 and describe their impact on all-cause and cause-specific mortality. Methods Heat waves were defined as periods of at least three consecutive days when the maximum and the minimum temperature, averaged over the whole France, were simultaneously greater than their respective 95th percentile. The underlying causes of death were regrouped into 18 categories. Heatstroke, hyperthermia and dehydration were assigned to the “heat-related causes” (HRC) category. The numbers of deaths observed (O) during the identified HW were compared to those expected (E) on the basis of the mortality rates reported for the three preceding years. Results Six HW were identified from the period 1971 to 2003. They were associated with great excess mortality (from 1,300 to 13,700 deaths). The observations are compatible with a moderate harvesting effect for four of the six HW. The mortality ratios increased with age for subjects aged over 55 years and were higher for women than for men over 75 years. For the six HW, the excess mortality was significant for almost all the causes of death: (1) the greatest excess mortality (O–E) were observed for cardiovascular diseases, neoplasms, respiratory system diseases, HRC, ill-defined conditions and injury and poisoning, and (2) the mortality ratios (O/E) were highest for HRC, respiratory diseases, nervous system diseases, mental disorders, infectious diseases, and endocrine and nutritional diseases. Conclusions Heat waves associated with excess mortality are not rare events in this temperate-climate country. The excess mortality is much greater than HRC mortality. Some populations are particularly vulnerable to HW: the elderly, women and people with some specific diseases. However, no segment of the population may be considered protected from the risks associated with HW.     

Effects of temperature and ozone on daily mortality during the August 2003 heat wave in France

During the summer of 2003, Europe experienced a heat wave that lasted almost 2 weeks in which high temperatures were accompanied by exceptionally high ozone levels. Unfortunately, few studies have examined the effects of temperature and ozone simultaneously. The authors use constrained distributed lag models to estimate the effects of daily temperature and peak ozone on mortality in 12 French cities during the heat wave and to estimate the deaths attributable to each component. Elevated minimum and maximum temperature and peak ozone all increase mortality, with substantial interaction effects between temperature and ozone. Researchers expect extreme weather events, along with elevated ozone levels and temperatures, to become more common. Our results suggest that ozone will be an important contributor to the adverse health effects of such events.     

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.     

Tick zoonoses in the southern part of Switzerland (Canton Ticino): occurrence of Borrelia burgdorferi sensu lato and Rickettsia sp.

The diversity and the distribution of tick species and their infection rates by the pathogenic micro-organism Borrelia burgdorferi sensu lato, the etiologic agent of Lyme borreliosis, and Rickettsia sp., were studied in Canton Ticino (the southern part of Switzerland). Ticks specimens collected from animals and humans were classified and analysed for the presence of both pathogens. In particular, PCR analysis was performed for the detection of Borrelia spirochetes in Ixodes ricinus and Ixodes hexagonus, and the hemolymph test was done on Rhipicephalus sanguineus for the detection of Rickettsia sp. PCR assays, performed on 424 of the 989 collected ticks, revealed a low rate of infection (around 2%) of both vectors I. ricinus and I. hexagonus by B. burgdorferi sensu lato. These results are in agreement with the modest number of Lyme borreliosis cases yearly recorded in Ticino. Further, through analysis of DNA sequences, the strains carried by the infected ticks were identified as belonging to the genomic group VS116. The widespread finding of the Mediterranean species Rhipicephalus sanguineus in different locations from July 1994 to October 1995 demonstrates its establishment in Ticino. Of the 210 specimens collected, 70 were analysed and one was infected by Rickettsia sp.     

Geographical differences on the mortality impact of heat waves in Europe

Climate change is potentially the biggest global health threat in the 21st century. Deaths related with heat waves and spread of infectious diseases will be part of the menace though the major impact will be caused by malnutrition, diarrhea and extreme climate events. Consequently, loss of healthy life years as a result of global climate change is predicted to be 500 times greater in poor African populations than in European populations. However, the increase of more than 2°C of average temperature will result in a negative health impact in all regions, the potential benefits of a warmer temperature being negatively compensated, heat waves being one of the largest climate change threats in the developed world.     

Major heat waves of 2003 and 2006 and health outcomes in Prague

We have investigated the association between heat waves and mortality and hospital admissions for Prague inhabitants for the summer heat waves of August 2003 and July 2006. The effect of heat waves was investigated using negative binomial regression in a generalized additive model. We used a linear model on a logarithmic scale, having 1-day lagged temperature differences from the long-term average, 1-day lagged ambient O₃ and PM₁₀ concentration, relative humidity, simple “heat wave” indicator, and smooth seasonal effect as explanatory variables. We found a small increase in daily mortality for the examined period. This increase can be attributed to PM₁₀ concentrations in most cases, and in fewer instances, to air temperature and O₃ concentrations. The “heat wave” indicator did not significantly increase the relative risk; the same held for the relative humidity. For the general unstratified population, the highest increase in relative risk of 1.072 (95% CI 1.001–1.147) was observed for cardiovascular mortality and was associated with an increase in temperature of 10 °C, followed by an increase in relative risk of 1.056 (95% CI 1.025–1.087) for respiratory mortality associated with an increase in O₃ concentrations by 10 μg.m^?3. A higher risk in most cases was found for women. A significant increase of relative risk of 1.013 (95 % CI 1.002–1.024) due to PM₁₀ was found for hospital admissions for cardiovascular causes. This issue should be studied further in view of the anticipated increase in meteorological extremes, including heat waves, in the future, to prepare prevention plans for eliminating their negative effects as far as possible.     

Сardiovascular mortality during heat waves in temperate climate: an association with bioclimatic indices

The authors studied the relative predictive powers of several bioclimatic indices as predictors of population mortality during heat waves. Daily mean and maximum values of air temperature, Humidex, apparent, and physiological equivalent temperatures (PETs) were examined. The numbers of daily deaths and daily meteorological data in Rostov-on-Don (southern Russia) were used. The study period spanned April–September between 1999 and 2011. The eight selected bioclimatic indices were used to identify heat waves and calculate the expected increases in mortality during such events from Poisson generalized linear model of daily death counts. All of the bioclimatic indices considered were positively and significantly associated with mortality during heat waves. The best predictor was chosen from a set of similar models by maximization of relative mortality risk estimates. Having compared the relative increases and their significance levels in several cause- and age-specific mortality rates, the authors concluded that PET was the most powerful predictor.     

The relation between temperature, ozone, and mortality in nine French cities during the heat wave of 2003

BACKGROUND: During August 2003, record high temperatures were observed across Europe, and France was the country most affected. During this period, elevated ozone concentrations were measured all over the country. Questions were raised concerning the contribution of O3 to the health impact of the summer 2003 heat wave. METHODS: We used a time-series design to analyze short-term effects of temperature and O3 pollution on mortality. Counts of deaths were regressed on temperatures and O3 levels, controlling for possible confounders: long-term trends, season, influenza outbreaks, day of the week, and bank holiday effects. For comparison with previous results of the nine cities, we calculated pooled excess risk using a random effect approach and an empirical Bayes approach. FINDINGS: For the nine cities, the excess risk of death is significant (1.01% ; 95% confidence interval, 0.58-1.44) for an increase of 10 microg/m3 in O3 level. For the 3-17 August 2003 period, the excess risk of deaths linked to O3 and temperatures together ranged from 10.6% in Le Havre to 174.7% in Paris. When we compared the relative contributions of O3 and temperature to this joint excess risk, the contribution of O3 varied according to the city, ranging from 2.5% in Bordeaux to 85.3% in Toulouse. INTERPRETATION: We observed heterogeneity among the nine cities not only for the joint effect of O3 and temperatures, but also for the relative contribution of each factor. These results confirmed that in urban areas O3 levels have a non-negligible impact in terms of public health.     

Contrasting patterns of mortality and hospital admissions during hot weather and heat waves in Greater London, UK

Background: Epidemiological research has shown that mortality increases during hot weather and heat waves, but little is known about the effect on non-fatal outcomes in the UK.

Aims and Methods: The effects of hot weather and heat waves on emergency hospital admissions were investigated in Greater London, UK, for a range of causes and age groups. Time series analyses were conducted of daily emergency hospital admissions, 1 April 1994 to 31 March 2000, using autoregressive Poisson models with adjustment for long term trend, season, day of week, public holidays, the Christmas period, influenza, relative humidity, air pollution (ozone, PM₁₀), and overdispersion. The effects of heat were modelled using the average of the daily mean temperature over the index and previous two days.

Results: There was no clear evidence of a relation between total emergency hospital admissions and high ambient temperatures, although there was evidence for heat related increases in emergency admissions for respiratory and renal disease, in children under 5, and for respiratory disease in the 75+ age group. During the heat wave of 29 July to 3 August 1995, hospital admissions showed a small non-significant increase: 2.6% (95% CI –2.2 to 7.6), while daily mortality rose by 10.8% (95% CI 2.8 to 19.3) after adjusting for time varying confounders.

Conclusions: The impact of hot weather on mortality is not paralleled by similar magnitude increases in hospital admissions in the UK, which supports the hypothesis that many heat related deaths occur in people before they come to medical attention. This has evident implications for public health, and merits further enquiry.

     

Impact of heat waves on daily mortality in distinct age groups

OBJECTIVES: To establish whether the daily maximum temperature during heat waves beyond which daily mortality increases differs in distinct age groups and to quantify the mortality increment by these age groups. METHODS: The dependent variable was daily mortality from all causes except for accidents in the city of Madrid from 1986 to 1997. The age groups analyzed were the following: 0-10 years, 18-44 years, 45-64 years, 65-74 years, and older than 75 years. Data on the daily maximum temperature in the summer months was used. Trend and seasonalities were adequately controlled for, as were air pollutant concentrations. Autoregressive moving average (ARIMA) and Poisson regression models were used. RESULTS: In all age groups except that aged less than 10 years old, there was an association between extremely high temperatures and mortality. Independently of age group, the temperature threshold above which mortality increased coincided with the 95th percentile of the maximum temperature data series for the summer months, which in Madrid is 36.5 degrees C. The daily mortality increment for each degree above this threshold was practically constant between the ages of 18 to 64 years but markedly increased in persons aged more than 65 years old. CONCLUSIONS: Mortality is associated with high temperatures in people younger than 64 years old and therefore prevention plans should not be focused exclusively on the elderly.