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The Mediterranean region under climate change

 | 
Jean-Paul Moatti
, 
Stéphane Thiébault

Part 2. Vulnerability and impacts

Sub-chapter 2.5.2. The impacts of climate change on non-communicable diseases in the Mediterranean region

Isabella Annesi-Maesano

Texte intégral

1According to the existing literature (Suk and Semenza 2011), climate change will increase the incidence of non-communicable diseases (NCDs), including cardiovascular disease (CVD), respiratory diseases, some cancers, mental disorders, injuries, and malnutrition and overall poor health among all populations through direct and indirect effects (see Table 1).

2A number of studies have shown that the elderly, children, people with pre-existing chronic conditions (i.e. respiratory diseases, CVD, diabetes) and individuals with a low socio-economic status, are at higher risk of suffering from climate change effects.

Extreme weather and related events have direct health effects in the Mediterranean region

3The frequency of extreme natural hazards and weather events including heat waves, cold spells, floods, storms and droughts has been increasing in recent decades in Europe and specifically in the Mediterranean region due to climate change. Among them, the key climatic change factors that directly influence NCDs are extreme temperature events, barometric pressure, floods and storms (see Table 1).

4Since the 1960s, the Mediterranean region has become warmer with a significant increase in the frequency, intensity and duration of heat waves (Kuglitsch et al. 2010) and of related health effects. In the ‘Assessment and Prevention of Acute Health Effects of Weather Conditions in Europe (PHEWE)’ project, including Mediterranean cities, high temperatures had a specific impact on respiratory admissions, particularly in the elderly population (Michelozzi et al. 2009). This is because, among elderly, the body temperature increases with the mean outdoor temperature. Heat effects are also observed in children (Iñiguez et al. 2016), for whom hospitalization for natural causes rose significantly with heat in Rome and Valencia between 2001 and 2010. Patterns of delays and critical windows of exposure varied according to the outcome considered with respiratory and gastrointestinal diseases being the leading causes for short and long-term lags respectively. Less expected are the effects of cold spells that belongs to the kind of extreme events whose frequency is increasing due to climate changes. In adults, winter deaths are due to influenza, coronary thrombosis and respiratory diseases. Coronary thrombosis deaths peak about two days after the peak of a cold spell whereas respiratory disease, namely pneumonia and COPD exacerbations, peak about 12 days after the peak cold. The rapid coronary deaths are due mainly to haemoconcentration resulting from fluid shifts during cold exposure; some later coronary deaths are secondary to respiratory disease. In Italy, excess deaths among the elderly were recorded in the 14 cities that suffered from a cold spell in February 2012 (de Donato et al. 2013). Cause-specific analysis showed a statistically significant excess in mortality for respiratory disease, COPD, cardiovascular disease, ischemic heart disease. Similar results were reported for emergency room visits. In the PHEWE project mentioned above (Michelozzi et al. 2009), a decrease in temperature was associated with an increase in the daily number of total natural deaths and specifically with an increase in cardiovascular, respiratory, and cerebrovascular deaths, respectively. The increase was greater among older age groups. The cold effect was found to be greater in warmer (southern) cities and persisted up to 23 days, with no evidence of mortality displacement (Analitis et al. 2008). A recent study in the Czech Republic investigated differences in the effects on acute and chronic diseases following extreme cold and hot temperature (Davídkovová et al. 2014). While excess deaths due to ischemic heart disease (IHD) during hot spells were mainly of persons with chronic diseases whose health had already been compromised, cardiovascular changes induced by cold stress may result in deaths from acute coronary events rather than chronic IHD, and this effect was also important in the younger population. This suggests that the most vulnerable population groups as well as the most affected cardiovascular diseases differ between hot and cold spells, which needs to be taken into account when designing and implementing preventive actions.

Table 1. Direct and indirect effects of climate change on non-communicable diseases (NCDs).

Climate change effects

Additional factors contributing to the indirect effect

NCD

Direction of the risk

Direct:

Indirect:

Heat extreme

CDV and respiratory morbidity and mortality

Increase

Cold extremes

Cardiorespiratory morbidity and mortality

Increase

Low atmospheric pressure during storms

ISP

Increase

Extreme weather events (floods, storms, etc.)

Injury, Impaired mental health, Impoverishment

Increase

Storms

Pollen breaking

Asthma

Drought

Malnutrition, Impaired mental health

Increase

Pests

Increasing use of pesticides

Asthma, Parkinson’s disease, Cancers

Increase

Aflatoxin (fungal metabolite)

Cereal contamination

Liver cancer

Increase

Increased temperature, windless conditions

Higher groundlevel ozone

Urbanization

Increased respiratory tract irritation, CDV and chronic pulmonary disease hospitalizations, and lung disease mortality

Increase

Wildfires, drought

Higher Particular Matter level

Urbanization

COPD exacerbations, Mental illness

Increase

Altered trajectory of recovery of stratospheric ozone with changes in precipitation and cloud coverage

Altered ambient ultraviolet radiation (UVR)

Skin cancer
Autoimmune diseases (multiple sclerosis)

Increase
Decrease

Global warming

Higher pollen counts and allergenicity

Longer pollen season, modified pollen distribution

Allergic rhinitis (hay fever) and asthma

Increase

Floods

More molds

Allergic rhinitis, sinusitis and asthma, hypersensitivity pneumonitis, mycotoxin toxicity

Increase

*: in temperate zones including Mediterranean zones
ISP: Idiopathic spontaneous pneumothorax

5The frequency of heavy precipitation and flooding events is likely to increase or to become more intense as a result of climate change in the Mediterranean region (see corresponding section). In the past decades, in Europe and specifically in the Mediterranean areas, they caused damage to properties, personal injuries, enteric infections, increase in mental health problems (anxiety, depression, sleeplessness, deaths or post-traumatic stress syndrome), and potential contamination by toxic chemicals in exposed and vulnerable people (Messeri et al. 2015). Unexpectedly, although the risk of death most obviously increased during the period of flooding, a controlled study of the 1969 floods in Bristol, United Kingdom, reported a 50% increase in all-cause deaths in the flooded population in the year following the flood, most pronounced among those aged 45-64 years.

6In addition there is an increasing body of evidence for the occurrence of severe asthma epidemics during thunderstorms in various geographical zones including in the Mediterranean region (D’Amato et al. 2016). The main hypotheses explaining association between thunderstorms and asthma claim that thunderstorms can concentrate pollen grains and molds spores at ground level due to atmospheric pressure, which may then release allergenic particles of respirable size in the atmosphere after their rupture by osmotic shock. The pressure has been involved also in idiopathic spontaneous pneumothorax (ISP). Variations in the atmospheric pressure have been involved in the initiating mechanisms (rupture of lung blebs, bullas or damaged alveolar walls) of ISP due to increased trans-pulmonary pressure during storms (Alifano et al. 2007).

Chemical and biological air pollutants have indirect effects on health in the Mediterranean region

7Climate change also increases the likelihood for individuals to be exposed to chemical air pollutants and bio-contaminants like viruses, bacteria, pollens and molds, which are established causes of NCD incidence or exacerbation (Table 1) (Ziska and Beggs 2012).

8Climate change can affect air quality and vice versa air quality can impact climate change because many air pollutants are greenhouse gases due to human activities and natural phenomena (Ayres et al. 2009). Extra sunlight and higher temperatures due to global warming will lead to longer episodes of ozone peaks, generally in large cities. Higher concentrations of gases and particles are expected due to increased human activity and traffic in large cities where in the long run, a large majority of the world population will be forced to live as a result of climate change related factors, sea level rise among others. Air pollution has been linked to a broad spectrum of NCDs (diabetes, cardiopulmonary diseases, neurodegenerative diseases, etc.). High levels of vehicle emissions and westernized lifestyle have been correlated with increased aggravation of NCDs (Baldacci et al. 2015). Important data for the Mediterranean area result from ad hoc case studies (Baldacci et al. 2015). Among them, the European MED-PARTICLES project, which followed up climate, air pollution and health in 10 European Mediterranean metropolitan areas from 2001 to 2010. MED-PARTICLES findings provide support for short-term effects of PM2.5 on mortality due to diabetes, cardiac causes, COPD, and to a lesser extent to cerebrovascular causes, in the European Mediterranean region (Samoli et al. 2014). Several PM constituents originating from different sources, were involved in the relationships between PM and hospital admissions in the Mediterranean area (Basagaña et al. 2015). In particular, black carbon (BC), which in western industrialized nations derives primarily from diesel engines and biomass burning, is a significant public health burden, particularly in European cities with high traffic density (Ostro et al. 2015). In addition, epidemiological and toxicological research suggests a causative relationship between air pollution and the increased incidence of NCDs although no specific data are available for the Mediterranean region due to the absence of longitudinal studies (Ahn 2014, Baldacci et al. 2015). This is why air pollution is considered to be one of the factors that may explain the increase in allergic and respiratory diseases and their worsening over recent decades.

9In addition to anthropogenic air pollution, natural air pollution also constitutes a real danger for the people living within Mediterranean area. The concentration of particles will increase because of desertification and wildfires (D’Amato et al. 2015).

10The number of wildfires has increased dramatically in Europe (Youssouf et al. 2014). In the Mediterranean area, forest fires usually occur during spring and summer, they overlap with Saharan outbreaks, are associated with increased temperature and their health effects are mostly due to an increase in particulate matter. Based on the literature, various studies have established the relationship between PM10 and PM2.5 and cardiorespiratory symptoms in terms of emergency room visits and hospital admissions (Youssouf et al. 2014). Associations between wildfire emissions and various subclinical effects have also been established. However, few relationships between wildfire emissions and mortality have been observed (Youssouf et al. 2014). Certain segments of the population may be particularly vulnerable to smoke-related health risks. Among them, people with pre-existing cardiopulmonary conditions, the elderly, smokers and, for professional reasons, firefighters. Surveillance of wildfires and PM10 in 10 southern European cities in Spain, France, Italy and Greece (2003-2010) using satellite data showed that smoke was associated with increased cardiovascular mortality in urban residents, and PM10 on smoky days has a larger effect on cardiovascular and respiratory mortality than on other days (Faustini et al. 2105).

11In addition, outbreaks of Sahelo-Saharan dust over Mediterranean areas are frequent and often exceed the European Union’s 24-hr standard of 50 µg/m3 for PM10. Evidence for the effects of coarse particles (PM2.5-10 and PM10) on natural and cause-specific mortality, with stronger estimated effects on cardiac mortality has been collected during dust outbreaks in Rome (Mallone et al. 2011). Identification of PM10 originating from the desert through satellite images confirmed a positive association with mortality and hospitalizations in Southern Europe. Recent experimental work confirmed that the redox activity of particles is amplified by ozone, raising the possibility of a three-way interaction between particles, ozone and temperature in the future. The situation is particularly alarming in the Mediterranean area as shown by peaks of ozone and desert storms.

12Excessive exposure of the skin to the sun causes skin cancer (Lucas et al. 2015). Solar irradiation also induces systemic immune suppression that may have adverse effects on health, such as through the reactivation of latent viral infections, but even beneficial effects through suppression of autoimmune reactivity. UV-B irradiation of the skin is the main source of vitamin D that plays a critical role in the maintenance of calcium homeostasis in the body in many geographic locations (Lucas et al. 2015). These dual results make it difficult to provide public health messages to guide safe exposure to the sun except that excessive exposure should be avoided.

13Floods following extreme weather events and related humidity can lead to mold allergies and the development of asthma in susceptible individuals (D’Amato et al. 2015).

14Lastly, climate is at the origin of a change in the geographic distribution of some plants, earlier onset and extension of the pollen season, and increased production of pollen and pollen allergens by the same plant due to the effect of the temperature (D’Amato et al. 2007). New plants can also arrive. Recent trends to warmer summers and increased volumes of international trade have accelerated the ragweed invasion notably. All these phenomena greatly increase the risk of allergic sensitization and of the development of asthma and allergic rhinitis.

15Since airborne allergens and air pollutants frequently increase simultaneously in the atmosphere, enhanced IgE-mediated response to aeroallergens and enhanced airway inflammation could account for the increasing frequency of respiratory allergy and asthma in atopic subjects in the last five decades. Observation data show that exposure of pollens to high concentrations of air pollutants significantly increases their fragility and disruption, leading to subsequent release of pollen cytoplasmic granules into the atmosphere (D’Amato et al. 2015), which could increase the incidence of allergic airway disease in sensitized individuals by facilitating the bioavailability of airborne pollen allergens. Experimental data highlight a direct influence of elevated NO2 on the increased allergenicity of ragweed pollen (Zhao et al. 2016). Climatic factors (temperature, wind speed, humidity, thunderstorms, etc.) can affect both components (biological and chemical) of this interaction.

Non-communicable disease concerns in the future

16In Europe, an increase in the frequency and intensity of summer heatwaves is expected, especially in central, eastern and southern countries (McMichael et al. 2006). These changes will increase the burden of diseases and of premature deaths, particularly in population subgroups with limited adaptive capacity, such as the elderly and patients with COPD, but statistics on populations in different climates suggest that, given time, people will adjust to global warming with little change in either mortality. In contrast, global warming can be expected to reduce flu related deaths, especially in the case of people suffering from pre-existing NCDs. The number of extreme meteorological events will also increase. Pollens and molds will rise and engender allergic morbidity. Molds can also be at origin of other morbidities. Current indications are that air pollution will remain the main environmental cause of illness and death in the Mediterranean region, but these events are hard to differentiate from the morbidity and mortality due to the weather and other factors, and clear identification of air pollution deaths and diseases may need more extensive data than is currently available in the Mediterranean.

© IRD Éditions, 2016

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