The age of the population is stressed as an important factor of vulnerability to heat wave: the youth and the elderly are most vulnerable to extreme heat and heat waves for physiological reasons (Kovats et al., 2006; Knowlton et al., 2009; Naughton et al., 2002; Poumadere et al., 2005; Reid et al., 2009; Auger et al., 2014) But there is a difference in the physiological reactions on heat stress.
The natural processes of ageing are associated with impairment of thermoregulation (Drinkwater and Horvath 1979). Moreover, in the elderly, high temperatures reduce the viscosity of the blood leading to increased risk of thrombosis. In most people over 65 which have impaired renal function and thermoregulation, the last can be influenced by cardiovascular disease, characteristics of the elderly. (Laaidi et al., 2012)
What is equally important is the period of exposure to heat of the elderly. Olivier Riou, MD, from the geriatrics department of Casanova hospital in Saint-Denis, during the interview on July 7, 2014 pointed out that the uncomfortably high temperatures during several days exhausts elderly people and might negatively influence their health condition. Exposure to high nighttime temperature over several days increases the probability of death during a heat wave, while the daytime temperature is less important (Besancenot, 2002)
Infants, children and adolescents are susceptible to heat stress because they have a greater surface area-to-body mass ratio than adults (AAP, 2000), which causes the heat gain from the environment on hot days greater than that of adults. In addition, during physical activity children produce more metabolic heat per mass unit than adults. The ability to sweat is significantly lower in children than in adults, which reduces their ability to dissipate body heat by evaporation (AAP 2000). Under conditions of high temperatures, infants and young children are exposed to dehydration which can be daunting. What should also be considered is that they can’t access appropriate fluid intake without external assistance and the youngest can even not communicate their thirst. All these specificities of youth make them more susceptible to heat stress.
Pregnant women are also more vulnerable to high ambient temperatures and extreme heat events: these conditions may trigger earlier delivery among term births (Auger et al., 2014)
According to the study conducted by the Institute for Health Monitoring the impact of the heat wave of summer 2003 in mortality was more pronounced in the elderly, especially those who are isolated, sick and have limited capacity to adapt to conditions of heat resources. Elderly people (over 75 years) were the main victims of a heat wave, or 82.5% of fatalities. (Laaidi et al., 2012; Poumadère et al., 2005). The excess mortality rate in Ile-de-France was high, especially in the departments of Essonne, Hauts-de-Seine, Seine-Saint-Denis et Val-de-Marne, where the excess mortality during the heat wave reached more than +150% (almost two times higher than in Ile-de-France) (Hémon, 2003)
Children are sensitive to discomfort due to hot weather. The impact of heat wave of summer 2003 in child in terms of morbidity was rather low and concerned primarily children 2 to 5 years. During the heat wave, the number of hospital visits for children under 2 years increased by only 7%, while the number of hospitalizations did not increase during this period, which can be explained by the vigilance of parents (Laaidi et al., 2012).
In 2003, people aged over 75 years accounted for 8.8% of the population of France, and due to population ageing this figure could rise to 15.6% in 2050 according to INSEE projections.
What concerns Plaine Commune in 2009 9.36% of its population was over 65, 10.5% – children under 6 years (INSEE 2010). Despite the fact that the population of Plaine Commune is rather young, it should not be overlooked that the elderly are more susceptible to high temperatures with more serious consequences, which is shown by the statistics of mortality during the 2003 heat wave.
To avoid the negative effects of high temperatures on the health and welfare of children and the elderly special accommodations (such as installation of air conditioners, air-conditioned room equipment, vegetation of areas around buildings, creating spaces of rest in shade, etc.) should be installed in homes, schools, leisure centers, in any institutions hosting vulnerable population.
The agents in the territory such as the services of visiting nurses care (SSIAD), support services and home support (SAAD), social services, customized to the medical and social teams allocation autonomy, community centers for Social Action (CCSA), local information and coordination centers (CLIC) gerontology, the county department of maternal and child health (MCH) must be informed and mobilized.
With regard to vulnerable people in their homes, especially the socially isolated and / or elderly patients, specific measures such as listing vulnerable persons should be provided. A database of vulnerable people must be maintained, the population informed of the risks.
In most cities of Plaine Commune municipal social welfare centers have implemented measures under the National Heatwave Plan (Plan Nationale Canicule), including registration of vulnerable people in the heatwave register. For example, the CCAS Villetaneuse set up a heat wave census. Elderly or any other vulnerable person can be registered online on the site Villetaneuse municipality. The list helps to identify the elderly or disabled who in an emergency might need medical or any other help.
A good example of how simple preventive steps taken by an institution significantly reduce the risk and impact of heat waves on the health of elderly people is the case of a nursing home in Cachan, Val-de-Marne. The nursing home hosts 135 permanent residents. Before the 2003 heat wave, the director of nursing home had undertaken a series of preventive measures ranging from dietary to medical procedures, including behavioral counseling for patients and staff (Association Monsieur Vincent, 2004). While the Department of Val-de-Marne had the highest level of excess mortality in France (+ 171%), the nursing home has lost only one patient during the heat wave, whose death was expected even before the heat wave (Poumadère et al, 2005).
National Heatwave Plan 2014 Sheet 4 “Young children” envisions installation (if possible) of air conditioners or equipment of a cool room duly equipped with blinds, refrigerator, and of course air conditioning system in care institutions before summer.