Geriatric Medicine and Gerontology
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ISSN: 2469-5858 Kaltsatou et al. J Geriatr Med Gerontol 2018, 4:053 DOI: 10.23937/2469-5858/1510053 Volume 4 | Issue 3 Journal of Open Access Geriatric Medicine and Gerontology REVIEW ARTICLE The Impact of Heat Waves on Mortality among the Elderly: A Mini Systematic Review Antonia Kaltsatou1, Glen P Kenny2,3 and Andreas D Flouris1,2* 1FAME Laboratory, Department of Exercise Science, University of Thessaly, Trikala, Greece 2Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Canada Check for updates 3Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ontario, Canada *Corresponding author: Andreas D. Flouris, FAME Laboratory, Department of Exercise Science, University of Thessaly, Karies, Trikala, 42100, Greece, Tel: +30-2431-500-601, Fax: +30-2431-047-042 of heat-vulnerable populations such as elderly adults. Abstract Such extremes have resulted in the deaths of 70,000 The aim of this systematic review was to review the recent in Europe in the summer 2003 [1] and 55,000 in Russia literature regarding the effect of heat waves on mortal- ity in elderly adults. A systematic search of the literature, during the summer 2010 heat wave [2]. The immense was conducted by two reviewers during March 2018, using burden placed on the health care systems worldwide as three electronic databases (PubMed, Web of Science, and a result of these heat waves has been unequivocal [3]. Scopus). The PRISMA guidelines were used for the quality When people are exposed to heat, especially when tem- assessment of the published studies. The literature search identified a total of 345 articles, while only 24 studies met the perature remains atypically high for several days such as inclusion criteria and were included in this analysis. Overall, occurs during the summer months, they can suffer from the results from these studies show that, although recent ad- potentially deadly illnesses such as heat exhaustion and vances in technology allow scientists to predict heat waves, heat stroke quickly [4]. Elderly with pre-existing health thereby enabling health agencies to alert the public with heat advisories, the number of heat wave-induced deaths conditions are particularly vulnerable as exposure to remains high. The underlying reasons for these increases even short periods of heat can aggravate their health in heat-wave-induced mortality remains unclear, highlighting conditions by worsening disease-specific symptoms [5]. the need for developing evidence-based thresholds for the Accordingly, a correlation between high ambient tem- activation and implementation of actions plans to protect the health of heat-vulnerable elderly populations. peratures and negative health outcomes exists. Epide- miological evidence demonstrates a 2-5% increase in Keywords all-cause mortality for a 1 °C increase in average daily Extreme heat events, Older, Aging, Deaths, Heat stress, temperature during hot temperature periods [6]. How- Heat shock, Hyperthermia ever, extreme heat events occurring in spring or early summer pose an even greater threat to health in the Introduction elderly because of their lack of acclimation [7]. Extreme heat conditions are considered a major A heat wave is usually considered a prolonged peri- threat for public health and can induce many health od of excessive heat. According to Gasprarrini and Ar- complications to the urban populations. With a predict- mostrong [8] a heat wave is defined as a period where ed rise in the frequency and intensity of extremely hot for ≥ 2 repeated days the daily mean temperature is at weather due to changing climate, heat exposure is pre- or above the 98th percentile of the warm season daily senting an increasing challenge to the health and safety mean temperature. Moreover, the intensity, the dura- Citation: Kaltsatou A, Kenny GP, Flouris AD (2018) The Impact of Heat Waves on Mortality among the Elderly: A Mini Systematic Review. J Geriatr Med Gerontol 4:053. doi.org/10.23937/2469- 5858/1510053 Accepted: September 27, 2018: Published: September 29, 2018 Copyright: © 2018 Kaltsatou A, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Kaltsatou et al. J Geriatr Med Gerontol 2018, 4:053 • Page 1 of 9 • DOI: 10.23937/2469-5858/1510053 ISSN: 2469-5858 tion and the time in the season that it appears, are the temperature than their younger counterparts [20]. This main characteristics of each heat wave [8]. Moreover, response is due to age-related reductions in heat loss as the rapidly aging population relocates to large urban responses of sweating [21,22] and skin vasodilation [23- centres to be closer to essential health and social care 27], which are paralleled by marked impairments in the services, they are likely to experience some of the high- whole-body heat dissipation [18], and occur independ- est temperatures during hot weather periods. This is ently of the individual’s level of acclimation [23]. As a because of the urban heat island where temperatures consequence, elderly people are less heat tolerant and within major metropolitan cities (e.g., London, England; are at an increased risk of heat-related morbidity and Toronto, Canada, New York City, USA; Paris, France) can mortality [17,28]. be as much as 10 °C greater than the surrounding rural Given the fact that the population over age 65 years areas [9-11]. These elevated temperature are primarily is steadily increasing [29] the numbers of heat relat- due to the design and density of buildings and by oth- ed illnesses and deaths are likely to rise exponentially. er manmade changes which includes asphalt roads and Accordingly, there has been an increased urgency to pathways, removal of trees, elimination of open green address this important public health issue. This is evi- space areas, others [12]. denced by the fact that the number of articles (total of Elderly persons are typically considered those who 507 based on search term “heat wave mortality” and are aged 65 years or more [13]. Natural ageing can be “elderly”) published in PubMed are appearing with in- characterized by a complex process, in which progres- creased frequency (~16 articles per year) over the past sive age-specific deteriorations of internal physiologic- five years (Figure 1). Experts suggest that appropriate al systems inevitably impair the body’s capacity to re- health prevention and management programs could spond appropriately to internal and external stressors greatly limit heat-related morbidity and mortality in [14-16]. As recent studies show, this includes deterior- heat vulnerable populations such as the elderly [30,31]. ation in their ability to dissipate heat [17-19], a process To contribute towards addressing these concerns, the pivotal in the maintenance of normal core temperature aim of this systematic review was to review the recent especially in extreme heat conditions. Specifically, older literature regarding the effect of heat waves on mortal- adults take longer to respond to increases in ambient air ity in elderly adults. 18 16 14 12 10 8 6 Publication per year Publication per 4 2 0 1968 1973 1978 1983 1988 1993 1998 2003 2008 2013 2018 Time Figure 1: Evolution of Publications that revealed using the keywords of “heat wave mortality” and “elderly” clearly showing a growing interest in this field. A total of 223 articles appeared with increasing frequency through time reaching a peak of 16 articles/year during the past seventeen years. Kaltsatou et al. J Geriatr Med Gerontol 2018, 4:053 • Page 2 of 9 • DOI: 10.23937/2469-5858/1510053 ISSN: 2469-5858 Methods only the relative risk for mortality or models for the dai- ly mortality prediction; 2) Did not evaluate the elderly Literature search and identification mortality but mortality rates in other age groups and The current review included epidemiological stud- 3) Were studies published only in abstract form. Stud- ies that report on epidemiological data regarding the ies identified in the search were initially examined us- effect of heat waves on elderly mortality. A systemat- ing the information presented in the title and abstract. ic search of literature was conducted by two reviewers Thereafter a full evaluation of the full-text copy of the during March 2018 using three electronic databases article was conducted to determine if it met all inclusion (PubMed, Web of Science and Scopus). The PRISMA criteria. guidelines were used for the quality assessment of the Results published studies [32]. Studies were selected using in- clusion and exclusion criteria. Studies were included in A total of 345 articles were identified in the search. the study if: 1) Results for elderly mortality rates during Of these, 85 full-text articles were reviewed for eligibil- heat waves were presented; 2) Results for the effect of ity and only 24 studies met the inclusion criteria (Figure “heat waves” on “elderly mortality” as a sub-population 2). Articles were excluded for the following reasons: 12 were reported; and 3) The study was written in English. referred to animal, pregnancy, and infant mortality dur- Studies were excluded when they: 1) Did not present ing heat waves; 22 examined the impact of heat waves the number of deaths during “heat wave” periods but mortality on specific chronic diseases; 5 studies were re- n o Records identified through Additional records identified ti a c database searching through other sources fi ti (n = 483) (n = 138) n e d I Records after duplicates removed (n = 345) g n i n e e r c S Records screened Records excluded (n = 345) (n = 265) Full-text articles assessed Full-text articles excluded, y t for eligibility with reasons i l i b (n = 85) (n = 61) i g i l ) E Studies included in d quantitative synthesis e d (n = 24) u l c n I Figure 2: Flowchart of the progress of the literature screening.