I. Overview of the Working Paper

The threat of global climate change has the potential to cause large-scale drought, increased incidence of disease, shortages of water and food, rising sea levels, and increased extreme weather events (IPCC (b), 2007). If atmospheric concentrations of greenhouse gasses remain unabated, scientists predict that widespread ecosystem collapse will ensue. These stressors to human habitability will be borne disproportionately by the most vulnerable of human populations.

Older populations are among the most at risk due to decreased mobility, changes in physiology, and more limited access to resources, all of which may limit adaptive capacity among older and more vulnerable people. Older, vulnerable populations will face adaptive challenges to their new environments, with potentially far-reaching implications for health as well as for societal strategies to cope with climate change effects at both the population and policy level.

Thus, climate change presents major challenges regarding the well-being of older populations. Habitability, health, and justice will be challenged as the adverse effects of climate change interact with vulnerable older populations. It is critical to develop a research agenda on climate change vulnerability in old age, including the types of exposure factors that may exist, heightened vulnerability among older people to specific exposure factors, analysis of how exposure and susceptibility are distributed in the older population, and ultimately what actions can be taken to reduce vulnerability.

This working paper aims to provide a brief overview of the subject and identifies areas for a research agenda on the topic. The paper touches on several major themes, including a brief review of the scientific consensus on the impact of climate change on the environment; known health risks to older persons from environmental threats; and how the sequelae of climate change may affect older people’s health over the coming decades.

II. Overview of Climate Change

The earth’s global mean climate is determined by incoming energy from the sun and by the properties (reflection, absorption, and emission of energy) of the earth and its atmosphere. Changes in the earth’s global climate result from factors such as the dynamic processes of the earth (volcanoes, plate tectonics), external forces (solar radiation, orbital properties), and more recently human activities (emission of greenhouse gases, land use).

Our knowledge of the earth’s past climate changes is recorded in ice cores—drilled to more than 3,600 meters (slightly more than 2.2 miles deep) and representing 650,000 years’ accumulation. In June 1999, the latest ice core data from the Vostok site in Antarctica were published by Petit et al (Figure 1), revealing a linear relationship between atmospheric carbon dioxide concentration and global mean temperature.

Figure 1. Atmospheric temperatures based on ice core drillings from Vostok.

Petit, J.R., et al. 1999. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399: 429-436

Presently, anthropogenic carbon emissions are approximately 25 billion tons (gigatons-GT) of carbon dioxide (CO₂) annually. The global atmospheric concentration of CO₂ has increased from around 280 ppm in the pre-industrial era to 379 ppm in 2005 (IPCC (a), 2007). The atmospheric concentration of CO₂ in 2005 exceeds the natural range over the last 650,000 years (180 to 300 ppm), as determined from ice cores (IPCC (a), 2007).

The Intergovernmental Panel on Climate Change (IPCC), a scientific body tasked to evaluate the risks of climate change and publish reports relevant to the implementation of The United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol, has prepared their fourth assessment on the scientific, technical, and socio-economic information relevant for the understanding of the risk of human-induced climate change. Their findings indicate that fossil fuel use, agriculture, and land use have been the dominant cause of the increase in greenhouse gases emitted to the atmosphere over the last 250 years. Global mean surface temperatures have continued to rise. Eleven of the last twelve years rank among the twelve warmest years on record since 1850. Droughts have become more common, especially in the tropics and subtropics, since the 1970s. Furthermore, since 1961 global average sea level has risen at a mean rate of 1.8 mm/yr and even higher since 1993 at 3.1 mm/yr, with contributions from thermal expansion, melting glaciers and ice caps, and the degeneration of the polar ice sheets.

If we accept that levels of CO₂ in excess of 400 ppm in the atmosphere pose a threat to our environment, then the dual challenges that face us are i) to remove CO₂ from the atmosphere and stabilize it against re-release, and ii) to reduce the rate of release of CO₂ to the atmosphere. Many of these findings indicate that unabated global warming will have serious impacts on the environment, food production, political stability, and human health.

III. Heightened Vulnerability to Environmental Health Risks for Older Persons

Public health research suggests that there are a number of environmental threats that disproportionately compromise the health of the older population. Several recent reports suggest that older persons will be at increased risk due to global climate change. They are more vulnerable to the effects of temperature extremes and have a significantly higher mortality risk in extreme weather events, both of which are likely to be affected by climate change. The changing climate has the potential to increase the risk for extreme weather events, exacerbate vector- borne diseases, compromise agriculture, reduce the availability of fresh water, and decrease habitability of human population centers. The older population is at greater risk for adverse health effects from increased heating and cooling, susceptibility to disease, stresses on the food and water supply, and reduced ability to mobilize quickly.

Table 1 provides a summary of some possible threats as well as potential health impacts and mitigating factors.

Table 1. Possible Health Threats to Older Adults from Climate Change¹

1. Sources: Haq et al., 2008; Table 1, p. 13; Geller & Zenick, 2005, Figure 1, p. 1258; McGeehin & Mirabelli, 2001, Figure 1, p. 186.

IV. Specific Health Risks Likely to Result from Climate Change

The health effects of climate change on older people can be classified into two categories: (1) those due to the greater exposure of older people to the threat (the dose) and (2) those that are a combination of exposure plus greater reactivity as a characteristic of aging (increased physiological susceptibility) or social factors that vary across people (social susceptibility).

Overall, the research literature suggests that greater reactivity (increasing physiological and social susceptibility) may best account for many of the negative health effects of climate change on older people. The effects of exposure to threats associated with climate change are variable in respect to the pre-exposure health of older people, depending on health status, psychological, and social characteristics (Geller and Zenick, 2001, Figure 1). Indeed, turning age 65 does not in itself make a person more vulnerable; rather, more proximate physiological and social factors that are associated with aging may produce greater vulnerability to the negative impacts of climate change.

For example, the oldest old (age 85 and over) are more likely to suffer negative health effects (Haq, Whitelegg, & Kohler, 2008), although chronological age is only an approximation of the true underlying condition of risk, physical decline, or frailty (McGeehin & Mirabelli, 2001). Those individuals who suffer from multiple pre-existing chronic conditions and those who take medications that exacerbate the impact of exposure to heat, pollutants, and vector-borne diseases are also more vulnerable (Geller & Zenick, 2001). Lack of physical mobility is also a proximate risk factor (Haq et al., 2008).

Social and economic factors will also increase the vulnerability of some older people who are exposed to the negative impacts of climate change. Socioeconomic disadvantages restrict the capacity of individuals to avoid the negative health impacts of climate change, mitigate those impacts, or cope with them if they cannot be mitigated or avoided. Those who are poorer, less educated, less connected to transportation, and less geographically mobile will be at risk of for negative outcomes in natural disasters (Haq et al., 2008). In addition to the previously mentioned socioeconomic factors—sometimes termed social exclusion (Wilkinson & Marmot, 2003)—social isolation, small or restricted social networks, and fewer connections with the larger community also are associated with morbidity and mortality. The combination of chronic health problems and social isolation may also be particularly problematic (Haq et al., 2008). To the extent that such factors are disproportionately concentrated among older persons, they may be at greater risk.

We have thus far emphasized characteristics that are more likely to be present among older people. However, other pathways creating reactivity to climate change threats are likely due not only to the aging process but also through accumulated exposures over the life course. There is suggestive evidence that reactivity to the negative health effects of climate change can be programmed in the body by early exposures to neurotoxins and air pollution (Cohn & MacPhail, 1996; Stein, Schettler, Rohrer, & Valenti, 2008). It has been well established that early life exposures are associated with a greater probability of developing cardiovascular disease and related conditions. Similarly, early exposure to pesticides and other neurotoxins may be associated with a greater probability of neurodegeneration later in life (Stein et al., 2008). The proximate pathway is that environmental toxins and air pollutants produce a heightened inflammatory response; in turn, excess inflammation is associated with cardiovascular disease, diabetes, and conditions such as Alzheimer’s. Exposure to neurotoxins and pollution is greater among those of lower socioeconomic status (e.g. Filleul, Rondeau, Cantagrel, Dartigues, & Tessier, 2004). Built up over decades, the accumulated exposure can produce greater sensitivity to health threats in later life (Stein, Schettler et al., 2008).

Table 2 summarizes some of the functional changes that may result from aging.

Table 2. Functional Changes Due to Aging and Increasing Frailty in Older Adults That May Increase Susceptibility to Climate Change Threats²

2. Sources: Geller & Zenick, 2005, Table 1, p. 1259; Stein et al., 2008

In the following sections, we focus on several specific ways in which effects of climate change may produce risk for older people. This list is of course not definitive, but provides examples of the range of potential problems.

IV.1 Heat waves and health risks to older people

Studies of the health impacts of extreme heat waves on older people are rich sources of information about the potential impacts of climate change. The studies illuminate the role of both physiological and social factors in susceptibility as well as community- and individual-level mitigation strategies. The evidence suggests that understanding the proximate factors that increase susceptibility of older people would lead to more effective interventions.

There is evidence that the impacts of exposure to heat are variable in the U.S. depending on how well housing structures and communities have accommodated to hot climate conditions over time. For example, McGeehin and Mirabelli (2001), analyzing epidemiological data on heat-related morbidity and mortality, observed that heat-related health events are more likely to occur in the U.S. where extreme heat is not usual and expected (for a similar observation in Europe, see Diaz et al., 2002a). An analysis of the health outcomes of the 2006 California heat wave (Knowlton et al., 2009) found that “population acclimatization and adaptive capacity influenced risk” (p. 61) and confirmed that older people and young children were the most likely to suffer health problems. This suggests that community and individual adaptation (e.g. air conditioning, use of community cooling centers, air filtration to reduce exposure to air pollutants) can be effective mitigation strategies during severe heat waves.

Individual physiological factors also interact with exposure to heat. Underlying chronic medical conditions (e.g. cardiovascular disease, obesity) exacerbate susceptibility (McGeehin & Mirabelli, 2001; Diaz et al., 2002b), as do medications that affect the body’s capacity to adapt to temperature changes (Bouchama, 2004). Thus effective interventions to reduce the health impacts of heat should also involve targeting those who have multiple risks because of pre-existing health conditions.

Social isolation and limited income are also proximate factors that increase susceptibility to heat-related illness among older people. Klinenberg’s Heat Wave (2002) documented the toll of the 1995 Chicago heat wave on socially isolated, physically impaired older Chicagoans. In reference to the 2003 European heat wave, Bouchama (2004) described the lethal combination of social isolation with psychiatric, pulmonary, and cardiovascular co-morbidities among older victims. Knowlton et al. (2009) argued that the combination of low socioeconomic status and social isolation led to a failure of “adaptive capacity” (p. 61) in some areas of central California during the 2006 Southwestern heat wave.

In sum, research on the effect of heat waves on older people suggests that interventions to mitigate the impact of changing climate on older people should target older adults with multiple risk factors (health conditions, small social networks, lower socioeconomic status). Kovats and Ebi (2006) go so far as to state that education and outreach to all older people about the dangers of heat may be relatively ineffective in reducing morbidity and mortality. On the other hand, they also point out that European experience demonstrates that older people with more risk factors for heat-related illness are less likely to use community centers or to be able to take protective action on their own because of health co-morbidities that reduce their adaptive capacity. Reluctance to use community resources generalizes to the U.S.; Klinenberg (2002) found that many older adults did not take advantage of community cooling centers because of fear of crime.

IV.2 Hurricane disasters and older people

Climate change is likely to be associated with the occurrence of more frequent and severe storms, most particularly hurricanes. Studies of Hurricane Andrew (1992), the six Florida hurricanes in 2004, and Hurricane Katrina (2005) have contributed new information about how exposure to climate change may disproportionately affect older people. As with research on heat waves, however, research on hurricanes suggests that the effect will be more severe among older people who have reduced or declining adaptive capacity, including the disabled, the poor, and the socially isolated.

An analysis of county-level census and spatial hazards data in the U.S. shows that older people are more likely to be exposed to natural hazards (Zimmerman et al., 2007). About 20 percent of older people reside in a county where a hurricane or large tropical storm is likely to make landfall over a ten-year period. These data also suggest that there is a higher concentration of low-income older people in the vulnerable counties (a situation that may worsen in the future as those with means relocate further away from vulnerable areas). Because of the concentration of older people in these counties, there are also a number of long-term care facilities, a special cause for concern when evacuation is ordered (Hyer et al., 2006).

Older people are also disproportionately more likely to die as a result of hurricanes. This tendency was evident in the case of Hurricane Andrew; while flooding did not occur, older people were more likely to die of indirect causes, such as heart attacks during evacuation (Combs et al., 1996). When flooding does occur, as in the case of Hurricane Katrina, those with physical impairments and who lack social contacts to assist them or who lack personal transportation are much more likely to be victims because of the inability to flee (Sherman & Shapiro, 2005; Fernandez et al., 2002). Seventy-four percent of the deaths related to Hurricane Katrina were among those age 60 and over, and 50 percent of these deaths were people over age 75 (Hyer et al., 2006).

Older people may also be less responsive to hurricane warnings, have minor physical impairments (such as mild arthritis) that make preparation more difficult, suffer from major impairments that make evacuation impossible, and be less connected to community assistance resources (Donner & Rodriguez, 2008). Despite a sophisticated warning system in Florida, during the 2004 hurricane season when six hurricanes made landfall in the state, older people were no more likely to evacuate than younger people (Smith & McCarty, 2007). The latter finding, based on a sample survey of the most affected areas in Florida, implies that older people do not consider themselves to be at special risk, or perhaps that evacuating is perceived as too large a burden relative to the worry of leaving property untended and seeking shelter away from home.

Similar to heat waves, the research on the health impacts of hurricanes on older people suggests that “one-size-fits-all” approaches may not be the most effective approach (Cutter & Emrich, 2006, p. 102). Indeed, more targeted approaches to evacuating frail and vulnerable older people have already been developed. For example, the Hartford Foundation supported a “hurricane summit” to develop strategies for evacuating frail older people (Hyer et al., 2006).

Cutter and Emrich (2006) have developed an index of social vulnerability, based on county-level indicators of social, economic, and physical vulnerability that can be used to target areas for special natural disaster planning in the U.S. The index incorporates forty-two county-level socioeconomic, demographic, and environmental variables, including built environment, that measure hazard potential and geographic, biophysical, and social vulnerability (Cutter, Boruff, & Shirley, 2003).

Differential vulnerability, as defined by this index, was associated with the relative ability of directly affected U.S. counties to respond to and recover from Hurricane Katrina (Cutter & Emrich, 2006). Of the multiple factors encompassed by this index, socioeconomic status indicators explained the most internal variance; these factors in Katrina-affected counties included employment disparities by race and gender, age structure, debt/revenue ratio, infrastructure employment, and lack of alternative employment sectors to agriculture. The social vulnerability index was also associated with the level of pre-existing coastal erosion in the counties affected by Katrina, suggesting that there are social as well as physical factors that contribute to vulnerability to coastal erosion (Cutter & Emrich, 2006).

IV.3. Air pollution and older people

Studies of the health effects of air pollution have also focused on susceptibilities to pollution that occur more frequently among older people, particularly medical co-morbidities. Bateson and Schwartz (2004) found heightened risk of death in the Chicago area from high levels of particulate matter (PM) among people with any type of heart or lung disease, and also among older people with a history of myocardial infarction or diabetes. Similar patterns of susceptibility have also been reported for older people exposed to black smoke (Filleul et al., 2004). The influence of social factors has been tested in other studies. Martins and colleagues (2003) found that socioeconomic deprivation increased the rate of PM-related mortality in Sào Paulo, Brazil; however, Bateson and Schwartz (2004) did not establish such an effect in the Chicago area. Filleul and colleagues (2004) reported that deaths attributable to black smoke were more likely among those who lived alone.

V. Special Issue – Climate Justice and Equity

The basic sense of the term “vulnerability” is that one is susceptible to damage or harm (Liverman, 1994) or that the capacity of individuals and social groups to respond and adapt to an external stressor is challenged (Kelly and Adger, 2000). Climate change and its effects increase vulnerability in this sense. However, the impact may be greater on certain sub-populations. Specifically, climate change will almost certainly exact the heaviest toll among those most socioeconomically disadvantaged, the poor, the very young, and the old (IPCC, 2007 (b), Paavola and Adger, 2006), who are in turn more vulnerable due to lack of financial resources, dependence on subsistence agriculture, and institutional impoverishment (Richards, 2003). The effect of climate change on the sources of health for older populations—notably access to food, water, housing, and social support—exhibit similar differential impacts. The extreme weather event of excessive heat in 1995 killed a disproportionate number of older African Americans in Chicago (Klinenberg, 2002), while a 2003 heat wave in Europe led to approximately 35,000 deaths, most among the older population (Dhainaut et al., 2004; Michelozzi et al., 2004, Schar and Jendritzky, 2004).

These adverse effects resulting from a changing climate will present dilemmas of justice for the global population. Those without the resources to adapt to a changing climate will suffer disproportionately from its effects. It therefore would be a prudent strategy for nations to collectively mitigate further emissions of greenhouse gases into the atmosphere, stabilize concentrations at safe levels, and institute adaptive strategies to deal with the threat. However, lacking a global institution of enforcement on such a regime leaves these efforts to a self-enforcing commitment. Mitigation policies proposed by the IPCC call for regulating greenhouse gas emissions as a pollutant by enacting regulations and standards, taxes and charges, tradable permits, voluntary agreements (VAs), informational instruments, subsidies and incentives, research and development, and trade and development assistance in an effort to reduce global emissions (IPCC (c), 2007).

The projected climate change-related exposures are likely to affect the health of millions of people, particularly those with low adaptive capacity such as the older population. Increases in malnutrition, death due to extreme weather events, frequency of cardiovascular disease from increased ozone, and altered distribution of disease vectors will exacerbate the need for adaptive strategies (IPCC (b), 2007). The UNFCCC considers placing the needs of the most vulnerable first as a strategy for the fairest adaptation. These justice dilemmas will require careful thought by a global society as mitigation and adaptation strategies are developed.

VI. Recommendations for Research

Key recommendations which emerge from our review focus on the need to address the potential adverse health effects on the older population and its heightened vulnerability to climate change. Logical research questions have to do with investigating the mechanism of effects on older people’s health, exploring how they will cope with or adjust to the new environmental conditions, how they can best be educated about risk, and what kinds of interventions (e. g., home modifications) may protect them against threats (such as extreme heat).

The following are some potential research questions (not listed in any order of priority) to serve as a springboard for group discussion:

1. What are trends in migration patterns of older Americans to coastal and other ecologically sensitive areas? What implications do such patterns have for planners and policy makers trying to anticipate the implications of climate change?

2. Which subgroups of the older population are more susceptible to environmental health problems? How can we best establish such differences in risk, and what kind of research is needed to do so?

3. Greater attention to the effects of climate change on vulnerable populations should be made a priority. Leadership at all policy levels is necessary to plan and deliver effective policy to mitigate the negative effects on older populations’ health due to a changing climate. What types of research knowledge are needed to inform and influence policymakers?

4. Older people require better information regarding environmental threats (both those directly related to climate change, as well as more general health impacts). Research is needed on communication strategies around health risk. What types of risk communication work best with older populations? What are the most effective methods of informing older people about possible risks?

5. Similarly, what are the most effective methods of communication to professionals who work with older persons about environmental health risks?

1. Research is needed on evacuation planning for older people (and other vulnerable populations). How can we best promote “accessible evaluation?” What best practices exist in this area? Are registries of vulnerable older persons useful? How can technology (e.g., Geographic Information Systems, Electronic Medical Records) assist in evacuations of older persons?
2. “One size fits all” interventions to mitigate the effects of climate change may not be effective. Interventions should be specific to special populations, and to those with a higher probability of harm. Special attention should be given to older persons with multiple susceptibilities and those who are socially isolated, physically challenged, and geographically dispersed. What kinds of research are needed to illuminate the targeting of interventions?
3. There is anecdotal evidence that some older people resist social services in general, and more specifically assistance around potential disasters. What do we know about resistance to disaster planning, evacuation efforts, etc., and how might such barriers be overcome?
4. To what extent is climate change and its effects a potential motivator for action by older people? Is the threat of possible health effects an issue that would galvanize the older population to action? Given the fact that the oldest old are highly vulnerable, could increased awareness also spur concerned family members to civic engagement on the climate change issue? How might this issue be studied?
5. To what extent do older people contribute to global warming through consumer behavior, car and plane travel, and other sources? What is their contribution in comparison to other age groups? Are there specific ways that pro-environmental behavior can be promoted among older people?