Population Aging and Heat Exposure in the 21st Century: Which U.S. Regions Are at Greatest Risk and Why?
Climate change has dire consequences for older adults’ health and well-being. Despite extensive research on extreme heat on older adults’ individual-level health and mortality risk, elderly population level heat exposures remain poorly characterized. We remedy this by bringing together age-stratified county-level future population projections for the Shared Socioeconomic Pathway scenarios (SSPs—Streissnig et al 2019), with downscaled and biased corrected temperature projections from the latest generation of global climate models (the NASA NEX Global Daily Downscaled Product CMIP6) for warming scenarios consistent with the SSPs. We estimate current (1995-2014) and projected future (2041-2060) changes in the age 69+ population and heat exposure, both chronic—cooling degree days (CDDs), and acute—the 95th percentile of daily maximum temperature (TMax95), identify the geographic intersection of population aging and increasing heat, and estimate the relative contributions of these factors to changing future heat exposure across the coterminous U.S.
While southern (northern) regions have relatively young (old) populations with more severe (modest) heat exposure, “hotspots” of coincident elevated heat exposure and older populations are concentrated in Florida, Texas and Oklahoma. Warmer southern regions will experience dramatic rises in chronic heat exposures and the 69+ population age fraction. Cooler areas in the Northeast, upper Midwest, and to a lesser extent the Northwest will experience relatively rapid growth in acute heat exposures but relatively slower increases in population aging. Broadly, climate change has a relatively minor effect on the growth of acute elderly heat exposures. However, it accounts for a substantial share of the increase in chronic elderly heat exposures in historically cooler areas such as New England and the Middle Atlantic, and the East and West North Central regions. Conversely, population growth and population aging are larger drivers in the South Atlantic, West and East South Central, and Mountain regions.
The co-occurring trends of population aging and climate change mean that rising numbers of U.S. older adults are at risk of intensifying heat exposure. We estimate county-level variations in older populations’ heat exposure in the early (1995-2015) and mid (2050) 21st century. We identify the extent to which rising exposures are attributable to climate change versus population aging. We estimate older adults’ heat exposure in 3,109 counties in the 48 contiguous U.S. states. Analyses use NASA NEX Global Daily Downscaled Product (NEX-GDDP-CMIP6) climate data and county-level projections for the size and distribution of the U.S. age 69+ population. Population aging and rising temperatures are documented throughout the U.S., with particular “hotspots” in the Deep South, Florida, and parts of the rural Midwest. Increases in heat exposure by 2050 will be especially steep in historically colder regions with large older populations in New England, the upper Midwest, and rural Mountain regions. Rising temperatures are driving exposure in historically colder regions, whereas population aging is driving exposure in historically warm southern regions. Interventions to address the impacts of temperature extremes on older adult well-being should consider the geographic distribution and drivers of this exposure. In historically cooler areas where climate change is driving exposures, investments in warning systems may be productive, whereas investments in healthcare and social services infrastructures are essential in historically hot regions where exposures are driven by growing concentrations of older adults.