Particularly Black older adults and those living in poor neighborhoods
Cumulative exposure to extreme heat can trigger a cascade of events in the brain
Prof. LEE, HAENA
Prof. Haena Lee and colleagues published a study in the Journal of Epidemiology and Community Health(IF: 6.3) on the impact of cumulative exposure to extreme heat on cognitive decline among vulnerable groups—particularly Black older adults and those living in poor neighborhoods.
The study, one of the first to investigate the decade-long consequences of extreme heat, finds that cumulative exposure to extreme heat can undermine cognitive health, but it does so unequally across the population.
July 2023 was the hottest month on record. Extreme heat is the leading cause of weather-related deaths in the U.S., claiming more lives each year than hurricanes, tornadoes, and lightning combined. Young children and older adults are particularly vulnerable to heat-related illnesses such as heat exhaustion and heat stroke.
Recent studies suggest that high temperatures may hurt cognitive function, but these studies tend to look at a snapshot of someone’s cognition at a single time point following brief exposure to heat. Less is known about the long-term consequences of heat on cognitive health.
As heat waves become more frequent and intense due to climate change and urban heat islands, Lee and her colleagues sought to understand the connection between extreme heat exposure and cognitive decline. They analyzed data from nearly 9,500 U.S. adults ages 52 and older surveyed over a 12-year period (2006-2018) as part of the Health and Retirement Study conducted by the University of Michigan Institute for Social Research, which measures participants’ cognitive function over time.
The researchers also looked at socioeconomic measures of the neighborhoods where participants lived. In addition, they calculated participants’ cumulative exposure to extreme heat (the number of days in which the heat index reached or exceeded a location-specific threshold) during this 12-year period based on historical temperature data from the CDC’s National Environmental Public Health Tracking Network.
They found that high exposure to extreme heat was associated with faster cognitive decline among residents of poor neighborhoods, but not for those in wealthier neighborhoods. Moreover, cumulative exposure to extreme heat was associated with faster cognitive decline among Black older adults, but not white or Hispanic older adults.
One possibility is that affluent neighborhoods tend to have resources that can help in a heat wave—things like well-maintained green spaces, air conditioning, and cooling centers. In disadvantaged neighborhoods, these resources may not exist. Another explanation for this pattern of findings is that Black older adults may have disproportionately experienced systemic disadvantages throughout their lives due to structural racism, segregation, and other discriminatory policies, all of which may affect cognitive reserve.
The researchers urge local governments and health officials to develop policies and tools that identify residents who are susceptible to extreme heat, empower at-risk communities, map their specific needs, and develop targeted support and increased communication with these populations.
Paper: Cumulative exposure to extreme heat and trajectories of cognitive decline among older adults in the USA
•Journal: Journal of Epidemiology and Community Health
•Author: Haena Lee, Eunyoung Choi, Virginia Chang