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Thermoregulatory Stress and the Ageing Mind: Investigating Environmental High Heat Exposure as a Risk Factor for Dementia
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Helzner, Elizabeth, Geer, Laura, Meyers, Jacquelyn, Barr, Peter
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Summer 2025
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Background
As populations age globally, the health effects of extreme heat exposure are an increasing
public health concern. This study examines the association between cumulative high heat exposure
and the prevalence of Alzheimer’s Disease and Related Dementias (ADRD) and Mild Cognitive
Impairment (MCI) among U.S. adults.
Methods
Data were obtained from the All of Us Research Program (n = 286,767). Heat exposure
was assessed using data from the CDC’s National Environmental Public Health Tracking Network
and mapped to 3-digit ZIP codes. Two exposure metrics were examined: (1) maximum
temperature and (2) maximum heat index. High heat exposure was defined as the total number of
extreme heat days (≥2 consecutive days with a maximum heat index above the 90th percentile for
May–September) occurring within multi-day heat events from 2019 to 2023. ADRD/MCI
diagnoses and medical comorbidities (cardiovascular disease, cerebrovascular disease, type 2
diabetes, chronic obstructive pulmonary disease, hearing impairment, and depression) were
identified from electronic health records. Demographics, smoking, alcohol use, and social isolation
were measured via survey. Socioeconomic status (SES) was assessed at both the individual level,
using educational attainment, and at the community level, using the Area Deprivation Index (ADI).
Logistic regression models estimated associations between high heat exposure and ADRD/MCI
risk, adjusting for demographic, medical, and socioeconomic factors. Mediation analysis examined
the role of SES and social isolation.
Results
Each additional extreme heat day was associated with a 0.39% increase in ADRD/MCI
odds (95% CI: 1.0026–1.0051) when measured by maximum temperature, and a 0.58% increase
(95% CI: 1.0044–1.0071) when measured by maximum heat index. Exposure to 10 extreme heat
days within multi-day heat events was associated with approximately a 4% increase in the odds of
ADRD/MCI when measured by maximum temperature, and approximately a 6% increase when
measured by maximum heat index. These findings indicate that sustained heat exposure has a
cumulative impact on cognitive risk. The association was stronger when exposure was assessed
using heat index rather than temperature alone, suggesting that humidity exacerbates heat-related
cognitive risks. Mediation analysis found that ADI accounted for 8.6%–9.6% of the total effect;
however, high heat exposure remained a significant independent risk factor for ADRD/MCI.
Neither educational attainment (as a proxy for individual-level SES) nor social isolation
significantly mediated or moderated the observed associations.
Discussion
These findings highlight an association between sustained extreme heat exposure and
ADRD/MCI, with stronger effects observed when using heat index, suggesting humidity may
exacerbate heat-related cognitive vulnerability. Area deprivation partially mediated this
association, reinforcing how environmental and social inequities jointly shape cognitive health.
Older adults are particularly vulnerable, and disparities in access to cooling resources may
compound these risks. The urban heat island effect may further amplify exposure, underscoring
the need for targeted public health interventions, such as early warning systems, urban planning
strategies, and equitable access to cooling. Increasing heat exposure calls for public health
approaches that recognize its potential impact on cognitive decline, especially among structurally
disadvantaged populations. Given the absence of disease-modifying treatments for ADRD/MCI,
addressing modifiable environmental risks remains essential to protect cognitive health in an
ageing population
Citation
Mosaad, A. (2025) Thermoregulatory Stress and the Ageing Mind: Investigating Environmental High Heat Exposure as a Risk Factor for Dementia. [Doctoral Dissertation, SUNY Downstate Health Sciences University]. SUNY Open Access Repository. http://hdl.handle.net/20.500.12648/16548