Urban heat island exposure and its impact on Alzheimer’s disease and related dementia outcomes among older adults in South Florida - Deaths due to extreme heat are projected to increase by 370% by mid-century, and at the same time, over 13 million Americans will be affected by Alzheimer’s disease and related dementias (ADRD). Our living environments need to adapt to extreme temperatures and protect against urban heat islands—built environments with reduced vegetation and more paved surfaces associated with greater surface temperatures and greater risk of heat-related health effects. This study will bridge significant scientific gaps by investigating ADRD-related impacts from cumulative urban heat island exposure; providing evidence on whether the provision of more greenspaces (offering shade and cooling) may buffer against urban heat island exposure; and investigating the mechanisms linking cumulative urban heat island exposure to ADRD outcomes. Our aims are to: (1) investigate whether recent urban heat island exposure is associated with cognitive function, (2) determine whether cumulative urban heat island exposure is associated with structural MRI biomarkers and longitudinal cognitive decline; and (3) evaluate whether (i) urban heat island exposures are associated with ADRD risk factors (physical inactivity, social isolation, inflammation) (i.e., mechanisms), and (ii) living in greener neighborhoods is associated with lower urban heat exposures and better ADRD outcomes (e.g., slower cognitive decline) (i.e., mitigation). We will create Geographic Information System (GIS) measures of recent and cumulative urban heat island exposure by linking geocoded addresses to land surface temperatures from satellite imagery. These measures will be developed for 500 participants in the Healthy Brain Initiative (HBI), a longitudinal cohort of ≥50-year-olds with no/subjective/mild cognitive impairment from the South Florida region. A subset (n=200) will wear smartwatches to derive GPS/travel behavior and heat exposure data for two 3-week periods (May-October) over a one-year period. Data on older adults (n=9,673) from the Health and Retirement Study will be used to externally validate HBI findings to a national setting (Aims 1-3). This will be the first known study to determine associations between cumulative urban heat island exposure and ADRD risk factors, brain imaging biomarkers, and cognitive outcomes. Providing evidence that supports causal associations between urban heat island exposures and ADRD outcomes and evidencing that greenspaces reduce the harmful influence of heat on ADRD risk would support targeted interventions for heat exposure reduction for ADRD prevention in populations most susceptible to extreme heat.
