Objective:

To investigate the regional impact of local heat stress on Alzheimer’s disease and related dementias (ADRD)

Background:

ADRD is a leading cause of hospitalization among older adults and disease severity may be exacerbated by environmental stressors, including extreme temperature. 

Design/Methods:

Using a time-stratified case-crossover design, we identified beneficiaries in 2018 Medicare claims data who were hospitalized due to ADRD, defined as an ICD-10 diagnosis code in the first 10 positions on the claim, from April-October. We classified the case day as the ADRD admission date and controls days were matched on the same year, month, and day of the week. We used the latitude and longitude of the beneficiaries’ residential zip+4 to link the 2018 average daily temperature obtained from the National Oceanic and Atmospheric Administration. Temperature exposure was classified using location-specific percentiles, with the 50th percentile representing typical temperatures. We used a distributed lag nonlinear model within conditional logistic regression framework to assess the association between temperature and ADRD hospitalizations. 

Results:

We identified 101,917 case days and 349,359 matched control days. Across the United States, relative to the 50th percentile, exposure to extreme heat (99th percentile) was associated with an increased odds of ADRD hospitalization two days later (OR=1.12 [95% CI: 1.06–1.18]). The impact of heat was greater among beneficiaries aged 81 years and older (OR=1.22 [95% CI: 1.12-1.32]), white (OR=1.12 [95% CI: 1.06-1.19]), and dual Medicare and Medicaid (OR=1.24 [95% CI: 1.14-1.36]). Regional analysis indicated highest heat-related ADRD hospital admissions occurred in the South (OR=1.11 [95% CI: 1.01-1.20]). 

Conclusions:

Heat exposure was associated with a higher odds of ADRD hospital admission two days following, with the greatest impact on those >85 and those living in the South. This study may inform efforts to mitigate heat-related morbidity in individuals living with ADRD amid rising global temperatures.