Environment/Climate Change
Acute exposure to extreme summer heat increases risk of hospitalizations among adults with dementia Scott Delaney* Scott Delaney Angela Stegmuller Daniel Mork Danielle Braun Antonella Zanobetti
Background
As climate change accelerates, the frequency of hot summer temperatures will increase, which may impact neurological health. Socially marginalized adults and those with neurodegenerative diseases may be particularly vulnerable, but whether hot summer temperatures increase the risk of symptoms related to Alzheimer’s Disease and related dementias (ADRD) remains understudied. We explored the impact of short-term exposure to extreme summer heat on hospitalization with ADRD diagnosis codes.
Methods
Health data is from adults aged 65+ enrolled in Medicare from 2000-2016. Using exposure data from GridMET, we calculated heat index distributions for May-August in each Koppen-Geiger climate subtype. We used these distributions to convert heat index values for each ZIP code to heat index percentiles for use as our exposure. In a time-stratified case-crossover design, we identified 209,269 cases, defined as first known hospitalization among adults with ADRD. We matched controls on week day, month, and year. We fit 14-day distributed lag nonlinear models using conditional logistic regression and cubic splines with degrees of freedom and knot placement based on AIC. We stratified analyses by climate type and demographic characteristics.
Results
Extreme summer heat indexes were associated with increased ADRD-involved hospitalization risk in some but not all climates. Lag-response relationships suggest effects extend 2-4 days after exposure depending on climate. Thus, the OR of hospitalization after 3 days of sustained exposure to heat indexes in the 99th vs 50th percentile was 1.03 (95% CI 1.02, 1.05) for Temperate zones; 1.03 (1.02, 1.04) for Continental zones; 1.03 (0.99, 1.06) for Arid zones; and 1.02 (0.96, 1.08) for Tropical zones. Importantly, the OR point estimate for Black versus White beneficiaries was approximately 3 times larger.
Conclusion
Extreme heat may increase risk of hospitalization among adults with ADRD and may exacerbate racialized health inequities.
