Heatwaves, hospitalizations for Alzheimer's disease, and postdischarge deaths: A population-based cohort study

Abstract Background Available data on the effects of heatwaves on hospitalizations and postdischarge status of Alzheimer's disease patients are very scarce. Methods We used data from a retrospective cohort study which included Alzheimer's disease patients who were hospitalized from 1st January 2005 to 31st December 2013 in Brisbane, Australia, and died within two months after they were discharged. A time-stratified case-crossover design using conditional logistic regression was employed to quantify the effects of heatwaves on hospitalizations and postdischarge deaths due to Alzheimer's disease. A case-only design was used to assess the modification effects of age, sex, and community-level vegetation and Socio-Economic Indexes for Areas (SEIFA) on heatwave effects. Results There were 907 hospitalizations in the study period, and 307 patients died within two months after discharge. Hospitalizations and postdischarge deaths due to Alzheimer's disease increased by 51% (95% confidence interval (CI): 2%, 126%) and 269% (95% CI: 76%, 665%), respectively, during middle-intensity heatwaves (i.e., 95th percentile & ≥2 days). The magnitude of heatwave effect on postdischarge deaths increased dramatically when heatwave intensity increased from 95th percentile to 97th percentile. People who lived in communities with low-level vegetation were more vulnerable to heatwave effect on hospitalizations for Alzheimer's disease than those who lived in communities with high-level vegetation (relative risk: 3.05, 95% CI: 1.16, 7.98). Conclusion Heatwaves increased the risk of hospitalizations for those living with Alzheimer's disease, and increased the risk of postdischarge deaths of Alzheimer's disease patients. Increasing urban greenness may ease heat-related Alzheimer's disease burden.