Background:
Alzheimer's disease and Alzheimer's disease-related dementias (AD/ADRD) are prevalent neurodegenerative disorders, posing a critical worldwide public health challenge. Ambient air pollution has been identified as a potential risk factor for AD progression based on toxicological and epidemiological studies. We aimed to evaluate the impacts of air pollution—including fine particulate matter (PM_2·5), nitrogen dioxide (NO₂), summer ozone (O₃), and oxidant—on readmission or death among Medicare enrollees previously hospitalised with an AD/ADRD diagnosis code.

Findings:
Our cohort consisted of 5 544 118 individuals, of whom 4 543 759 (82·0%) died and 3 880 894 (70·0%) were readmitted to the hospital during the study period. The average follow-up times were 3·34 years (SD 2·60) for the mortality cohort and 1·98 years (SD 1·65) for the readmission cohort. In both the mortality and readmission cohorts we found significant associations with each pollutant. For an IQR increase in NO₂, we found a hazard ratio (HR) for mortality of 1·012 (95% CI 1·009–1·015) and an HR for readmission of 1·110 (1·104–1·117). In the readmission cohort, we found an HR of 1·084 (1·079–1·089) for an IQR increase (3·87 μg/m³) in PM_2·5. The results slightly decreased in multi-pollutant models. The results of effect modification for mortality and readmission varied by pollutant, but higher risks were found among Black males and among those eligible for Medicaid in general.

Climate anxiety is a phenomenon that is gaining importance due to the general public’s increased awareness of the worsening climate crisis. At present, climate anxiety is not operationalized consistently across the existing literature. It is important to gain more consensus on the definition and operationalization of climate anxiety to facilitate reliable and generalizable research and to further develop interventions. Content analysis can contribute to this by providing insight into the overlap in the content of climate anxiety measures. With a systematic search, this study identified and analyzed 12 distinct scales measuring climate anxiety. The 119 items covered a total of 57 disparate symptoms. Jaccard indices showed that the mean overlap between symptoms of different climate anxiety scales was generally very low, as was the overlap between pairwise comparisons of climate anxiety scales. These results highlight the lack of uniformity in assessing climate anxiety and the need to properly define and operationalize this concept. The potential reasons for low overlap and how this might impact the reliability and validity of existing measures are discussed. It is critical that future work aims at finding consensus on the definition of climate anxiety (e.g., through a Delphi study) and psychometrically comparing the different questionnaires.