Long term associations of climatic factors on cognition in olderadults: Results from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Cohort

Abstract

"Background: Evidence suggests that short term exposures to extreme heat and/or cold are associated with declines in cognition among older adults. However, the effect of long term exposures are not well understood. Methods: The Reasons for Geographic and Racial Differences in Stroke (REGARDS) study is a nationwide cohort study exploring regional and racial differences in stroke and cognitive function over time. ~30,000 people from all areas of the US were enrolled at age 45. Word List Learning (WLL) and Word List Delayed Recall (WLD) tests were administered on a yearly basis. Continuous cognition scores were produced using factor analysis based methods and applied to each measured time point for each individual. Associations of cognition with the number of extreme hot and cold days relative to region were tested using regression models of the continuous measure of cognition within a directed non linear Distributed Lag Non-linear Modelling framework. Results: Cognition data was available for 20,091 people with a mean age of 64.6 years over miltiple time points. Of these, 39.2 percent were Black. On average, respondents experienced 25.4 and 14 extremely hot and cold days the year previous to the last date of survey. Cognition was significantly and negatively impacted by same year exposure to increased numbers of extreme heat days. No association of long term heat and/or cold exposure was found for exposure days greater than one year, or for exposure to cold or precipitation for all time periods tested. Conclusions: Evidence suggests that the greatest impacts of temperature on cognition occurs within one year of exposure. Future work should explore the potential role of climate change in increasing incidence of cognitive decline in older adults.