Abstract
Inflammation is suspected to play a role in neurodegeneration and is associated with worse memory and smaller medial temporal volumes in controls. Many of the studies, however, have been cross-sectional and little is known about longitudinal changes in cognition due to inflammation. Our objective was to determine if baseline levels of inflammation predicted a steeper slope of cognitive decline longitudinally. Participants were cognitively normal, community dwelling, older adults (mean age = 73.28) followed over multiple visits spanning 4 to 6 years. Participants underwent a fasting blood draw and had their plasma analyzed for interleukin-6 (IL-6) using the Mesoscale platform. At each timepoint, participants completed a series of computerized reaction time tests that yielded a single composite processing speed score. The IL-6 values were log transformed and slope values of the processing speed scores were calculated using linear mixed models. 199 participants were included in this analysis.
Higher baseline IL-6 levels predicted greater increases in processing speed slope (p<.01), while controlling for age and baseline processing speed. These findings suggest that higher levels of systemic inflammation are associated with increased rates of cognitive slowing over time in healthy older adults. These results highlight the importance of inflammation in cognitive aging and the need for further research to elucidate the exact relationship between markers of inflammation and cognitive decline.