Trajectories of peripheral interleukin-6, structure of the hippocampus, and cognitive impairment over 14 years in older adults

Abstract

We aimed to investigate if trajectory components (baseline level, slope and variability) of peripheral IL-6 over time were related to cognitive impairment and smaller hippocampal volume, and if hippocampal volume explained the associations between IL-6 and cognitive impairment. Multivariable regression models were used to test the association between IL-6 trajectory components with change in neuroimaging measures of the hippocampus, and with cognitive impairment among 135 older adults (70–79 years at baseline) from the Healthy Brain Project over 14 years. IL-6 variability was positively associated with cognitive impairment (OR = 5.86, 95% CI:1.24, 27.61) and with greater decrease per year of gray matter volume of the hippocampus (β=−0.008, SE=0.004, p=0.03). After adjustment for hippocampal volume, the odds ratio of cognitive impairment decreased for each unit of IL-6 variability, and confidence intervals widened (OR=4.36, 95% CI: 0.67, 28.29). Neither baseline levels nor slopes of IL-6 were related to cognitive impairment or hippocampal volume. We believe this has potential clinical and public health implications by suggesting adults with stable levels of peripheral IL-6 may be better targets for intervention studies for slowing or preventing cognitive decline.

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