Association of interleukin-6 rs1800796 polymorphism with reduced cognitive performance in healthy older adults

© 2018 Elsevier B.V. With increasing life expectancy, age-associated cognitive impairment is an escalating problem worldwide. Inflammation is one of the features that characterises cognitive decline and can stimulate neurodegeneration. Interleukin 6 (IL-6) is a cytokine frequently associated with a pro-inflammatory phenotype and increased levels have been associated with the pathogenesis of dementia. The rs1800796 polymorphism in the promoter region of IL-6 gene was previously shown to influence IL-6 expression and therefore we hypothesised this gene polymorphism would be associated with IL-6 plasma levels and cognitive performance of older adults. The present study investigated the association of the rs1800796 polymorphism on plasma IL-6 levels and cognition in healthy older adults (n = 207, 74.6 ± 3.4 years, 51% female) that participated in a Pan-European project (MyoAge). The participants were assessed for working memory capacity, executive functioning, episodic memory and global cognition using the Cambridge Neuropsychological Test Automated Battery CANTAB. Fasting plasma IL-6 levels were measured by ELISA and genotyping was performed using the KASP assay. Results showed that the rs1800796 polymorphism was in Hardy-Weinberg equilibrium (P =.16) with the minor allele (C) showing a frequency of 6.3%. There were no differences in plasma IL-6 concentrations between the GG-homozygotes and C-allele carriers (P =.22). The C-allele carriers performed worse on a measure of executive functioning (P =.035) and had lower global cognitive scores (P =.045), compared to GG-homozygotes. These differences remained significant after accounting for age, sex and prior cognitive abilities (P