Abstract

Objective: To determine whether circulating levels of the inflammatory markers C-reactive protein (CRP), interleukin (IL)-6, and tumour necrosis factor (TNF)-α are associated with cognitive ability and estimated lifetime cognitive decline in an elderly population with type 2 diabetes mellitus.

Research Design and Methods: Cross sectional study of 1066 men and women aged 60 to 75 years with type 2 diabetes, living in Lothian, Scotland (the Edinburgh Type 2 Diabetes Study). Seven cognitive tests were used to measure abilities in memory, non-verbal reasoning, information processing speed, executive function, and mental flexibility. The results were used to derive a general intelligence factor, g. A vocabulary-based test was administered as an estimate of peak prior cognitive ability.. Results on the cognitive tests were assessed for statistical association with inflammatory markers measured in a venous blood sample at the time of cognitive testing.

Results: Higher IL-6 and TNF-α levels were associated with poorer age- and sex-adjusted scores on the majority of the individual cognitive tests, and with g with standardised regression coefficients −0.074 to −0.173 (p<0.05). After adjusting for vocabulary, education level, cardiovascular dysfunction, duration of diabetes and glycaemic control, IL-6 remained associated with three of the cognitive tests and with g.

Conclusions: In this representative population of people with type 2 diabetes elevated circulating levels of inflammatory markers were associated with poorer cognitive ability. IL-6 levels were also associated with estimated lifetime cognitive decline.