Diabetic Retinopathy and Cognitive Decline in Older People with Type 2 Diabetes

Abstract

Objective: Cerebral microvascular disease associated with type 2 diabetes (T2D) may exacerbate the effects of aging on cognitive function. A considerable homology exists between the retinal and cerebral microcirculations. An hypothesized association between diabetic retinopathy (DR) and cognitive decline was examined in older people with T2D. Research design and methods: In our study 54 men and women aged 60-75 years with T2D underwent standard standard retinal examination and a battery of cognitive function tests. A general cognitive ability score (g) was generated by principal components analysis. The Mill-Hill Vocabulary Scale was used to estimate premorbid cognitive ability. DR was graded using Diabetic Retinopathy Scale. Results: A significant relationship was observed with increasing severity of DR (none, mild, and moderate to severe) for most cognitive measures. Participants with moderate-to-severe retinopathy had the worst g and the worst performances on the individual tests. There was a significant interaction between sex and retinopathy for g. In male subjects, the associations of retinopathy with g (and with tests of verbal fluency and processing speed but not memory and nonverbal reasoning) persisted (P < 0.05) when further adjusted for vocabulary (to estimate lifetime cognitive decline), depression, cardiovascular risk factors, and macrovascular disease. Conclusions: DR was independently associated with estimated lifetime cognitive decline in older men with type 2 diabetes, supporting the hypothesis that cerebral microvascular disease may contribute to their observed accelerated age-related cognitive decline. A sex interaction with stronger findings in men requires further confirmation.