Retinal microvascular abnormalities and cognitive dysfunction: a systematic review

Objective: To examine the evidence for an association between cognitive impairment or dementia and the presence of retinal microvascular abnormalities. Methods: A systematic review of observational studies identified through searching five electronic databases and reference lists. Studies were required to have both a recognised cognitive function assessment (either a structured neuropsychological test or a clinical evaluation of dementia), and assessment of the retinal microvasculature (either characteristics associated with generalised retinopathy or changes specific to arterioles or venules). Results: 6 studies were included. Studies were clinically and methodologically heterogeneous and of variable quality. Some degree of cognitive impairment was found to be associated with the presence of retinal microvascular abnormalities in all studies, although the extent of the association varied. The presence of retinal vascular signs was mostly associated with poorer verbal memory, mental speed and executive function in the general population, but not consistently associated with other cognitive modalities. Conclusions: There is some evidence suggesting a positive association between retinal microvascular abnormalities and cognitive impairment or dementia in elderly people and in patients with diabetes. Findings are inconclusive, and further better designed studies are required, with standardised and objective retinal vascular assessment and a range of sensitive cognitive tests.