Structural and Vascular Abnormalities in Retina Can Signal Cognitive Decline in Type 1 Diabetes

New research from investigators at the Joslin Diabetes Center is shedding light on a new technique for assessing possible cognitive decline in patients with type 1 diabetes.

Funded by groups including the National Institute of Diabetes and Digestive and Kidney Diseases, National Eye Institute, and the National Institutes of Health, results of the study indicate ophthalmic exams using OCT and OCTA scans in patients with type 1 diabetes can provide clinicians with insight into the cognitive health of these patients.

"Since we knew that there were cellular changes in the retina that might reflect changes in the brain, we were interested to see whether imaging techniques that visualize those changes in the retina might be reflective of changes in cognitive functions," said study author Ward Fickweiler, MD, a Joslin postdoctoral fellow, in a statement from the Joslin Diabetes Center.

With the knowledge that proliferative diabetic retinopathy is associated with an increased risk of cognitive impairment, including development of Alzheimer’s disease, a team from Joslin Diabetes Center sought to determine whether routine eye scans could be used to improve identification of patients at risk of cognitive decline. Led by George L. King, MD, Joslin's Chief Scientific Officer, investigators designed their analysis to use data from the Joslin Medalist Study, which allowed them to identify 129 participants for inclusion in their study.

All 129 patients had been living with diabetes for 50 years or longer and data related to both OCT and OCTA scans. For inclusion in the study, patients were required to have undergone validated cognitive testing measures, including assessments of psychomotor speed and immediate and delay memory. Of note, OCT and OCTA scans were used to determine neural retinal layer thicknesses and vascular density for superficial (SCP) and deep retinal capillary plexus (DCP).

Investigators used multivariable modeling in an effort to determine potential associations between structural and vascular abnormalities of the retina with cognitive decline. To limit confounding, investigators used demographic characteristics, glycemic control and metabolic markers, exercise, smoking, and markers of β-cell function as covariates in multivariable models.

Upon analysis, investigators found decreased vessel density of the SCP and DCP were associated with worse delayed memory (DCP, P=.02) and dominant hand psychomotor speed (SCP, P=.01). Additionally, investigators found thinning of the retinal outer nuclear layer was associated with worse psychomotor speed in both nondominant (P=.01) and dominant hands (P=.05). Investigators also found outer plexiform layer thickness was associated with delayed memory (P=.04).

Investigators pointed out these results may not be applicable to all populations of patients with type 1 diabetes as the cohort of patients within the Joslin Medalist Program display low levels of complications with long-term type 1 diabetes compared to other populations.

"It is possible that in the Medalists, a shared mechanism alters the progression of the early stages of retinal and brain neurodegeneration, and provides protection against both PDR and Alzheimer's disease," Fickweiler speculated.

The study, “Association of Cognitive Function and Retinal Neural and Vascular Structure in Type 1 Diabetes,” was published in The Journal of Clinical Endocrinology and Metabolism.