Severe diabetic retinopathy poses increased cognitive impairment hazard

Patients with moderate or worse diabetic retinopathy (DR) are at much higher odds of developing cognitive impairment, according to a Singapore study.

“Importantly, these findings were independent of key risk factors of cognitive impairment, such as duration of diabetes, HbA1c, education, refractive error, cardiovascular disease (CVD) and visual acuity,” the investigators said.

The study included 682 diabetic participants (mean age, 67.3 years; 44.4 percent female; 30.4 percent Chinese) from the Singapore Epidemiology of Eye Disease Study. DR was present in 199 participants (29.2 percent), among whom 142 (20.8 percent) had minimal/mild disease and 57 (8.4 percent) had moderate or worse disease.

Over the 6-year follow-up, 40 participants (5.9 percent) were found to have cognitive impairment based on Abbreviated Mental Test screening, corresponding to an incidence rate of 5.9 percent. This group of individuals was older, more likely to be female, of Indian ethnicity, had lower education and poorer presenting distance visual acuity (p-all<0.05). [Br J Ophthalmol 2019;103:1605-1609]

In multivariate analysis regression models, participants with any DR were more than twice as likely as those without the diabetic eye disease to have cognitive impairment (odds ratio [OR], 2.32, 95 percent CI, 1.07–5.03). The odds were threefold higher in participants with moderate or worse DR (OR, 3.41, 1.06–11.00).

“Although these results need to be interpreted with caution due to the small number of individuals with incident CI, the data suggest that the significant diabetes–cognitive impairment relationship observed in previous studies may have been driven by the presence of diabetic microvascular complications in these individuals,” according to the investigators, stressing that larger cohort studies are needed to verify the present data and establish underlying mechanisms.

Given that retinal and cerebral small vessels share similar embryological origin, size, structure and physiological characteristics, including the blood-brain and blood-retinal barrier, the investigators speculate that retinal abnormalities in DR may also signal abnormalities within the blood-brain barrier, leading to cognitive decline. [J Anat 2005;206:319-348]

“Our findings highlight the importance of systematic preventative strategies such as regular eye screening, to prevent and slow DR progression, notably advanced DR,” the investigators said.

Clinicians managing patients with DR should therefore consider incorporating cognitive impairment monitoring and treatment, which in turn can improve the quality of life in both patients and their caregivers, they added.