A thin macular retinal nerve fiber layer is associated with decline in cognitive function in older adults, according to a study from South Korea reported in JAMA Ophthalmology.¹

The objective of the current study was to examine a potential link between retinal layer thickness and impairment of cognition and cognitive decline later on in life. For this, the researchers recruited 430 individuals, aged ≥60 years (mean age 76.3 years) from two population-based longitudinal cohort studies: the Korean Longitudinal Study on Health and Aging and the Longitudinal Study on Cognitive Aging and Dementia. Nearly half were female (48.6%). Of these, 215 completed the follow up for 5.4 years (mean). The thickness of the retinal layers in the macula was measured with the aid of spectral-domain optical coherence tomography (OCT) at baseline and at follow-up. Thickness of peripapillary retinal nerve fiber layers (RNFLs) and the subfoveal choroid were also measured. Neuropsychological evaluation was done via Consortium to establish a Registry for Alzheimers Disease Assessment Packet (CERAD-K) (Korean version) and the Mini-Mental State Examination (MMSE) scores at baseline and at follow-up.

Results from the study showed that a thinner total macular retinal nerve fiber layer (RNFL) at baseline was associated with a decrease in the two cognitive test scores, CERAD (p = .003) and MMSE (p = .01), during the follow-up period. Patients who had total macular retinal nerve fiber layer thickness less than the lowest quartile i.e., less than 231 μm, exhibited marked decline in the cognitive scores (CERAD and MMSE) compared to those with RNFL thickness above this threshold. The annual cognitive decline on the CERAD score in patients with baseline macular RNFL below the lowest quartile was 3.8 points versus 2.2 points in patients with RNFL above the lowest quartile. On MMSE, the corresponding figures were 0.89 vs 0.58.

Those with the thinnest total macular RNFL showed the greatest decline in cognitive scores. The prevalence of cognitive impairment and Alzheimer disease was also higher in these patients. Similar findings were observed for outer as well as inner macular RNFL thickness. No differences were noted in the cognitive score and RNFL thickness with regard to APOE ε4 status.

This study found that among the retinal layers, only the macular RFNL correlated with cognitive scores. It has documented an association between baseline macular retinal nerve fiber layer thickness measured with OCT and cognitive function scores at baseline and future cognitive decline. It further suggests the use of macular retinal nerve fiber layer thickness as a noninvasive biomarker for evaluating alterations in cognitive function in older adults. A thinner macular RNFL therefore may be predictive of cognitive decline, suggest the authors, who have called for larger studies to further verify these observations.

Reference

1. Kim HM, et al. Association between retinal layer thickness and cognitive decline in older adults. JAMA Ophthalmol. 2022 May 26:e221563. doi: 10.1001/jamaophthalmol.2022.156.