Association of Retinal Nerve Fiber Layer Thinning With Current and Future Cognitive Decline: A Study Using Optical Coherence Tomography

Abstract

Importance: Identifing potential screening tests for future cognitive decline is a priority for developing treatments for and the prevention of dementia.

Objective: To examine the potential of retinal nerve fiber layer (RNFL) thickness measurement in identifying those at greater risk of cognitive decline in a large community cohort of healthy people.

Design, setting, and participants: UK Biobank is a prospective, multicenter, community-based study of UK residents aged 40 to 69 years at enrollment who underwent baseline retinal optical coherence tomography imaging, a physical examination, and a questionnaire. The pilot study phase was conducted from March 2006 to June 2006, and the main cohort underwent examination for baseline measures from April 2007 to October 2010. Four basic cognitive tests were performed at baseline, which were then repeated in a subset of participants approximately 3 years later. We analyzed eyes with high-quality optical coherence tomography images, excluding those with eye disease or vision loss, a history of ocular or neurological disease, or diabetes. We explored associations between RNFL thickness and cognitive function using multivariable logistic regression modeling to control for demographic as well as physiologic and ocular variation.

Main outcomes and measures: Odds ratios (ORs) for cognitive performance in the lowest fifth percentile in at least 2 of 4 cognitive tests at baseline, or worsening results on at least 1 cognitive test at follow-up. These analyses were adjusted for age, sex, race/ethnicity, height, refraction, intraocular pressure, education, and socioeconomic status.

Results: A total of 32 038 people were included at baseline testing, for whom the mean age was 56.0 years and of whom 17 172 (53.6%) were women. A thinner RNFL was associated with worse cognitive performance on baseline assessment. A multivariable regression controlling for potential confounders showed that those in the thinnest quintile of RNFL were 11% more likely to fail at least 1 cognitive test (95% CI, 2.0%-2.1%; P = .01). Follow-up cognitive tests were performed for 1251 participants (3.9%). Participants with an RNFL thickness in the 2 thinnest quintiles were almost twice as likely to have at least 1 test score be worse at follow-up cognitive testing (quintile 1: OR, 1.92; 95% CI, 1.29-2.85; P < .001; quintile 2: OR, 2.08; 95% CI, 1.40-3.08; P < .001).

Conclusions and relevance: A thinner RNFL is associated with worse cognitive function in individuals without a neurodegenerative disease as well as greater likelihood of future cognitive decline. This preclinical observation has implications for future research, prevention, and treatment of dementia.

Figure 1.. Proportion of UK Biobank Participants Exhibiting a Cognitive Deficit at Baseline Testing

The cross-sectional data showing the proportion (with 95% CIs) of 32 038 UK Biobank participants with a cognitive deficit (a failing score on 2 or more of 4 tests), according to quintile of retinal nerve fiber layer (RNFL) thickness measured in the outer nasal retinal subfield by optical coherence tomography.

Figure 2.. Proportion of UK Biobank Participants Exhibiting a Decline in Cognitive Function on Repeat Assessment

The number of cognitive tests with worse scores on follow-up testing was significantly associated with baseline retional nerve fiber layer (RNFL) thickness. The regression coefficient was 1.2 μm per test failed (P < .001). After controlling for potential confounders, including age, sex, race/ethnicity, Townsend deprivation index, height, refraction, and intraocular pressure, the regression coefficient was 1.1 μm per test failed (P < .001).