Collaborative research, led by a team at the UCL Institute of Ophthalmology, London, UK, has shown a clear association between a thinner retinal nerve fibre layer (RNFL) and worse cognitive function in individuals without a neurodegenerative disease. The research claims to be the largest study of its kind conducted to date, and the first such study to identify that future decline in cognitive function may also be associated with a thinner RNFL in a large community-based cohort of participants. According to the researchers, the findings may have implications for the “future research, prevention, and treatment of dementia.” The research, which accessed data from 32,038 people in the UK, showed that a thinner RNFL was associated with worse cognitive performance on baseline assessment and that a multivariable regression analysis 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 on 1,251 participants (3.9%) showed that those in the 2 thinnest (RNFL) quintiles were almost twice as likely to have at least 1 test score be worse (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).
As ageing populations have expanded world-wide, age-related disorders have become an increasing healthcare burden, often requiring well-planned strategic and national clinical management programs to optimize care. There is an estimated prevalence of 46 million patients worldwide with dementia – some projections estimate that the prevalence of Alzheimer’s disease, one of the most common forms of dementia, may triple by the year 2050. According to the UK researchers, delaying the onset of dementia by one (1) year is projected to reduce the global prevalence of the disease by 9 million. Consequently, any opportunities to identify dementia as early as possible may have significant public healthcare implications.
The UK research team benefited from the availability of data collated by the UK Biobank, “a prospective, multicenter, community-based study of UK residents aged 40 to 69 years at enrollment who underwent baseline retinal optical coherence tomography (OCT) imaging, a physical examination, and a questionnaire.” A pilot study collected baseline measurements, including cognitive testing, which were repeated in a subset of participants approximately 3 years following enrollment. Analyzing the data, the researchers computed odds ratios (ORs) for cognitive performance showing that when participants in the thickest RNFL quintile were compared to those in the 2 thinnest quintiles, the former were almost twice as likely (odds ratio, 1.92; 95%CI, 1.29-2.85; P < .001) to score worse on at least one cognitive test at follow-up. Furthermore, the researchers were able to suggest that for each quintile of RNFL thinning, there was an 18% increased risk of cognitive decline at 3-year follow-up (95%CI, 8%-29%; P < .001). The researchers concluded that a thinner RNFL is a potential marker for current impaired cognition, and may provide the basis of a screening tool for populations with an increased risk of future cognitive decline. Commenting on the study findings, the researchers stated that “the finding that a thinner RNFL is associated with significant future cognitive decline in a large cohort of people aged 40 to 69 years, drawn from communities around the United Kingdom, consolidates the case for regarding retinal anatomical measures as a useful potential screening test for identifying those at risk of future cognitive loss.”