Association of cognitive functioning with retinal nerve fiber layer thickness
PURPOSE. The brain areas that are responsible for cognitive functioning have the same embryonic origin as the retina. The association between cognitive functioning and retinal nerve fiber layer (RNFL) thickness was assessed in a large, population-based sample. METHODS. Neuropsychological and ophthalmic examinations were performed in 1485 healthy individuals (mean age, 46 years; range, 18 - 85) from the Erasmus Rucphen Family (ERF) study, a study in a genetic isolate from the Netherlands. Different domains of cognitive functioning were assessed with the Dutch Adult Reading Test, the Rey Auditory Verbal Memory Test, semantic fluency, the Trail-Making Test, the Stroop Color-Word Test, and Block Design. RNFL thickness was measured with scanning laser polarimetry. The association between cognitive test scores and peripapillary RNFL thickness was studied with linear regression analyses, adjusting for age, sex, level of inbreeding, and refractive error. RESULTS. After adjustment for confounders, a better cognitive performance was significantly associated with a thicker RNFL in all tests (P < 0.03) except for the Stroop Color-Word Test (P = 0.15). RNFL thickness explained up to 2.8% (R2= 0.028) of the total variance in cognitive test scores. The association diminished in age groups beyond 40 years. CONCLUSIONS. The present study shows that cognitive functioning is associated with RNFL thickness in healthy young individuals. The lack of association in older individuals suggests that loss of neurons in the cerebrum and retina is not concomitant and may have different origins.