Macular Ganglion Cell-Inner Plexiform Layer as a Marker of Cognitive and Sensory Function in Midlife

Abstract

Background Neurodegenerative diseases are public health challenges in aging populations. Early identification of people at risk for neurodegeneration might improve targeted treatment. Noninvasive, inexpensive screening tools are lacking but are of great potential. Optical coherence tomography (OCT) measures the thickness of nerve cell layers in the retina, which is an anatomical extension of the brain and might be indicative of common underlying neurodegeneration. We aimed to determine the association of macular ganglion cell-inner plexiform layer (mGCIPL) thickness with cognitive and sensorineural function in midlife. Method This cross-sectional study included 1,880 Beaver Dam Offspring Study participants (aged 27–93 years, mean 58) who participated in the 10-year follow-up examination. We assessed cognitive function and impairment, hearing sensitivity thresholds and impairment, central auditory processing, visual impairment, and olfactory impairment. We measured mGCIPL using the Cirrus 5000 HD-OCT Macular Cube Scan. Multivariable linear and logistic regression models adjusted for potential confounders were used to determine associations between mGCIPL thickness and cognitive and sensorineural functions, as well as for comparing participants with a thin mGCIPL (1 SD below average) to the remainder in those functions. Results Thinner mGCIPL was associated with worse cognitive function, worse central auditory function, and visual impairment. We found an association of mGCIPL thickness with hearing sensitivity in women only and no association with impairment in hearing, olfaction, and cognition. Results on the thin group comparisons were consistent. Conclusions mGCIPL thickness is associated with cognitive and sensorineural function and has the potential as a marker for neurodegeneration in middle-aged adults.

The Association of Psychological Well-Being With Sensory and Cognitive Function and Neuronal Health in Aging Adults

“…When necessary, masking was done. The pure-tone average (PTA) of air-conduction thresholds at .5, 1, 2, and 4 kHz in decibel hearing level (dB HL) for each ear was used to measure hearing sensitivity, with impairment defined as PTA > 25 dB HL (Merten, Paulsen, et al, 2020). Higher-order auditory function was assessed with two additional hearing tests.…”

“…The competing message (single male speaker) was added at a level 8 dB HL below the female speaker’s level in that same ear (Wiley et al, 1998; Wilson et al, 1990). The percentage of correctly repeated digits from both ears in the free recall condition was the DDT outcome and the percentage of correctly repeated words was the WRCM outcome (Merten, Paulsen, et al, 2020).…”

“…A picture board including the eight odorants and additional 12 distractor items was used to aid identification (verbal response or pointing on item on picture board). The number of correctly identified odors was summed and impairment defined as < 6 out of eight correct (Merten, Paulsen, et al, 2020).…”

“…We conducted a neurocognitive test battery consisting of: Trail-Making Tests A and B (TMTA, TMTB), modified Rey Auditory Verbal Learning Test (AVLT), Digit Symbol Substitution Test (DSST), and Verbal Fluency Test (VFT) measuring the cognitive domains of attention, speed, executive function, memory, and verbal fluency (Merten, Paulsen, et al, 2020). Participants were allowed to use assistive devices when performing cognitive tasks (their own glasses and/or hearing aids and we provided reading glasses and/or a Pocket Talker (Pocket Talker Pro TM , Williams Sound, Eden Prairie, MN) if they needed them).…”

“…Sensory and cognitive declines might influence each other over the lifespan and are affected by neurodegeneration, sharing common risk factors (Albers et al, 2015; Merten, Fischer, et al, 2020; Pronk et al, 2019; Schubert et al, 2019). Recently, retinal nerve cells, and, specifically, macular ganglion cell inner-plexiform layer thickness (mGCIPL) was found to be associated with sensorineural (hearing, vision, and olfactory function) and cognitive function and has been discussed as a marker of neuronal health (Merten, Paulsen, et al, 2020; Ward et al, 2020). Neurodegenerative processes start in midlife, decades before clinical symptom onset, indicating a need for early intervention and prevention (Jack et al, 2013).…”