Carotenoids and Retinoids (CARIG)
Individuals with multiple sclerosis (MS) often suffer a progressive loss in visual and cognitive function. While the exact reason for the cognitive decline in MS is unknown, generalized neurodegeneration of the central nervous system has been associated with lower carotenoid levels. Carotenoids have antioxidant effects that could support nerve health and be protective against cognitive decline. Carotenoids are also found in high concentration within the center of the retina, or macula. Their role in the brain may be related to their role in the eye and vision health. We investigated the correlation among macular carotenoids, retinal and nerve fiber layer thickness, and cognitive function in patients with MS.
Subjects included persons diagnosed with MS between 45-64 years (N=29) living in Illinois. Carotenoid accumulation, defined as macular pigment optical density (MPOD), was measured using heterochromatic flicker photometry. Optical coherence tomography (Heidelberg Engineering, Germany) was used to assess total macular volume (TMV), central foveal (CF), and retinal nerve fiber layer thickness (RNFL). Cognitive function was assessed using an Eriksen flanker task for attentional control with event-related brain potentials.
Results : While MPOD was not correlated with TMV (Rho=0.23, p=0.14), CF (Rho< -0.01, p=0.50), or RNFL (Rho=0.19, p=0.19), MPOD was correlated with faster congruent (Rho=-0.34, p=0.04) and incongruent reaction time (Rho=-0.33, p=0.04) and faster congruent (Rho=-0.52, p< 0.01) and incongruent (Rho=-0.37, p=0.04) P2 latency. RNFL was positively correlated with incongruent accuracy (Rho=0.41, p=0.02) and inversely related to incongruent P2 latency (Rho=-0.41, p=0.05), N2 congruent (Rho=-0.46, p=0.03), and incongruent (Rho=-0.47, p=0.03) amplitude. Additionally, RNFL was inversely related to congruent (Rho=-0.51, p=0.02) and incongruent (Rho=-0.54, p=0.01) P3 amplitude. Larger TMV was related to faster congruent (Rho=-0.43, p=0.04) and incongruent P2 latency (Rho=-0.48, p=0.02). CF was not correlated with any of the cognitive task outcomes.
Macular pigmentation and markers of retinal and optic nerve health may positively influence cognitive function in MS. However, MPOD and OCT measures were not correlated, suggesting that macular carotenoids, and retinal and optic nerve thickness may exert independent benefits for cognitive function.
Funding Sources : This work was funded by Pilot Research Grant from the National Multiple Sclerosis Society.