Relationships between macular pigment optical density and cognitive function in unimpaired and mildly cognitively impaired older adults

Low carotenoid status (especially of the xanthophylls, lutein [L], and zeaxanthin [Z]) is common in older adults and has been associated with a number of degenerative diseases of the central nervous system ranging from retina (e.g., macular degeneration) to brain (e.g., Alzheimer's disease). In this study, we tested whether retinal measures of L + Z (macular pigment optical density [MPOD]), used as a surrogate for brain L + Z levels, were related to cognitive function when comparing healthy older adults with mildly cognitively impaired older adults. Twenty-four subjects with mild cognitive impairment were compared with 24 matched controls. Subjects were matched with respect to age, body mass index, ethnicity, sex, and smoking status. Degree of cognitive impairment and cognitive ability was determined via structured clinical interview. MPOD was measured psychophysically. In healthy older adults, MPOD was only related to visual-spatial and constructional abilities (p = 0.04). For subjects with mild cognitive impairment (MCI), however, MPOD was broadly related to cognition including the composite score on the mini-mental state examination (p = 0.02), visual-spatial and constructional abilities (p = 0.04), language ability (p = 0.05), attention (p = 0.03), and the total scale on the Repeatable Battery for the Assessment of Neuropsychological Status (p = 0.03). It is possible that L/Z status may be more strongly related to cognition when individuals are considered with established onset of cognitive decline.