Lower serum carotenoid levels are associated with incident cognitive decline independent of traditional risk factors in a prospective study of older men from Northern Ireland

Abstract Background Nutritional influences, and antioxidant status in particular, have been implicated in the aetiology of cognitive decline. This study investigated the neuroprotective effects of serum antioxidants in a prospective cohort of older men to identify associations with cognitive outcomes, independent of traditional risk factors. Method This cohort study included 873 Northern Irish men nested within PRIME (Prospective Epidemiological Study of Myocardial Infarction) who were followed‐up for at least 15 years. Mini Mental State Examination (MMSE) was carried out at baseline. The Addenbrooke’s Cognitive Examination‐R and MMSE were carried out at follow‐up. A consensus diagnosis of normal cognition for age, mild cognitive impairment (MCI) or dementia was made using accepted clinical criteria. Serum concentrations of retinol, two forms of vitamin E (α‐ and ϒ‐tocopherol) and six carotenoids measured from baseline samples were quantified by high‐performance liquid chromatography and assessed by multiple logistic regression analyses. Result The case definition included the 163 men characterised with MCI and 46 men with dementia; 664 participants were considered cognitively normal controls (Table 1). In unadjusted analyses, serum levels of the carotenoids α‐carotene, β‐carotene, lycopene and β‐cryptoxanthin were significantly lower in MCI/dementia cases than controls, in contrast to ϒ‐tocopherol, which was significantly higher (Table 2). Following adjustment for traditional risk factors including height, APOε4 genotype, diastolic blood pressure, smoking status and the presence of (pre)diabetes or depression, the effect size of those carotenoids significant in the unadjusted analysis was attenuated somewhat; only α‐carotene remained significantly associated with MCI/dementia (odds ratio = 0.55; confidence interval: 0.31‐0.99; Table 2). Conclusion Our data implicates lower levels of serum carotenoids as potential early biomarkers of MCI/ dementia before overt manifestation of symptoms, independent of traditional risk factors. These findings are consistent with hypotheses supportive of a neuroprotective role of dietary antioxidants and corroborate previous associations of higher serum carotenoid levels with better cognition in aging subjects. There is emerging evidence that carotenoids, through their potent antioxidant and anti‐inflammatory properties, may positively impact cognitive function. Limiting cognitive decline through lifestyle, exercise, and a higher carotenoid intake, may prove beneficial.