Cognitive impairment and oxidative stress in the elderly: results of epidemiological studies

Cognitive impairment is a major component of age-related dementing diseases and it has been suggested that it could share the same pathological pathways with neurodegenerative processes and cerebrovascular lesions. The free radical theory of ageing could be one of these pathways. Implication of free radical damage in processes related to cerebral ageing is a good argument in favour of the hypothesis that antioxidants may protect against cognitive impairment. Observational studies (mostly cross-sectional) of relationships between cognitive impairment and antioxidant status are based on the evaluation of dietary intake or on the levels of carotenoids, selenium and vitamins A, C and E in plasma or red blood cells. More convincing results were obtained on vitamin C and carotenoids. Despite some limitations, the comparison between results obtained in various populations is becoming increasingly informative and these studies argue for a protective effect of antioxidants on cognitive performance.