Antioxidant defences and oxidative stress markers in erythrocytes and plasma from normally nourished elderly Alzheimer patients

Objectives: to investigate blood markers of oxidative stress, and enzymatic and non‐enzymatic antioxidants in normally nourished elderly people with Alzheimer's disease. Design: case–control study. Subjects: twenty patients with Alzheimer's disease and 23 elderly control subjects, living at home, free from disease and not undergoing any treatment known to have a strong influence on blood oxidative stress markers or antioxidant defence systems. Methods: we performed a nutritional evaluation, including anthropometric and biological measures and a 3‐day dietary record. We determined concentrations of antioxidant vitamins (α‐tocopherol, retinol) and malondialdehyde in plasma and erythrocytes. We also measured erythrocyte enzymatic activities of glutathione peroxidase and copper–zinc superoxide dismutase. Results: the two groups were similar in age, body mass index, dietary record and serum albumin concentration. After adjustment for age, sex and cardiovascular co‐morbidity, mean plasma concentration of α‐tocopherol was lower in those with Alzheimer disease than in control subjects (15±3.5 mg/l compared with 18.2±3.5; P=0.002), as was the mean plasma concentration of retinol (0.54±0.2 mg/l vs 0.7±0.2; P=0.014). The mean concentration of free plasma malondialdehyde was higher in those with Alzheimer's disease (0.70±0.2 mmol/l vs 0.5±0.1; P=0.036). In Alzheimer disease patients, free plasma malondialdehyde concentrations were inversely correlated with levels of α‐tocopherol (P=0.002) and retinol (P=0.025). Erythrocyte levels of vitamins and enzymatic activities were similar in the two groups. Conclusion: lower plasma concentrations of α‐tocopherol and retinol in normally nourished elderly patients with Alzheimer's disease than in controls could suggest that these antioxidant vitamins had been consumed as a result of excessive production of free radicals.