Consumption of Antioxidants and Its Long-Term Effect on Dementia Risk

This study was conducted to assess the risk of dementia over the years in people and its association with the amount of antioxidants they take in through their diet. A total of 5,395 participants were followed up for an average of about 10 years and it was seen that 465 of them developed dementia. Notably, 365 of them were diagnosed with Alzheimer’s disease. High intake of vitamin E – a known antioxidant in the diet – was associated with a lower risk of dementia and related conditions.

Dementia and other age-related memory and cognitive disorders like Alzheimer’s disease are said to have a pathological basis in oxidative injury and oxidative stress. Some studies have thus speculated that agents that can fight oxidative injury, such as antioxidants, might therefore help in protecting against such degeneration of the brain. So far, Alzheimer’s disease studies on humans have shown no benefit of antioxidants in treating the condition. However, a few studies have shown the protective benefits of these agents in dementia when used over the years, before the onset of the condition. This study looked at a large population of people who were followed up for almost a decade to determine the protective effects of vitamins E, C, flavonoids, and beta carotene.

* The study involved 5,395 participants from the general population, aged over 55 years. The participants were assessed at the beginning of the study to check for the absence of dementia.
* Regular assessments for dementia were done during the follow-up checkups, by using standard screening examinations and neuroimaging data, in addition to evaluation by a neurologist and a neuropsychologist, where required.
* All the participants were expected to send in complete dietary information during the study period.
* At the end of the study, the total consumption of vitamins E, C, flavonoids, and beta carotene in the individuals was calculated. At the end of the study, the number of patients with dementia and Alzheimer’s among the population was also computed. A correlation was sought between the two to determine the protective effects of the antioxidants.

Key findings
* On following up the participants for nearly 10 years, the researchers noted that 465 developed dementia and 365 participants among these developed Alzheimer’s disease.
* The participants who belonged to the upper 25 percent group in terms of amount of vitamin E intake were 25 percent less likely to get dementia. This result was assessed after considering other factors that raise the risk of dementia, such as increased age, educational status, alcohol and smoking habits, obesity, and use of supplements.
* Vitamin C, flavonoids, and beta carotene were found not to be associated with the risk of dementia.
* The results remained similar while specifically looking at Alzheimer’s disease.

Next steps/shortcomings
The authors acknowledge that the study relied on the reports of the participants, who might have changed their dietary habits after enrolling in the study. This could have changed the results. They agree that since this study involved only observing the participants and not intervention with supplements, the results could have been influenced by other factors. They recommend further studies that would directly supplement participants over several years with the antioxidant and examine the protective effects on dementia incidence.

This unique study shows that vitamin E intake moderately protects against the onset of dementia in a large population followed up over a decade. It also estimates the incidence of dementia in a general population over a decade. This study also determines the adequacy (or lack of) of vitamin E in the Western diet, as opposed to looking at populations that have been given vitamin E supplements in many similar, smaller clinical trials. The authors recommend future research that looks at diet-based antioxidants and the risk of dementia at different points in an individual’s life. For example, this study focused on older adults. Future studies may look at modulation of dementia risk by antioxidants at different time points in life.

For More Information:
Dietary Antioxidants and Long-Term Risk of Dementia
Publication Journal: Archives of Neurology, July 2010
By Elizabeth E. Devore; Francine Grodstein; Harvard School of Public Health and Harvard Medical School, Boston, Massachusetts

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