Antioxidant supplements vitamin E and selenium -- taken alone or in combination -- did not prevent dementia in asymptomatic older men, according to a study published online by JAMA Neurology.

Antioxidants as potential treatment for cognitive impairment or dementia have been of interest for years because oxidative stress has been implicated as a dementia pathway.

The Prevention of Alzheimer's Disease by Vitamin E and Selenium (PREADViSE) clinical trial initially enrolled 7,540 older men who used the supplements for an average of about five years and a subset of 3,786 men who agreed to be observed longer. The men received either vitamin E, selenium, both or a placebo.

The incidence of dementia (325 of 7,338 men [4.4 percent]) was not different among the four study groups, according to the results in the article by Richard J. Kryscio, Ph.D., of the University of Kentucky, Lexington, and coauthors.

Limitations of the study include losing about half of the participants to long-term follow-up during the transition from a randomized clinical trial to a cohort study. Publicity about the negative effect of supplements also may have played a role, according to the authors.

"The supplemental use of vitamin E and selenium did not forestall dementia and are not recommended as preventive agents. This conclusion is tempered by the underpowered study, inclusion of only men, a short supplement exposure time, dosage considerations and methodologic limitations in relying on real-world reporting of incident cases," the article concludes.

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Primary Resource:

Kryscio, R. J., Abner, E. L., Caban-Holt, A., Lovell, M., Goodman, P., Darke, A. K., ... & Schmitt, F. A. (2017). Association of antioxidant supplement use and dementia in the Prevention of Alzheimer’s Disease by Vitamin E and Selenium trial (PREADViSE). JAMA neurology. DOI: 10.1001/jamaneurol.2016.5778