The new research suggests that vitamin E and selenium supplements, taken alone or in combination, did not prevent or delay dementia in older men who are not showing any symptoms.
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 clinical trial initially enrolled 7,540 older men who used the supplements for an average of about five years and a subset of 3,800 men who agreed to be observed longer.
The men received either vitamin E, selenium, both or a placebo, but the study did not look at women.
The incidence of dementia was not different among the study groups, according to Dr Richard Kryscio, of the University of Kentucky, Lexington, who led the study.
The authors pointed out that there were limitations to the study as they lost about half of the participants to long-term follow-up.
This was because of a transition from a randomised clinical trial to a cohort study, but it appears the pills did not work.
Publicity about the negative effect of supplements also may have played a role, according to the authors.
Dr Kryscio added: “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 data was published online today by JAMA Neurology.