Taking vitamin E during the early stages of Alzheimer's disease slowed declines in patients' ability to perform basic tasks by about six months in a new study.
"It will be very interesting to see to what extent this will change practice," Dr. Maurice Dysken said. "I think it will, but we'll have to see how people in the field such as providers view the findings and patients too."
Dysken is the study's lead author and former director of the Geriatric Research, Education and Clinical Center at the Minneapolis VA Healthcare System.
Researchers have studied vitamin E for possible benefits in slowing the progression of Alzheimer's, but those studies have yielded mixed results.
For example, the researchers write in JAMA, past research has found the vitamin slowed disease progression in people with moderately severe Alzheimer's. But the vitamin was not effective at slowing the transition to Alzheimer's for people with so-called mild cognitive impairment, which typically precedes Alzheimer's.
To see whether vitamin E - or a combination of the vitamin with memantine, a drug approved in the U.S. to treat Alzheimer's - would slow the rate of decline in people with mild to moderate forms of the disease, the researchers recruited 613 trial participants from 14 Veterans Affairs medical centers.
The patients were recruited between August 2007 and March 2012. People taking blood thinning drugs were excluded from the study because those drugs are tied to an increased risk of bleeding when combined with vitamin E.
At the start of the study, the participants were randomly assigned to one of four groups.
One group received 2,000 International Units (IU) of vitamin E every day. That's a considerably larger dose than the 30 IU typically found in multivitamins. A second group received the drug memantine. A third group took both vitamin E and memantine and the final group took inert pills for comparison.
The researchers used a scale to measure the participants' ability to perform tasks of daily life.
After an average of about 2.3 years, Dysken and his colleagues found that only the group taking vitamin E alone had a significantly slower decline in the ability to perform daily tasks, compared to the participants taking the inert pills.
The difference represented a delay in functional decline of about six months. In practical terms, the difference could represent a person's ability to dress or bathe themselves for that much longer.
People who took care of the study participants taking vitamin E alone also reported a smaller increase in the amount of time the patients needed assistance, compared to the other groups.
"I think it's a well done study, but I think the results are modest," Dr. Ronald Petersen, who was not involved in the new work, said.
Petersen is director of the Alzheimer's Disease Research Center at the Mayo Clinic in Rochester, Minnesota.
He noted that the benefits need to be weighed against potential risks - for example, a previous study showed an increased risk of death among people taking vitamin E. The current study didn't detect any such increase.
"Nevertheless, it's out there and it's published," he said. "You have to let people know it could be a small risk."
Both Petersen and Dysken cautioned that the study doesn't suggest people should take vitamin E to prevent or stop Alzheimer's disease.
"This is not a prevention trial," Dysken said. "We were enrolling patients with a diagnosis and what we're looking at is slowing the rate of progression. It does not stop it."
In an editorial accompanying the new study, Dr. Denis Evans of Rush University Medical Center in Chicago agreed that the results show a modest effect on treating symptoms of Alzheimer's.
"Considering the difficulties inherent in trying to treat rather than prevent very high-prevalence diseases and the limitations thus far of the therapeutic efforts for people with AD, shifting to more emphasis on prevention seems warranted," he wrote.
While a lot of research is being focused on prevention of the disease itself, rather than of its progression, Petersen said the new study shows researchers are not abandoning people who already have Alzheimer's.
"I think this is an example that we're really doing research across the entire spectrum of the disease," he said.
He added that the new findings will probably not cause him to treat patients differently, but he said it's something he would mention if they asked if there's anything else that can be done.
"I think a six-month delay will be meaningful for many - if not most - patients," Dysken said. "But it really does depend on the conversation that needs to be had between patient and primary care provider."