For people confronted with the mental decline of a loved one, the idea that taking vitamin E every day appears to slow down the progression of Alzheimer's disease is welcome news.

The study followed people with mild to moderate Alzheimer's disease (AD) for two years. Progression of AD slowed by about 19% in those who took 2000 IU (International Units) of vitamin E every day.

Only the people taking vitamin E showed a significant slowing of Alzheimer's progression.

The researchers estimate that this meant a patient's decline slowed down by more than six months during the course of the study, and that those taking vitamin E needed, on average, two hours less caregiver time per day.

All the patients were also taking an acetylcholinesterase inhibitor, a standard medication for Alzheimer's disease.

Patients were assigned to one of four groups in the double-blind, randomized trial: One group received 2,000 IU of vitamin E daily; another 20 milligrams/day of the drug memantine; a third received both vitamin E and memantine; and a fourth a Placebo. All four groups were followed for about two years.

Only the people taking vitamin E showed a significant slowing of Alzheimer's progression.

Memantine is a drug approved by the U.S. Food and Drug Administration for treatment of moderate to severe Alzheimer's. It is often prescribed off-label to patients with mild to moderate Alzheimer's, though its effectiveness has not yet been proved.

Patients' health was measured by their score on the Alzheimer’s Disease Cooperative Study/Activities of Daily Living Inventory (ADCS-ADL), a questionnaire that measures a person's ability to perform many of the tasks of daily life. A higher score means better performance on the 23-question, 78-point questionnaire.

Over the course of the study, everyone's ADCS-ADL scores dropped. But the scores of people in the vitamin E group dropped less — over three points less — than the scores of people who took placebo and slightly more than one point less than those taking memantine group (1.98) or vitamin E plus memantine (1.76), results which suggests that taking memantine blunts the positive effect of vitamin E.

As the researchers point out, for an Alzheimer's patient, an ADCS-ADL score that is 3.15 points higher could mean a major difference in the quality of their daily life, such as preventing the person from becoming unable to dress or bathe independently.

The study appears in JAMA, The Journal of the American Medical Association.