A major new review of published studies on interventions for the prevention of Alzheimer’s disease and other late-life dementias has found no good evidence that any of them work.
The four interventions include various types of physical activity, cognitive (“brain”) training, prescription medications and over-the-counter vitamins and supplements.
That may sound disheartening, but only if you’re pinning your hopes on a specific dementia intervention, like doing a crossword puzzle or downing an omega-3 supplement each day. Butler said she and her colleagues did find some potentially positive findings within the research they reviewed — ones that are consistent with familiar public health messages about healthy aging.
“It’s the same message about taking care of yourself,” she said. “Do what you can that is under your control: Eat a good diet, be physically active and stay cognitively involved.”
The review was conducted by the EPC, which is a collaborative venture between the University of Minnesota and the Minneapolis VA Health Care System, at the request of the National Institute of Aging. It was published Tuesday as a series of articles in the Annals of Internal Medicine.
No easy answer
For the review, Butler and her colleagues primarily focused on randomized clinical trials, considered the gold standard of research. Here are the review’s general findings regarding each type of intervention:
- Cognitive training. The researchers reviewed 11 clinical trials that involved adults with either normal or mildly impaired cognition. “We saw improvements in the [cognitive] areas that people trained in, but there was not enough evidence for us to say that the improvement generalizes across the brain,” said Butler. When the training involved improving the brain’s processing speed, for example, there was no improvement in memory.
- Prescription medications. After examining the data from 51 clinical trials, the researchers concluded that no medications appeared to prevent or delay cognitive decline or dementia. This included drugs aimed specifically at treating dementia, as well as drugs used to treat other age-related health problems, such as high blood pressure, diabetes and falling hormone levels. Drugs containing the hormones estrogen and estrogen-progestin (sometimes prescribed to postmenopausal women) were linked with an increased risk of dementia, the researchers found. “There are some signs that hypertension medications might work, but it’s slim,” said Butler.
- Vitamins and supplements. The researchers analyzed the results of 38 clinical trials that looked at whether various vitamins and supplements could prevent or delay cognitive decline or dementia. None was found to have such an effect. Among the interventions tested in the trials were omega-3 fatty acids, soy, ginkgo biloba and vitamins B, C, D and E, as well as various multivitamin combinations.
- Physical activity. In reviewing the data on physical activity and dementia, Butler and her colleagues looked at 16 clinical trials that compared various forms of physical activity interventions — aerobic exercise, resistance training and tai chi — with non-active controls. They found no strong evidence that any single type of exercise prevented cognitive decline, although some studies suggested that doing aerobic and/or resistance training might have positive effects. The problem with many of the existing studies on exercise, said Butler, is that the participants were followed for a relatively short period of time.
One well-designed study, known as FINGER (Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability), did see cognitive improvement among a group of adults aged 60 to 77 considered at high risk for dementia who received an intervention that combined physical activity with dietary changes and cognitive training.
“Because there is a lot that we don’t understand about the mechanisms of dementia, it’s probable that there are many things that contribute to the development of dementia, so it shouldn’t be at all surprising to us that it may take more than one thing to delay or prevent it,” said Butler.
“When people ask me how to prevent dementia, they often want a simple answer, such as vitamins, dietary supplements, or the latest hyped idea,” writes Dr. Eric B. Larson, an internist and executive director of the Kaiser Permanente Washington Health Research Institute, in a commentary that accompanies the review. “I tell them that they can take many commonsense actions that promote health throughout life and may help to avoid or delay” Alzheimer’s disease and related dementias.
Those actions include engaging in regular physical activity, not smoking, maintaining a healthy diet and weight, and controlling high blood pressure and diabetes.
“Engaging in cognitively stimulating activities and avoiding social isolation also are probably beneficial,” he says.
In addition, Larson urges doctors to help older patients correct their vision and hearing loss.
“Note that none of these recommendations has harmful side effects,” he adds.
FMI: You can find abstracts of the four review articles and the editorial on the Annals of Internal Medicine website, but the full articles are behind a paywall.