A major new study offers discouraging news about dementia: Nothing is yet proven to prevent cognitive decline late in life.
Despite marketing claims for “brain diets,” “brain games” and other interventions, a thorough analysis of all published research shows that diet, drugs, cognitive training, exercise, vitamins or supplements do not prevent Alzheimer’s disease or related types of dementia in people older than 85.
“There’s no magic bullet,” said Dr. Mary Butler, co-director of the Minnesota Evidence-based Practice Center, which conducted the analysis and guides federal policy recommendations. The research, funded by the U.S. Agency for Healthcare Research & Quality, is published in Monday’s issue of the Annals of Internal Medicine.
There is an urgent need to prevent the brain disease that causes loss of memory, thinking and judgment. The number of Americans with either mild cognitive impairment or Alzheimer’s disease is expected to double by 2060 to 15 million, up from approximately 6.1 million this year.
Because there are no cures or even treatments to change progression of the disease, hopes have been pinned on prevention. Even delaying its onset would profoundly help, wrote Dr. Eric B. Larson of the Kaiser Permanente Washington Health Research Institute in Seattle, in an accompanying editorial.
The team analyzed the published evidence of 13 different types of interventions.
“We looked at drugs. We looked at over-the-counter vitamins and supplements. We looked at exercise. We looked at cognitive training. And overall, the results didn’t show much benefit,” said Dr. Howard Fink of the Minneapolis VA Health Care System.
A small minority of study results suggested potential benefits of a few small interventions.
For instance, when the researchers looked at the evidence for “cognitive training,” they found that people improved in the areas that they trained in — but did not improve in other areas. So while training may boost the time it takes for you to perform a mental task, that same training won’t help memory and other mental functions.
The only interventions that seemed promising are already goals of standard medical care, such as regular physical activity, controlled blood pressure, healthy weight, quitting smoking and treating diabetes and other vascular risk factors.
“When people ask me how to prevent dementia, they often want a simple answer, such as vitamins, dietary supplements or the latest hyped idea,” wrote Larson.
“I tell them that they can take many common-sense actions that promote health throughout life.”
The reasons why these more hyped interventions fail aren’t entirely clear.
Perhaps the interventions were too short, or started too late in life. To prevent dementia, interventions may need to start when people are far younger, and continue for years. But such a lengthy study would be very expensive and pose major logistical challenges, said Butler.
Or maybe they just don’t work.
“It’s a humbling result,” said Fink. “It tells us that we have a lot to learn.”
What researchers found about fighting dementia
- Physical exercise. Researchers reviewed data from 16 trials comparing a physical activity intervention with an inactive control. They found insufficient evidence to draw conclusions about the effectiveness of aerobic training, resistance training, or tai chi for improving cognition. The researchers did find low-strength evidence that combining different types of interventions at the same time, such as physical activity, diet, and cognitive training, improved cognitive test performance.
- Prescription Medications. Researchers reviewed data from 51 trials comparing the effect of prescription medication with placebo, usual care, or active control on cognitive outcomes. The evidence did not support use of any of the studied pharmacologic treatments (dementia medications, antihypertensives, diabetes medications, NSAIDs or aspirin, hormones, and lipid-lowering agents) for cognitive protection in persons with normal cognition or mild cognitive impairment.
- Cognitive Training. A review of 11 trials of adults with either normal cognition or mild cognitive impairment at the time of enrollment found insufficient evidence that cognitive training exercises could prevent dementia. Group cognitive training was found to improve performance only in the cognitive domain trained. For example, memory training improved memory, but did not improve any other aspects of cognition.
- Over-the-counter vitamins and supplements. The study authors reviewed 38 trials comparing over-the-counter (OTC) supplements, including omega-3 fatty acids, soy, ginkgo biloba, B vitamins, vitamin D plus calcium, vitamin C or beta carotene, multi-ingredient supplements, with placebo or other OTC interventions for preventing or delaying cognitive decline, mild cognitive impairment, or clinical Alzheimer-type dementia. They found insufficient evidence to suggest that any of the supplements worked to reduce the risk for cognitive decline.
Source: Annals of Internal Medicine