By Gene Emery
An extensive review of research on exercise, nutritional supplements, drugs and brain-training techniques concludes there is no definitive evidence that any of them protect against Alzheimer's disease or other types of dementia.
"To put it simply, all evidence indicates that there is no magic bullet," said Dr. Eric B. Larson, executive director of the Kaiser Permanente Washington Health Research Institute in Seattle, in an editorial online December 18 in the Annals of Internal Medicine, where the analyses appear.
The results are important because as the population gets older, the number of people with dementia increases. However, in some regions such as the United States, Canada and the United Kingdom, the odds of developing dementia seem to be declining. The reasons are not clear.
The analysis of studies looking at the effects of nutritional supplements found that those like ginkgo biloba, folic acid, multivitamins, vitamin D, vitamin E and beta carotene "did not reduce the risk for cognitive decline."
A second analysis reviewing tests of diabetes medications, hormones, lipid-lowering medicines, dementia medicines and anti-inflammatory drugs found that they "neither improved nor slowed decline in cognitive test performance" while sometimes posing a risk of side effects.
A third analysis concluded that tests of brain-training programs, sometimes marketed to normal people or people with mild cognitive impairment, revealed the training might help improve specific skills but produced no real broad improvement in brain functioning.
"If you exercise one of those functions, that function will improve but other areas may not change all," said Dr. Paul Schulz, a dementia neurologist at the University of Texas Health Science Center in Houston. "So if you exercise attention, that may not improve your ability to find the grocery store."
The same lack of evidence was seen when assessing the ability of physical activity to slow the development of dementia in adults who have not been diagnosed with cognitive impairment. The studies included evaluations of things such as aerobic training, resistance training and tai chi.
When it comes to the idea that exercise might delay brain deterioration, "we're not very good at actually studying physical activity," Dr. Rhonda Au, a professor of anatomy and neurobiology, neurology and epidemiology at the Boston University School of Medicine told Reuters Health by phone.
"I think it's a little bit unrealistic to think that in a short period of time for something as complex as Alzheimer's disease or dementia that we're going to see real effects," said Au, who was not involved in the reviews. "The overall take-home message is we're not doing a very good job of studying it in a very systematic way."
With nutritional supplements, evidence is limited because "very few have been thoroughly studied," said Schulz, who also was not involved in the reviews. There's also concern that "we don't know if they interfere with the medications that we do give people that we know helps them."
In a phone interview, he cited the case of a patient who was taking 20 supplements for memory "and he was really confused. We just stopped all 20 and he got a lot better. If you put 20 things in a blender, you don't know what's going to come out the other side."
Schulz and others said there is a strong sense among researchers that they are closing in on treatments that will be effective at stalling dementia.
Dean Hartley, director of science initiatives for the Alzheimer's Association, noted that other groups that have looked at the evidence have offered a more upbeat conclusions than the current studies.
For example, a review published in July in The Lancet estimated that among all the causes of dementia, about one third of them might be modified by a person's lifestyle. That group calculated that getting a good education cuts the risk by 8%. In midlife, preventing or correcting hearing loss reduces the risk by 9%, treating high blood pressure cuts it by 2% and not being obese lowers it by 1%. Late in life, the risk goes up 5% among smokers, 4% for people with depression, 3% for folks who are physically inactive, 2% for those experiencing social isolation and 1% if they have diabetes.
"I'm optimistic about this," Hartley told Reuters Health in a telephone interview. The authors of the new analyses "didn't come to the point to say this specifically would change the course of cognitive decline or dementia. But solid evidence is starting to mount to suggest that lifestyle can have an impact."
"When people ask me how to prevent dementia, they often want a simple answer, such as vitamins, dietary supplements, or the latest hyped idea," Larson writes in the editorial.
They can take many commonsense actions that promote health throughout life and may help to avoid or delay (Alzheimer's and other dementias), namely regular physical activity; control of vascular risk factors, including preventing or effectively managing diabetes; not smoking; and maintaining a healthy diet and weight, he writes.
"Engaging in cognitively stimulating activities and avoiding social isolation also are probably beneficial," Larson continues. So is correcting vision and hearing loss in the elderly, along with avoiding long-term use of certain drugs.
"There are things people can do now that will do no harm," Hartley said. "Most of these things will benefit your general health."
SOURCES: http://bit.ly/2BIYmOg, http://bit.ly/2CZ88K2, http://bit.ly/2Bvliy3, http://bit.ly/2B9afgZ and http://bit.ly/2CAp5cr
Ann Intern Med 2017.
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