Thursday, June 22, 2017

Encouraging, but inconclusive evidence on interventions to prevent cognitive decline, dementia

The public is enormously concerned about dementia and cognitive impairment, and a wide range of programs and products, such as diets, exercise regimens, games, and supplements, purport to keep these conditions at bay. It is difficult for individuals, health care providers and policy makers to ascertain what has been demonstrated to prevent or reduce risk.

To help sort through the data and to understand the quality and weight of current evidence for possible interventions, the National Institute on Aging (NIA) at the National Institutes of Health, commissioned experts for an extensive scientific review and to provide recommendations for public health messaging and future research priorities. In response to that request, a National Academies of Sciences, Engineering and Medicine (NASEM) committee has concluded that current evidence does not support a mass public education campaign to encourage people to adopt specific interventions to prevent cognitive decline or dementia.

Importantly, the committee also cited “encouraging although inconclusive” evidence for three specific types of interventions — cognitive training, blood pressure control for people with hypertension, and increased physical activity. Based on that evidence, the committee recommended providing the public with accurate information about their potential positive impacts for some conditions while more definitive research on these and other approaches moves forward. The committee suggested that health care providers might include mention of the potential cognitive benefits of these interventions when promoting their adoption for the prevention or control of other diseases and conditions.

The full NASEM report, “Preventing Cognitive Decline and Dementia: A Way Forward,” can be viewed at (link is external).

The committee’s recommendations are based in large part on an NIA-requested and supported systematic evidence review by the Agency for Healthcare Research and Quality’s (AHRQ) Evidence-based Practice Center (EPC). The Minnesota EPC categorized hundreds of studies by strength and quality for the AHRQ part of the project.

“We’re all urgently seeking ways to prevent dementia and cognitive decline with age,” said NIA Director Richard J. Hodes, M.D. “But we must consider the strength of evidence -- or lack thereof -- in making decisions about personal and public investments in prevention. I am grateful for the National Academies’ and AHRQ’s careful reviews, which recognize the progress research has made in beginning to answer such questions, while pointing the way for additional studies. This report will be very instructive for what we can tell the public now, as critical research continues.”

The committee noted potential effects, as well as limitations of the evidence, for:

Cognitive training 

Interventions aimed at enhancing reasoning, memory, and speed of processing, to delay or slow age-related cognitive decline were found promising, based primarily on conclusions from the NIA-funded Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) trial and bolstered by additional data from prospective observational studies on the benefits of cognitively stimulating activities.

The committee cautioned, however, that it could not draw conclusions about the relative effectiveness of different cognitive training approaches or techniques. It also noted that there was no evidence to support the notion that beneficial long-term cognitive effects suggested by the ACTIVE trial could be applied to computer based brain training applications being offered commercially, as the suite of cognitive interventions in the ACTIVE trial were substantially different.

The committee found no evidence to suggest that cognitive training might prevent, delay or slow development of Mild Cognitive Impairment (MCI) or Alzheimer’s, however.

Blood pressure management for people with hypertension 

Encouraging but inconclusive evidence suggests that blood pressure management, particularly in midlife, might prevent, delay or slow clinical Alzheimer’s-type dementia, according to the committee. While clinical trials in this area do not offer strong support for blood pressure management against Alzheimer’s, prospective population studies and what we have learned about the natural history and biology of the disease make it plausible, then, that blood pressure management for people with hypertension would also reduce their risk of dementia and cognitive decline, the report said.

The committee pointed out the known cardiovascular benefits from well-managed blood pressure, which would be experienced while Alzheimer’s prevention is potentially addressed.

Increased physical activity 

Citing the many known health benefits of physical activity, the committee pointed to growing evidence that among these is the possible reduced risk of age-related cognitive decline. Here, too, the experts turned to what they called encouraging but inconclusive evidence, noting that clinical trials results in this area suggest effectiveness, taken together with observational studies and knowledge of neurobiological processes. There was not sufficient evidence to support increased physical activity as a preventive intervention for MCI or Alzheimer’s disease, however. Further, the committee could not find sufficient evidence to help determine which specific types of physical activity might be particularly effective for preventing cognitive decline and dementia.

In communicating with the public, the committee said, the NIH, the Centers for Disease Control and Prevention and other organizations should present potential benefits of the three interventions as they apply to cognitive decline, MCI, and Alzheimer’s dementia, while pointing out the limitations of the evidence. There are considerable challenges in presenting such nuanced messages, it added, as the public likely will not draw fine distinctions among the three conditions or about levels of evidence.

The committee expressed optimism for the future of research to provide answers that the public and providers are seeking. Substantial knowledge has been gained since the last comprehensive evidence review in 2010, and this complex and exciting area of discovery will continue to grow with investments in research. In addition to encouraging ongoing research in the three areas for which it found evidence most developed, the committee recommended as priority areas for further study: new anti-dementia treatments; treatments for diabetes and depression; dietary interventions; lipid-lowering treatments; sleep quality interventions; social engagement, and vitamin B12 plus folic acid supplementation.

For its evidence review, the AHRQ’s EPC examined the scientific literature on 13 classes of interventions associated with preventing, slowing, or delaying the onset of clinical Alzheimer’s-type dementia and MCI. The AHRQ report, issued in March 2017, found that most approaches showed no evidence of benefit to delay or prevent age-related cognitive decline, MCI, or Alzheimer’s dementia. It concluded that, at present, there is not sufficient strength of evidence to justify large-scale investing in public health activities aimed at preventing dementia; some results may be viewed as potential added benefits to already identified public health interventions.

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