Study finds evidence on preventive interventions for cognitive decline and dementia

A new report published by the National Academies of Sciences, Engineering, and Medicine shows evidence supporting three interventions for cognitive decline and dementia—cognitive training, blood pressure management for people with hypertension, and increased physical activity, which might slow down cognitive decline and the onset of dementia.

The study is encouraging in showing modest evidence in preventing cognitive decline and dementia, which however is not sufficient in justifying a public health campaign to focus on adopting them.

There is good cause for hope that in the next several years much more will be known about how to prevent cognitive decline and dementia, as more clinical trial results become available and more evidence emerges,"

"Even though clinical trials have not conclusively supported the three interventions discussed in our report, the evidence is strong enough to suggest the public should at least have access to these results to help inform their decisions about how they can invest their time and resources to maintain brain health with aging."

Alan I. Leshner, chair of the committee and CEO emeritus, American Association for the Advancement of Science.

The Agency for Healthcare Research and Quality (AHRQ) and an associated "state of the science" conference at the National Institutes of Health published a systematic review earlier in 2010. They concluded that the evidence was not sufficient to recommend any interventions for the prevention of cognitive decline and dementia.

Ever since, there have been significant advances to understand the pathological processes that resulted in dementia; numerous clinical trials have been completed and published for potential interventions in prevention.

The National Institute on Aging (NIA) contracted with AHRQ in 2015 to conduct another systematic review of the current evidence. NIA also asked the National Academies to assemble an expert committee to help in informing the design of the AHRQ review and then make use of the outcomes to provide suggestions in informing the development of public health messaging and to offer recommendations for future research.

This report inspected the most recent evidence on steps that could be considered in 1) prevention, slow down, or delaying the onset of mild cognitive impairment and clinical Alzheimer's-type dementia and 2) delaying or slow down of cognitive decline related to age.

In spite of an array of advances available to understand cognitive decline and dementia, the committee determined the available evidence, considered to be the gold standard of evidence that are derived from randomized controlled trials, remains comparatively limited and has significant shortcomings.

Based on the completeness of the evidence available, three types of intervention activities are mentioned by the committee that could delay or slow down the cognitive decline related to age. They are:

1. Structured cognitive training programs that are computer based or non-computer based, that are aimed to enhance reasoning, problem solving, memory, and speed of processing
2. blood pressure management for people with hypertension (for clinical Alzheimer's-type dementia)
3. increased physical activity.

However the committee concluded by describing these three types of interventions as supportive and encouraging but the evidence is not convincing.

In the past 15 years, cognitive training is a subject matter of significant interest and debate in both the academic and commercial sectors. While there is enough evidence that shows the short term benefits of cognitive training in improving performance on a trained task, the center point for the debate is on the evidence for long-term benefits and whether training in a domain will yield benefits to others.

For example, will training on a task that improves processing speed help to improve memory and reasoning? And, can this be translated to maintain independence in important daily activities such as driving and remembering to take medications?

While evidence from one randomized controlled trial suggests this possibility when cognitive training is delivered over time and in an interactive context, mixed results are obtained from other randomized controlled trials that are tested for cognitive training.

The report said the available evidence in combination with strong evidence for blood pressure management to prevent stroke and heart disease and the relative benefit/risk ratio of antihypertensive medications and lifestyle interventions, is adequate for justifying communication with the public regarding the use of blood pressure management during midlife (35—65 years) in particular.

However the committee mentioned that although the evidence is encouraging, the evidence for prevention, delay, and slowing down clinical Alzheimer's-type dementia is not convincing.

The health benefits of physical activity are well documented and some of these benefits include prevention of stroke that is casually related to the health of the brain. The AHRQ systematic review has found the randomized controlled trials to result in patterns across different physical activity interventions types.

They provide a sign of effectiveness of increased physical activity in postponing or slow down of cognitive decline related to age. Although these results were not consistently positive several other considerations have led the committee to conclude that the evidence is adequate to justify communicating to the public that the evidence of this intervention is encouraging but not convincing.

Based on the quality of randomized controlled trials and the lack of consistent positive results across independent studies none of the interventions assessed in the AHRQ systematic review met the criteria for being supported by high-strength evidence. The committee that carried out the study mentioned in their written report that additional research is required for further understanding and to gain confidence in the efficiency.

The study highlighted the need for methodological improvements in the future research and to strengthen the evidence based on cognitive training, blood pressure management, and increased physical activity.

Research priorities such as the effectiveness of different forms of cognitive training interventions can be compared and evaluated, finding whether optimal blood pressure targets are available and among different age groups, comparison of the effects of the different forms of physical activity are cited as examples for these three classes of interventions.

The committee said the National Institutes of Health and other organizations interested should support further research and in providing research funds for cognitive decline and dementia prevention that:

1. Should find higher risk individuals of cognitive decline and dementia.
2. The participation of the underrepresented populations can be increased.
3. Interventions can be started at a younger age and the follow-up periods can be made longer.
4. To enable pooling, consistent cognitive outcome measures can be used across trials and robust outcome measures can be integrated into trials with other main purposes.
5. Biomarkers can be included for intermediate outcomes.
6. To test the effectiveness of the intervention in broad, regular clinical practices or community settings large trials can be carried out.