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2 Communicating with the Public about Interventions to Prevent Cognitive Decline and Dementia
Pages 37-76

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From page 37...
... To supplement the AHRQ systematic review, the committee considered evidence from relevant studies using other methodologies, including observational studies1 and neurobiological studies that support the biological plausibility of the effectiveness of a class of interventions; information from studies of risk factors; information about intervention effects on intermediate outcomes (e.g., changes in brain structure and function) that may predict cognitive decline and dementia; knowledge about whether and how an intervention would benefit or harm other organ systems; and information about other general harms and costs potentially associated with an intervention (see Chapter 1)
From page 38...
... In the committee's judgment, when the Bradford Hill criteria are applied to blood pressure management and physical activity, there is sufficient evidence from observational studies and neurobiological understanding to include these interventions in communications with the public. Given the moderate-strength RCT evidence for cognitive training, the committee did not apply the Bradford Hill criteria to this intervention domain.
From page 39...
... Cognitively stimulating activities, for the purposes of this report, include such interventions as learning a new language and increasing proficiency in daily activities, such as playing bridge and doing crossword puzzles. Cognitive training has engendered considerable interest and debate in both the academic and commercial sectors, particularly within the past 15 years (Simons et al., 2016)
From page 40...
...  AHRQ SYSTEMATIC REVIEW: BOX 2-1 SUMMARY OF FINDINGS ON COGNITIVE TRAINING INTERVENTIONS • Most studies addressed intermediate outcomesa of cognitive training in terms of cognitive performance and a few measures of brain activity. • The Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE)
From page 41...
... ACTIVE trial participants were random 3  Tables summarizing effect sizes for the impacts of the ACTIVE trial's cognitive training intervention on cognitive testing outcomes and IADLs (among other outcomes) at the 2-, 5-, and 10-year time points can be found in the 2017 AHRQ systematic review, Interventions to prevent age-related cognitive decline, mild cognitive impairment, and clinical Alzheimer's-type dementia (Kane et al., 2017)
From page 42...
... Specific training strategies for the three intervention arms (described in Box 2-2) differed, but the intervention conditions shared key features (Jobe et al., 2001)
From page 43...
... The ACTIVE trial was not designed to study the impact of cognitive training on the incidence of dementia, but an analysis conducted post hoc found no difference in incidence between intervention (all arms combined) and control arms4 (Unverzagt et al., 2012)
From page 44...
... The 5- to 10-year lag in training effects on functional outcomes observed in the ACTIVE trial underscores the importance of including long follow-up periods in study designs and highlights the challenge of research aimed at preventing cognitive decline and dementia. The ACTIVE trial represents a promising model for subsequent studies on cognitive training interventions but still suffered from notable methodological limitations that need to be considered in the discussion of its results.
From page 45...
... Future research on cognitive training interventions (discussed in Chapter 4) may help tease out the effects of different aspects of the ACTIVE intervention and address other questions that arise from the literature included in the AHRQ systematic review, such as the optimal duration of the intervention, the effects of differing levels of participation in cognitively stimulating activities at baseline, and whether training would be better than taking up other cognitively stimulating activities (e.g., reading, chess)
From page 46...
... to cognitive decline and dementia incidence. A recent systematic review found an association between lower educational attainment and worse cognitive outcomes in 18 of 27 prospective studies and 21 of 25 cross-sectional studies (Beydoun et al., 2014)
From page 47...
... BLOOD PRESSURE MANAGEMENT FOR PEOPLE WITH HYPERTENSION Lowering blood pressure in people with hypertension substantially reduces the risk of heart disease and stroke by slowing blood vessel changes that are the key causes of cardiovascular disease (Wang et al., 2005)
From page 48...
... , despite such efforts as those of the National High Blood Pressure Education Program to provide evidence-based guidance on blood pressure management to clinicians (NHLBI, 2004)
From page 49...
... A summary of the AHRQ findings on blood pressure management interventions is presented in Box 2-3. The AHRQ systematic review found inconsistent evidence from RCTs for an effect of blood pressure management on cognitive decline and dementia in patients with hypertension.
From page 50...
... . Although the AHRQ systematic review did not include a meta-analysis of these trials, prior meta-analyses including similar trial populations demonstrated a positive effect on cognitive outcomes with the use of antihypertensive treatment (Levi Marpillat et al., 2013; Peters et al., 2008)
From page 51...
... As the AHRQ systematic review notes, the limitations of the existing experimental evidence stem from the fact that few studies have been explicitly designed to measure the impact of blood pressure management on cognitive impairment and dementia. Instead, these trials typically were designed to measure the impact of antihypertensive treatment on cardiovascular outcomes, with cognitive outcomes being addressed in secondary analyses.
From page 52...
... Assessing Antihypertensive Treatment Against the Bradford Hill Criteria for Causation Although RCTs provide at best modest support for a role of blood pressure management in patients with hypertension for dementia prevention, other converging sources of evidence provide additional support. When assessed against the Bradford Hill criteria discussed earlier (Hill, 1965)
From page 53...
... While the experimental evidence on the effect on dementia incidence of blood pressure management in people with hypertension has varied, evidence from observational studies has shown a relatively consistent effect. In a recent systematic review, for example, 7 of 11 studies found that antihypertensive treatment was associated with reduced risk of dementia or Alzheimer's disease (Rouch et al., 2015)
From page 54...
... There are two converging arguments for the plausibility of blood pressure management reducing dementia incidence. First, blood pressure management in hypertensives may prevent dementia by preventing or delaying the progression of cerebrovascular disease.
From page 55...
... Other Known Health Benefits and Potential Harms and Costs In addition to the efficacy and observational data discussed above, two other considerations are relevant to communications with the public on the potential benefits of blood pressure management for prevention of cognitive decline and dementia. First, there is strong evidence indicating that effective blood pressure management substantially reduces the risk of fatal and nonfatal cardiovascular events and all-cause mortality in hypertensive patients (The SPRINT Research Group, 2015)
From page 56...
... . Given the underutilization of antihypertensive treatment for blood pressure management, broader diffusion of such treatments would likely have important societal benefits with respect to the incidence of cardiovascular disease.
From page 57...
... . Findings from the AHRQ Systematic Review Summary of the AHRQ Systematic Review Findings The AHRQ systematic review identified 43 RCTs of physical activity interventions, 19 of which were rated as having a low or medium risk of
From page 58...
... • While the majority of results showed no significant difference, the pat tern of results across very different types of physical activity interven tions provides an indication of effectiveness of physical activity. aThe AHRQ systematic review classified physical activity interventions as aerobic activity, resistance training, Tai Chi, or multicomponent physical activity.
From page 59...
... Although the AHRQ systematic review found that multicomponent physical activity interventions demonstrated no clear benefit for cognitive performance in adults with normal cognition, heterogeneity in the elements of multicomponent interventions limits the ability to generalize existing study results to all such interventions. Limitations of the AHRQ Systematic Review Findings The reasons for the mixed RCT data and the discrepancy between the results of RCTs and observational studies (discussed below)
From page 60...
... Assessing Physical Activity Against the Bradford Hill Criteria for Causation The pattern of positive results from RCTs included in the AHRQ systematic review provides an indication of short-term beneficial effects of physical activity, particularly in adults with MCI. However, physical activity interventions are not supported by sufficient evidence from clinical trials alone to justify public health messaging beyond the known physical benefits.
From page 61...
... FIGURE 2-1  Forest plots showing the association between high physical activity and cognitive decline based on a meta-analysis of observational studies. SOURCE: Blondell et al., 2014.
From page 62...
... A recent systematic review found that 6 of 8 observational studies reported significant negative associations between sedentary behavior and cognitive function (Falck et al., 2016)
From page 63...
... , reduction of inflammation, and reduction of brain beta-amyloid deposition. Indirectly, physical activity may prevent cognitive decline and dementia by reducing atherosclerosis and the associated risk of vascular disease (including stroke)
From page 64...
... Overall Summary When assessed against the Bradford Hill criteria, the existing body of evidence from observational studies lends some support, but is not conclusive, for a causal relationship between physical activity and cognitive decline and dementia. While many of the studies included in this analysis tried to adjust for confounding and assessed physical activity using standardized measures (Blondell et al., 2014)
From page 65...
... are causally related to brain health. There is growing evidence that among these health benefits is reduced risk of cognitive decline.
From page 66...
... Recommendation 1: Communicating with the Public When communicating with the public about what is currently known, the National Institutes of Health, the Centers for Disease Control and Prevention, and other interested organizations should make clear that positive effects of the following classes of interven tions are supported by encouraging although inconclusive evidence: • cognitive training -- a broad set of interventions, such as those aimed at enhancing reasoning, memory, and speed of processing -- to delay or slow age-related cognitive decline • blood pressure management for people with hypertension to prevent, delay, or slow clinical Alzheimer's-type dementia • increased physical activity to delay or slow age-related cogni tive decline
From page 67...
... 2002. Effects of cognitive training interventions with older adults: A randomized controlled trial.
From page 68...
... 2016. Effect of antihypertensive treatment at different blood pressure levels in patients with diabetes mellitus: Systematic review and meta-analyses.
From page 69...
... 2007. Left ventricular mass, blood pressure, and low ered cognitive performance in the Framingham offspring.
From page 70...
... 2017. Interventions to prevent age-related cognitive decline, mild cognitive impairment, and clinical Alzheimer's-type dementia.
From page 71...
... 2009. Use of blood pressure lowering drugs in the prevention of cardiovascular disease: Meta-analysis of 147 randomised trials in the con text of expectations from prospective epidemiological studies.
From page 72...
... 2010. Chronic endurance exercise training prevents aging-related cognitive decline in healthy older adults: A randomized controlled trial.
From page 73...
... 2005. The age-dependent relation of blood pressure to cognitive function and dementia.
From page 74...
... 2012. Ef fect of antihypertensive therapy on incident stroke in cohorts with prehypertensive blood pressure levels: A meta-analysis of randomized controlled trials.
From page 75...
... 2003. Effects of blood pressure lowering with perindopril and indapamide therapy on dementia and cognitive decline in patients with cerebrovascular disease.
From page 76...
... 2016. Aerobic exercise ameliorates cog nitive function in older adults with mild cognitive impairment: A systematic review and meta-analysis of randomised controlled trials.


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