Four Clinical Trials Further Clarify The Role Of Physical Activity In Cognitive Function And Dementia
Four studies reported today at the Alzheimer's Association International Conference 2012 (AAIC 2012) describe the ability of targeted exercise training to promote improved mental functioning and reduced risk for cognitive impairment and dementia in cognitively healthy older adults and those with mild cognitive impairment (MCI).
The reports, from six- and 12-month randomized controlled clinical trials, depict the beneficial effects of different types of exercise – resistance training, aerobic training, and balance-stretching training – on a variety of cognitive abilities, brain structure, functional neural plasticity, growth factors, and risk factors for cognitive decline such as depression and sleep quality.
"Currently, the strongest data for lifestyle-based Alzheimer's risk reduction is for physical activity, yet this data is generally observational and considered preliminary, said William Thies, PhD, Alzheimer's Association Chief Medical and Scientific Officer. "These new intervention studies are taking place over longer periods of time to begin to clarify exactly which types of physical activity are most effective, how much needs to be done, and for how long. In particular, where previously we had seen positive associations between aerobic activity, particularly walking, and cognitive health, these latest studies show that resistance training is emerging as particularly valuable for older adults."
It is generally accepted that regular physical activity is essential to healthy aging; it also may prove to be a strategy to delay or prevent the onset of cognitive impairment and dementia.
"It is very important to learn more about factors that actually raise and lower risk for cognitive decline and Alzheimer's. To do that, we need long-term studies in large, diverse populations, and we need the research funding to conduct those trials. For example, we have learned very practical lifestyle risk factors for heart disease from long-term research like the Framingham Study. Alzheimer's now needs its version of that research," Thies added.
"By midcentury, care for people with Alzheimer's will cost the US over $1 trillion. This will be an enormous and unsustainable strain on the healthcare system, families, and federal and state budgets. The first-ever US National Plan to Address Alzheimer's was unveiled in May, and now this plan must be speedily and effectively implemented. An additional $100 million is needed now for Alzheimer's research, education, outreach and community support," Thies said.
Moderate walking may grow brain region related to memory; increase nerve growth factor
According to Kirk Erickson, PhD, of the University of Pittsburgh, "There is growing interest in lifestyle factors and interventions that enhance the cognitive vitality of older adults and reduce the risk for cognitive impairment. However, very little is understood regarding the molecular processes that contribute to enhanced brain health with exercise, or the impact that greater brain volume has on cognitive function."
Erickson and colleagues randomized 120 older adults without dementia who have been sedentary for the previous six months to a moderate intensity walking group or a stretching-toning group for one year. MRI was used to measure the size of a brain region associated with memory, known as the hippocampus, both before and after the exercise intervention. Blood was drawn to measure concentrations of brain-derived neurotrophic factor (BDNF), and a cognitive testing battery was conducted before and after the intervention.
The researchers found that, in this study group, one year of exercise training increased the size of the hippocampus by two percent (2 percent) in the walking group compared to the stretching-toning group. (Significant shrinking of the hippocampus is characteristic of Alzheimer's disease.) The increase in hippocampal volume was correlated with similar changes in BDNF.
"Our findings suggest that the aging brain remains modifiable, and that sedentary older adults can benefit from starting a moderate walking regimen," Erickson said.
Resistance training may improve thinking and memory in older adults with MCI
Exercise and regular physical activity may prove to be promising intervention strategies to postpone or prevent Alzheimer's dementia, but perhaps not all types of training are equally effective.
PhD student Lindsay Nagamatsu, of University of British Columbia, Vancouver, Canada, and colleagues with the EXCEL (EXercise for Cognition and Everyday Living) study compared the effects of both twice-weekly resistance training (weight lifting) (n=28) and twice-weekly aerobic training (walking) (n=30) with twice-weekly balance and tone exercises (n=28) on executive cognitive function in women aged 70-80 with probable MCI in a 6-month randomized controlled trial. Teresa Liu-Ambrose, PhD, PT, of the University of British Columbia and Vancouver Coastal Health Research Institute, was the principal investigator of EXCEL and supervises Nagamatsu.
Compared with the balance and tone group, the resistance training group significantly improved performance on the Stroop Test, which measures selective attention and conflict resolution, and a memory task. Resistance training also led to functional changes in three brain regions involved in memory. In contrast, the aerobic training group did not show similar improvements.
"MCI is a critical window to intervene against dementia," Liu-Ambrose said. "We found that twice-weekly resistance training is a promising strategy to alter the trajectory of cognitive decline in seniors with MCI."
"Furthermore, we found that the aerobic training group had improved performance on a different memory task called the Rey Auditory Visual Learning Test. So both exercise groups improved their memory scores, but on different types of memory. More research is needed to determine the differential effects of these two types of exercise training," Nagamatsu added.
Higher functioning older adults may be more likely to show cognitive benefits from resistance training
Nader Fallah, PhD, and colleagues at the University of British Columbia, Vancouver used multi-state modeling* to investigate: 1) the simultaneous effect of exercise training and baseline factors on changes in executive cognitive function, and 2) the effect of exercise training on an individual's probability for cognitive improvement, maintenance, or decline.
*Multi-state models are models for processes that at any time occupy one of a few possible conditions or situations. For example, this model can be used to estimate the impact of physical activity on the individual probabilities of cognitive improvement, stability or decline. It allows analysis of changes in all directions, especially improvement – which has had relatively little attention but appears to be essential to understanding how neurodegenerative disease occurs.
Specifically, they performed a secondary analysis of a 12-month randomized, controlled clinical trial conducted in Vancouver of 155 community-dwelling women aged 65 to 75 years old who were randomly assigned to either resistance training or balance and tone training. The primary outcome measure was performance on the Stroop Test, an executive cognitive test of selective attention and conflict resolution. Teresa Liu-Ambrose, PhD, PT, of the University of British Columbia and Vancouver Coastal Health Research Institute, was the principal investigator of this study and supervises Fallah.
The scientists found that:
The probability of improving or maintaining results of the test were higher with resistance training among the study participants with higher function at beginning of the study.
Resistance training and balance and tone exercises had similar effect among those with lower function at baseline.
Overall, those in the balance and tone group demonstrated a significantly lower probability for improved performance on the Stroop Test, and a significantly higher probability of decline.
"To our knowledge, this is the first study to demonstrate that an individual's baseline self-regulatory capacity impacts the amount of cognitive benefit the person will reap from targeted exercise training," Fallah said.
"Before our study, we had no appreciation of the simultaneous impact of targeted exercise training and other factors, such as baseline cognitive status, on cognitive change in older adults. By using a multi-state transition model, we demonstrated that the probability of improving selective attention and conflict resolution in older adults is most evident among those with higher baseline cognitive status – which is different from the current general opinion," Liu-Ambrose said.
Combination training (aerobic + strength + balance) may improve memory in people with MCI
Hiroyuki Shimada, PhD, and colleagues at the National Center for Geriatrics and Gerontology, Obu, Aichi, Japan, conducted a randomized trial to test the impact of a 12-month, supervised, multicomponent exercise on cognitive function among older adults with amnestic (memory-related) MCI. The exercise program included aerobic exercise, muscle strength training, and postural balance retraining.
"Previous reviews suggested that combined aerobic exercise and strength training improved cognitive and physical functions more than aerobic exercise alone," Shimada said.
The final study population consisted of 47 older adults with amnestic MCI, 65 to 93 years old. Participants were randomized either to multicomponent exercise (n = 25) or an education control group (n = 25). People in the multicomponent exercise group exercised under the supervision of physiotherapists for 90 minutes/day, two days/week, 80 times for 12 months. People in the control group attended three education classes about health during the 12-month period. Measurements of cognitive function (Logical Memory II subtest of the Wechsler memory scale-revised, letter and category fluency, digit symbol coding, and Stroop color word test) were administered after six and 12 months.
The scientists found that the multicomponent exercise and educational program improved performance on Logical Memory II subtest of the Wechsler memory scale-revised. Additionally, there was a significant interaction effect for letter fluency test between groups.
"In other words, the ability to use language of the multicomponent exercise group improved significantly compared with the educational program group," Shimada said. "Our findings suggest that an exercise intervention can, at least partly, improve or maintain cognitive performance in older adults with amnestic MCI."