Research Brief: Total Activity, Not Just Exercise, Keeps Mind Sharp
8 May 2012. Although a growing number of studies suggest that exercise can keep an aging brain honed and perhaps ward off dementia, only a couple of those studies have included objective measures of activity (see ARF related news story on Middleton et al., 2011; Barnes et al., 2008; see also AlzRisk report on physical activity). To better quantify the effect of exercise, researchers led by Aron Buchman at Rush University, Chicago, Illinois, measured total daily activity in more than 700 healthy seniors, average age 82, who participated in the Rush Memory and Aging Project. The volunteers wore an actigraph device (Actical brand), which records all movements, on their wrists around the clock for about nine days. In the April 24 Neurology, the authors report that participants with the highest levels of total daily activity had a slower rate of cognitive decline and about half the risk of developing Alzheimer’s disease over the next four years than the least active participants. Intriguingly, the participants’ self-reported physical activity showed no association with Alzheimer’s risk. This suggests that either the self-reports were inaccurate, or that non-exercise types of activity, such as housework, gardening, or even fidgeting might be as important for brain health as exercise is, the authors suggest. As this was an observational study, however, it could not prove a causal connection between activity and cognitive decline.
Compared to studies that rely on self-reports, “Most studies that have used objective measures of activity have found a stronger association between activity and cognitive function,” Deborah Barnes at the University of California, San Francisco, wrote to Alzforum, noting the need for more such studies. She was not involved in the work.
Meanwhile, researchers led by Teresa Liu-Ambrose at the University of British Columbia, Vancouver, Canada, wanted to compare the effects of resistance training (i.e., weight lifting) and aerobic exercise on cognition. In the April 23 Archives of Internal Medicine, they report that in a small proof-of-concept clinical trial, 26 elderly women with probable mild cognitive impairment (MCI) who took twice-weekly resistance training classes for six months significantly improved their performance on the Stroop test of executive function compared to a control group of 27 age-matched volunteers who received balance and stretching classes. In comparison, the 24 participants who received aerobic training did not show consistent or significant cognitive gains in this trial, although other studies have found that aerobic training does improve cognition (see, e.g., Colcombe et al., 2004; Baker et al., 2010). First author Lindsay Nagamatsu told Alzforum by e-mail that these studies included more frequent and intense aerobic exercise, which might explain the differing results.
Though preliminary, the data suggest that larger trials to explore the benefits of resistance training might be warranted, the authors write, especially in the MCI population, which is at high risk for AD. The new study builds on previous work from this group showing that 12 months of weight lifting improves test performance in cognitively healthy elderly women (see Liu-Ambrose et al., 2010; Liu-Ambrose et al., 2011). Eric Larson at Group Health Research Institute, Seattle, Washington, noted that if these results hold up, it could fundamentally change the way people approach exercise programs for the elderly, where muscle strength is sometimes overlooked.
What do these studies mean for exercise as an intervention? In 2010, a National Institutes of Health (NIH) state-of-the-science panel concluded that there was insufficient evidence to show that any intervention prevents or delays AD, although exercise was found to be consistently associated with lowered risk (see ARF related news story; ARF news story). Barnes’ view is that, at this point, “We can definitively say that exercise improves cognitive function. We don’t yet know for sure whether this cognitive improvement translates into delayed dementia onset or dementia prevention.” To prove this connection will require larger, longer clinical trials with dementia as the primary outcome, she noted, although such trials may be difficult to conduct.
In addition to physical activity, social and cognitive activity have been associated with keeping brains young (see, e.g., ARF related news story; ARF news story; and ARF news story), although specific types of cognitive training have fallen short in some trials (see ARF related news story; ARF news story). Buchman’s results bear out these associations, with his data showing that self-reported social and cognitive activity each provided separate, cumulative benefits in decreasing the risk of AD for the Rush Study participants. “The whole range of late-life activities, physical, cognitive, and social, all seem to be beneficial. This is actually very empowering for older people,” Buchman told Alzforum, adding that someone with physical limitations that prevent exercise can stay active in other ways.
In future studies, Buchman would like to narrow down what types and amounts of activity are the most beneficial. Researchers will need these data before they can make specific public health recommendations, he said. Because participants in the Rush Study donate their brains after death, Buchman will also be able to examine whether there is any link between brain pathology and a person’s levels of activity in life.—Madolyn Bowman Rogers.