We all know the benefits of engaging in a consistent physical activity routine. Stronger hearts, lungs, muscles and bones lead the list of short-term benefits. Improved sleep and better weight management shine as medium-term benefits. Less chronic disease and greater longevity stand atop the list of long-term benefits.
In fact, many studies have shown that engaging in a program of regular physical activity literally delays or reverses the aging process. We’ve previously written about a few of these studies that have shown those who continue to exercise and otherwise stay physically active into their golden years often exhibit strength and stamina of people 20 to 30 years younger.
And according to a new study published this month in the journal Archives of Internal Medicine, engaging in regular physical activity also seems to preserve mental/cognitive function. In fact, the study results showed the most physically active study subjects had cognitive function comparable to adults five to seven years younger.
To be fair, the study population in this research endeavor was limited to senior women with cardiovascular disease (CVD), and there is a known connection between depressed mental function and poor vascular health. However, the same journal published another study in the same issue that showed that among older adults (men and women) with no known life-threatening illnesses, those who were most active were 91% less likely to incur cognitive impairment in comparison to those in the study who were least active.
The point here is that regular physical activity seems to delay the effects of aging in both mind and body.
You Don’t Have to Work Out to Exercise
Before describing the two studies in a bit more depth, it is important to understand how the researchers in both studies defined physical activity. One’s mind immediately assumes the researchers meant exercise.
While traditional exercise workouts certainly fall into the category of moderate to vigorous physical activity, the researchers in both studies also included low-intensity daily activities that require movement of one kind or another. Activities such as walking up or down stairs, doing chores, shopping, gardening and movement while at work were included in the subjects’ accounting of regular physical activity.
Exercise to Keep Your Mind Young
With that definition in mind, the first study examined the relative cognitive abilities of over 2,800 women with an average age of 72 who either were already diagnosed with cardiovascular disease or who had three or more coronary risk factors from among diabetes, hypertension, high cholesterol and high body mass index.
At the outset of the study, the women completed questionnaires about their daily physical activities, including both exercise-related activity and the lower-intensity daily living activities described above. Every two years thereafter until the study concluded, the women were asked to complete the activity questionnaire again.
To assess mental function, each woman participated in a telephone interview that included five memory and cognition tests. Over the following five years, the memory/cognition tests were taken again by subjects on three separate occasions.
The researchers then split the women into five equal-sized groups of increasing levels of physical activity and looked at each group’s relative performance on the cognition tests. At one end of the spectrum, the women in the lowest quintile were active for only 0.6 hours per week. At the other end, the women in the highest quintile were active for 38.9 hours per week. For comparison purposes, the women in the second highest quintile were active for 15.4 hours per week. The researchers found significant reductions in cognitive decline in the two highest quintiles of physical activity.
In looking at the quintiles more closely, the researchers observed that walking was the most prevalent form of activity noted by study subjects, accounting for roughly 33 percent to 45 percent of total physical activity hours between the five groups. Of the total activity hours noted above, the lowest quintile registered 0.2 hours per week of walking, while the second-highest activity quintile logged 6.7 hours per week, and the highest activity group registered 13.7 hours per week. The research team noted that the walking component of the two top quintiles was equivalent to a minimum of 30 minutes per day of brisk walking.
In comparing the results of the five cognitive tests with these varying levels of physical activity they discovered a strong inverse relationship, i.e., the higher the activity level the lower the level of cognitive loss. In particular, the study authors noted that the women in the two highest quintiles of activity had cognition scores on the five tests that were comparable to scores recorded on those tests by a general adult population sample who were five to seven years younger.
The results of the study led the authors to conclude, “In this large prospective study of women with preexisting CVD or vascular risk factors at high risk of cognitive decline, greater physical activity was associated with substantially slower cognitive decline. Participating in the 2 highest quintiles of physical activity was cognitively equivalent to being 5 to 7 years younger. Most important, the association with total physical activity was not restricted to women engaged in vigorous exercise; higher levels of walking for exercise were significantly related to less cognitive decline.”
In the second study we noted earlier in this article, researchers studied the connection between “activity energy expenditure” and cognitive decline in 197 adults with an average age of approximately 75 (roughly 50/50 split between men and women in the study).
As in the previous study, the researchers had study participants complete physical activity questionnaires and take a standardized cognition test (the cognition tests were taken at baseline and again three to five years later). In addition, the researchers also included a diagnostic test to assess the energy expended by participants called “doubly labeled water.” This test apparently is the gold-standard for assessing energy expended through activity. In short, it is a technique that helps calculate a person’s metabolic rate (how much energy they burn). We’ll leave it at that because, honestly, it would take an additional 1,000 words to explain the technique and a medical degree to understand it. But if you’re interested in learning more about the doubly labeled water technique, be our guest and click here.
With all of the test results in hand, the researchers in this latter study divided the participants into three equal sized groups (as opposed to five described in the earlier study) based on the participants differing levels of “activity energy expenditure” or AEE. Then the researchers looked across the tertiles to see if there were noteworthy correlations in self-reported physical activity and changes in cognition test scores over the study period.
They found a strong correlation between the AEE test results and self-reported physical activity. For example, the researchers calculated that the lowest AEE tertile expended the equivalent of 76 calories per day through physical activity, while the middle third averaged 251 calories burned/day, and the highest tertile expended an average of 323 calories/day.
Much like the earlier study discussed in our article, most of the calculated calories were associated with low-intensity physical activities such as walking. For reference sake, a 130-pound individual burns roughly 150 calories walking for 30 minutes at a brisk pace, while a 200-pound person burns approximately 230 calories.
The study team also found a strong inverse relationship between AEE/physical activity and changes in cognition scores between the baseline and follow-up tests. For example, the results showed that the subjects in the highest AEE/physical activity tertile incurred 91% less incidence of cognitive impairment over the three-to-five-year follow-up period compared to the lowest tertile. The middle tertile also demonstrated significantly less (72%) incidence of cognitive impairment versus the lowest activity group over the same follow-up period.
While scientists do not fully understand why exercise seems to preserve cognitive function, the researchers in the first study discussed here offered their speculation: “Various biologic mechanisms may explain the positive relation between physical activity and cognitive health. Exercise may directly preserve neuronal structures by stimulating brain-derived neurotrophic factor and neuronal growth, possibly providing reserve against cognitive decline and dementia. Exercise may also have indirect effects by strengthening the underlying systems that support brain plasticity and helping to sustain the brain’s vascular health by beneficially influencing cardiovascular risk factors, promoting endothelial function, improving glucose and insulin regulation, and ensuring adequate cerebral perfusion. Furthermore, physical activity reduces inflammation, which is higher in those with vascular disease, and impairs systemic and brain-specific growth factor signaling. Physical activity may also improve psychological well-being, which in turn may protect against decline in cognitive functioning.”
Regardless of the underlying mechanism, the results of these two studies seem clear. Regular physical activity keeps the mind young and you can achieve these benefits with as little as 30 minutes per day of brisk walking.
 Vercambre MN, et al. Physical Activity and Cognition in Women With Vascular Conditions. Arch Intern Med. 2011 July 25; 171(14): 1,244-1,250.
 Middleton LE, et al. Activity Energy Expenditure and Incident Cognitive Impairment in Older Adults. Arch Intern Med. 2011 July 25; 171(14): 1,251-1,257.