Six Months of Aerobic Exercise Cuts MCI Risk

Damian McNamara

December 20, 2018

Six months of aerobic exercise can improve executive functioning in patients with mild cognitive impairment (MCI), new research suggests.

In the Exercise and Nutritional Interventions for Cognitive and Cardiovascular Health Enhancement (ENLIGHTEN) study, researchers assessed 160 older adults who reported some cognitive impairment but no dementia.

Results showed significant improvements in executive functioning after six months of regular aerobic exercise. In contrast, participants randomly assigned to the Dietary Approaches to Stop Hypertension (DASH) diet did not demonstrate comparable improvements.

The patients who received a combination of both interventions showed the largest improvement compared with those who only received health education.

"The 'take home' message is that it is not too late for older adults with subtle cognitive impairments to adopt healthy lifestyle habits and to benefit from exercise and diet," principal investigator James A. Blumenthal, PhD, JP Gibbons Professor of Psychiatry, Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, North Carolina, told Medscape Medical News.

"Our data show that exercise improves executive functioning and also provide suggestive evidence that combining regular exercise with a heart-healthy diet reduces risk for heart disease and produces greater improvement in executive cognitive functioning compared to controls," he said.

The findings were published online December 19 in Neurology.

Good for the Heart, Good for the Brain?

"We were surprised to find that participants who engaged in regular aerobic exercise and who consumed the DASH diet...obtained greater improvements in executive functioning compared to participants who just received health education and did not exercise or modify their diets," Blumenthal said.

An overlap in risk factors for cardiovascular disease (CVD) and dementia means that strategies designed to reduce risk for CVD "also may be effective in improving neurocognition and reducing the risk of developing dementia," the investigators write.

"We believe that the benefits of diet and exercise have the potential for improving both heart and brain health," Blumenthal said.

"Our working hypothesis is that a healthier vascular system maximizes the brain's overall functioning and cognitive reserve," he added.

As reported by Medscape Medical News, American Academy of Neurology guidelines updated in 2017 support the cognitive benefits of exercise among people with MCI.

Individual studies in the literature also suggest aerobic exercise could improve neurocognitive function among healthy adults. However, relatively few studies include individuals with cognitive impairment, a meta-analysis revealed.

Other research has demonstrated an association between dietary factors and neurocognitive functioning. For example, multiple studies point to a cognitive benefit associated with the Mediterranean diet or DASH diet.

However, the current investigators point out that few published interventional studies assess "whole diets."

Literature Gap

To address this gap in the literature, they studied 160 older adults reporting cognitive impairment with no dementia (CIND). The cohort had subjective memory complaints and objective evidence of cognitive impairment. This degree of impairment does not meet diagnostic criteria but places people at increased risk for progression to dementia.

Participants scored 0.5 or greater on the Mail-in Cognitive Function Screening Instrument and scored 19 to 25 on the Montreal Cognitive Assessment, 12 or less on letter fluency or 15 or less on animal fluency.

In addition to being sedentary at baseline, they presented with one or more additional risk factors for CVD. For example, 21 participants had documented coronary heart disease and seven others had history of a transient ischemic attack without residual deficits.

The researchers enrolled the participants between December 2011 and March 2016 at the Duke Aging Center and the Duke Alzheimer's Disease Research Center. The mean age was 65 years, 66% were women, and whites and minorities were equally represented.

The investigators randomly assigned 41 participants to aerobic exercise alone, 41 to DASH alone, and 40 to a combination of the two interventions. In addition, 38 served as controls and only received health education.

Each session of aerobic exercise consisted of 10 minutes of warm-up exercises followed by 35 minutes of continuous walking or stationary cycling.

DASH is a diet high in fruits, vegetables, and low-fat dairy products approved in guidelines from the American Heart Association and American College of Cardiology.

Because this was a cognitive risk study, the investigators also assessed APOE status. They found that one third of 144 participants with this genetic risk information carried at least one APOE*E4 allele.

After six months, the investigators again assessed neurocognition, dietary consumption, cardiorespiratory fitness, and cardiovascular risk factors.

Improved Performance

The participants who engaged in aerobic exercise three times per week for 6 months demonstrated improved performance on a standard battery of neurocognitive tests of executive function.

For example, the exercise groups demonstrated significant improvements (b = 4.2, d = 0.32, P = .046) on a global measure of executive function.

Improvements in aerobic fitness (VO2 peak; b = 2.3, P < .049) and reduced CVD risk (b = 2.6, P < .042) among participants who exercised were also associated with improvements in executive function.

Compared with nonexercisers, those who regularly exercised also experienced significantly greater improvements in treadmill duration (P < .001), 6-minute walk distance (P < .001), and daily steps (P < .001).

For the DASH groups, a nutritionist provided education and solicited feedback on adherence in a series of half-hour sessions. The sessions were weekly for the initial 12 weeks and then every other week for weeks 13 to 24.

In contrast to the aerobic exercise groups, participants in the DASH diet groups experienced no significant changes in global executive functioning (b = 3.7, d = 0.30, P = .059).

"The DASH factor was not related to improved neurocognition, although we noted that greater benefits were observed among those participants who engaged in both exercise and the DASH eating plan compared to controls," the researchers write. Participants experienced reductions in total cholesterol, body weight, and the number of antihypertensive medications taken at follow-up.

"While this overall pattern of results may suggest a potential additive benefit of aerobic exercise and the DASH diet, we caution that our sample was small, and these findings must be interpreted with caution," they add.

Follow-up testing showed the largest improvements in the combination aerobic exercise and diet group (d = 0.40, P = .012) compared with the health education–only group.

This control group received weekly 30-minute educational phone calls for 3 months and then every other week for 3 months

Cognitive Age

The investigators also correlated their executive-function findings with predicted age. The Trail Making Test Parts A and B and Stroop Color-Word assessments, for example, allow clinicians to predict age based on scoring.

At baseline, performance was consistent with individuals at a mean age of 93 years, or about 28 years older than their chronologic age. After 6 months, however, executive function in the combination intervention group corresponded to an 8-year younger predicted age.

Interestingly, participants in the control group had a 6 months older predicted age compared with baseline, "which actually was the duration of the intervention," the researchers note.

"Efforts to identify 'at risk' individuals and to develop interventions that delay the progression of subclinical symptoms to overt dementia are critically important," Blumenthal said.

Dementia affects almost 10% of adults over age 65 years and more than twice as many individuals are affected by neurocognitive impairments short of meeting criteria for dementia, he added.

Because no currently available medications can reverse neurological changes in the brain, "strategies to slow the downward trajectory of cognitive decline in high-risk patients are needed," he said.

Crucial Role for Clinicians

Blumenthal acknowledged that information from this kind of research "is unlikely to be sufficient" to enact behavior change in patients at risk. Instead, he said that clinicians need to engage patients in the process and explain how lifestyle changes can improve brain health.

Counseling can help people identify barriers to behavior change. Blumenthal also recommended that clinicians devise a very specific plan for each patient that includes type, location, frequency, duration, and intensity of exercise to be performed.

Follow-up and monitoring are likewise important "to make sure they are able to make the behavioral changes," he said.

High internal validity, no dropouts among participants, and use of comprehensive neurocognitive testing are among the strengths of the study. Potential limitations include generalizability of the results to less motivated populations and under powering of results to compare the relative benefits of aerobic exercise vs the DASH diet directly.

"Further research is needed to confirm these findings in larger, more diverse samples and to understand the mechanisms by which lifestyle behaviors affect brain function," Blumenthal said.

"It also will be important to develop strategies to help people adopt, and sustain, healthy lifestyles throughout the lifespan," he added.

Evidence Backs Lifestyle Change

Asked to comment by Medscape Medical News, Glen R. Finney, MD, director of the Memory and Cognition Program, Neuroscience Institute, Geisinger Health System in Wilkes-Barre, Pennsylvania, told Medscape Medical News that the study "is another signal of the importance" of diet and exercise for brain health.

"I think it is interesting that they were able to see results with just 6 months of intervention," said Finney, who was not associated with the research.

"I suspect there is a trend here for the combination of diet and exercise over time to give even better results than just doing one change alone," he added.

"The results give more support for people with memory and thinking concerns to make healthy changes to their diet and exercise more, and it is useful to know that it may be possible to see results even in 6 months of follow up," he said.

The study was funded by a grant from the National Institutes of Health. Blumenthal and Finney have disclosed no relevant financial relationships.

Neurology. Published online December 19, 2018. Abstract

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