BY LIZETTE BORRELI
Six months of regular aerobic exercise helped older adults with mild cognitive impairment (MCI) with no dementia and at risk for cardiovascular disease (CVD) improve their executive functioning, but not memory or language/verbal fluency, according to a randomized clinical trial published online on December 19 in Neurology.
Moreover, a combination of both aerobic exercise and the DASH (Dietary Approaches to Stop Hypertension) diet led to the largest improvement compared to controls.
"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," principal investigator James A. Blumenthal, PhD, JP Gibbons Professor of Psychiatry at Duke University Medical Center in Durham, NC, and his colleagues wrote.
The ENLIGHTEN (Exercise and Nutritional Interventions for Cognitive and Cardiovascular Health Enhancement) trial aimed to investigate whether older adults with MCI but not dementia and cardiovascular disease risk factors (CVD) could improve executive functioning, memory, and verbal fluency by adding regular aerobic exercise, and/or the DASH diet.
The team enrolled 160 sedentary participants at the Duke Aging Center and the Duke Alzheimer's Disease Research Center between December 2011 and March 2016. The average age of the participants was 65 years; 66 percent were women; and were evenly divided between whites and minorities.
The researchers randomly assigned 41 participants to aerobic exercise alone, 41 to DASH alone, and 40 to a combination of aerobic exercise and DASH. Thirty-eight participants served as controls and only received health education via weekly 30-minute phone calls about health-related topics for three months and then biweekly for three months.
The aerobic exercise intervention consisted of 10 minutes of warm-up exercises followed by 35 minutes of continuous walking or stationary cycling three times a week for six months at 70 to 85 percent of their initial peak heart rate reserve for three months under supervision. Participants recorded their workouts in a weekly exercise log.
In the DASH diet intervention, participants received education and feedback on adherence by a nutritionist in a series of half-hour sessions by a nutritionist conducted weekly for the initial 12 weeks and then biweekly for weeks 13 to 24.
At six months, the researchers assessed neurocognition, dietary consumption, cardiorespiratory fitness, and cardiovascular disease risk (CVD) factors. Those who regularly engaged in aerobic exercise showed significant improvements (p = .046) in executive function. Compared to the exercise groups, the DASH diet groups experienced no significant changes in executive functioning (p = .059).
Among those who exercised, improvements in aerobic fitness (VO2 peak; p < .049) and reduced CVD risk (, p < .042) were also linked to improvements in executive function.
Greater improvements in treadmill duration (p < .001), 6-minute walk distance (p < .001), and daily steps (p < .001) were also seen.
Participants in both interventions saw the largest improvements in executive functioning (p = 0.012).
CVD risk factors decreased for those on the DASH diet, including total cholesterol, reduced weight and LDL lipoprotein, and a reduction in the number of hypertensive medications taken. Insulin improvements were seen in the exercise alone and the exercise and DASH diet groups.
Although the DASH diet was not associated with significant improvements in executive function, those in the aerobic exercise arm of the exercise and DASH group did reap benefits in executive function. Moreover, a reduction in sodium intake was also associated with improved executive function. Changes in potassium, magnesium, and calcium were not related to executive function.
The researchers believe "because there is considerable overlap in risk factors for CVD and dementia, strategies designed to reduce CVD risk also may be effective in improving neurocognition and reducing the risk of developing dementia."
At least one CVD risk factor was present in study participants. For example, 21 had coronary heart disease and an additional seven had a history of transient ischemic attack without residual deficits.
The study author acknowledged that the trial was underpowered to detect differences between exercise and the DASH diet alone, which provides limited evidence on the relative benefits of these two interventions. In addition, the trial was only six months long; the researchers were unable to measure the long-term effects of exercise and diet on cognitive outcomes. Lastly, participants were highly motivated and did not drop out; these findings may not apply to less motivated groups.
A grant from the National Institutes of Health funded the study. The researchers reported no financial disclosures.
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Blumenthal JA, Smith PJ, Mabe S, et al. Lifestyle and neurocognition in older adults with cognitive impairments: A randomized trial. Neurology 2018; 2018 Dec 19.