Older adults with mild cognitive impairment but no dementia, who were at risk for cardiovascular disease, improved their executive functioning—the ability to plan, focus, remember instructions, and perform multiple tasks—after six months of regular aerobic exercise.
In addition, a combination of both aerobic exercise and the Dietary Approaches to Stop Hypertension (DASH) diet led to even greater improvement, according to results of the ENLIGHTEN (Exercise and Nutritional Interventions for Cognitive and Cardiovascular Health Enhancement) study published online in Neurology on December 19.
Studies have demonstrated that exercise can reduce the risk of cardiovascular disease and of developing dementia. To date, the effect has been seen in healthy adults not those with cognitive impairments.
Similarly, a healthy diet like the DASH diet—part of the national recommendations for preventing and treating high blood pressure—has been associated with improved cognition. The DASH diet, in particular, lowers blood pressure, reduces other cardiovascular risk factors, and reduces the risk of heart disease and stroke.
To find out if regular exercise and the DASH diet could improve executive function and memory in older adults who had mild cognitive impairment but no dementia and were at risk for cardiovascular disease, researchers enrolled 160 participants at the Duke Aging Center and the Duke Alzheimer's Disease Research Center between December 2011 and March 2016. The average age of participants was 65 years; 66 percent were women; and 50 percent were white.
All participants underwent cognitive testing at the start of the study and were assessed for cardiovascular disease risk factors such as high blood pressure. The researchers then randomly assigned 41 participants to aerobic exercise alone, 41 to DASH alone, and 40 to a combination of aerobic exercise and DASH. The 38 people in the control group had weekly 30-minute phone calls about health-related topics for three months and then every other week for three months.
Those in the aerobic exercise group did 10 minutes of warm-up exercises followed by 35 minutes of continuous walking or stationary cycling three times a week for six months under supervision. Participants recorded their workouts in a weekly exercise log. Those following the DASH diet met with nutritionists for weekly half-hour sessions for the first 12 weeks and then biweekly for the next 12. Those in the exercise and diet group followed both protocols.
At six months, participants took the same set of cognitive tests they did at the beginning and researchers assessed their diet, cardiorespiratory fitness, and cardiovascular risk factors.
After six months, participants in the exercise group showed significant improvements in executive function. Those in the DASH diet group saw no significant changes in executive function. Those in the combined exercise and DASH diet group saw the largest improvements. For example, at the beginning of the study, participants' average executive function was equal to that of a 93-year-old—28 years older than their average chronological age. In six months, those who exercised and followed the DASH diet had average executive function scores of an 84-year-old—a nine-year improvement.
In comparison, the executive function scores for the control group worsened by a half year.
All participants had at least one cardiovascular risk factor, including coronary heart disease and a history of transient ischemic attack.
Participants following the DASH diet lowered their total cholesterol as well as LDL cholesterol, lost weight, and reduced the number of blood pressure medications they were taking.
Participants in the exercise group and the combination exercise and diet group lowered their blood sugar levels, and the diet-exercise group improved executive function.
The researchers hypothesized that because cardiovascular disease and dementia share risk factors, any strategies that reduce cardiovascular risk also may be effective in improving cognition and lowering the risk of dementia.
The trial was too short to measure the long-term effects of exercise and diet on cognitive outcomes, the researchers noted, adding that a longer study with a larger sample size is needed to observe how diet and exercise help improve cognitive functioning.