INVESTIGATING THE EFFECT OF AEROBIC EXERCISE ON COGNITIVE FUNCTION IN OLDER ADULTS

Abstract

Aging is associated with cognitive decline and an increased risk for neurodegenerative disease. Physical exercise may be an effective intervention to enhance cognitive function in older adults; however, the optimal dose for maximal cognitive benefit is unknown. Additionally, the mechanism through which exercise may promote cognition in older adults is poorly understood. The present study investigated the effect of aerobic exercise intensity on cognitive function in three domains: memory, processing speed, and executive functions. Brain-derived neurotrophic factor (BDNF), a protein that supports the growth and survival of neurons, was examined as a potential mechanism underlying the effect of exercise on cognition. Sixty-four sedentary older adults (39 females; mean age=72 years; age range=60-88 years) were randomly assigned to one of three groups: 1) high-intensity interval training group (HIIT; n=21), 2) moderate continuous training group (MCT; n=20), or 3) active control group (n=23). Cognitive function was assessed pre- and post-intervention using a Mnemonic Similarity Task (memory), a Go-nogo task (processing speed and executive function), and a Flanker task (executive function). Serum BDNF concentrations were assessed using enzyme-linked immunosorbent assays (ELISAs). It was hypothesized that HIIT would result in the greatest cognitive benefit, followed by MCT. The control group was not expected to improve. It was predicted that improvements in cognition would be accompanied by increases in serum BDNF. HIIT resulted in better performance on the Mnemonic Similarity Task [F(2, 55)=6.04, p=0.004] compared to both MCT and control. The MCT group had faster processing speed on the Go-nogo task [F(2, 59)=4.16, p=0.02] compared to control. HIIT and MCT both had a trend toward better performance on the Go-nogo task [F(2, 59)=2.54, p=0.088] compared to control. Only HIIT resulted in a trend toward better performance on the Flanker task [F(2, 56)=2.41, p=0.099] compared to both MCT and control. No significant differences were found in BDNF concentration between groups. This is one of the first trials to directly compare the effect of different intensities of aerobic exercise on cognitive function. Consistent with prior literature, the results suggest that aerobic exercise can enhance cognitive function in older adults, and critically, HIIT was the most effective. However, BDNF may not mediate the changes in cognition in older adults. This research may help inform exercise prescription for optimal cognitive health in the growing population of older adults.