Effects of walking intensity on cognitive function in older adults with mild cognitive impairment (MCI): a pilot randomized controlled trial

Abstract

INTRODUCTION: Exercise is known to promote physical and mental health. The physical activity recommendations put forth by the World Health Organization can improve cardiorespiratory, metabolic, musculoskeletal, and functional health, prevent breast and colon cancer, as well as alleviating depression. However, the effects of these recommendations on cognitive health in older adults remain unknown. In 2018, the American Academy of Neurology reported that the relative risk for developing dementia in older adults with mild cognitive impairment (MCI) is 3.3 compared to cognitively normal older persons. As exercise provides a multitude of benefits for healthy aging, its efficacy in improving cognition in the MCI population therefore warrants investigation to supplement current physical activity guidelines. METHODS: The present study was a 12-week single-blind randomized controlled trial (RCT). Fifteen older adults (aged >= 50 years) with MCI (diagnosed by Montreal Cognitive Assessment – Hong Kong version (MoCA), using the 7th percentile of the age- and education-adjusted cutoff) were randomized to control (CON), once-a-week moderate-intensity walking (MOD), or once-a-week vigorous-intensity brisk walking (VIG). Subjects in the CON group (n = 5) performed light-intensity stretching, whereas subjects in the MOD group (n = 5) and the VIG group (n = 5) performed walking exercise on a motor-driven treadmill for 150 minutes at 3.5 METs and 75 minutes at 7 METs once a week respectively. RESULTS: After 12 weeks of intervention, the subjective cognitive ratings did not differ between the groups (p = 0.38). However, MoCA scores of both walking groups improved significantly compared to CON. MoCA of CON, MOD, and VIG improved by 1.1%, 30.9%, and 31.5% respectively (p< 0.001). MOD and VIG also performed better than CON in the Stroop colour test. The time required dropped by 8.3% in VIG, and increased by 0.6% in MOD and 54.5% in CON respectively (p < 0.001). VIG performed better than CON in verbal fluency in animals. The total number of responses increased by 21.8% in VIG, and dropped by 5.5% in CON (p = 0.003). VIG performed better than CON in forward digit span. The total number of correct responses increased by 3.6% in VIG, and dropped by 12.2% in CON (p = 0.034). CONCLUSION: Twelve weeks of walking training led to significant improvement in MoCA scores compared to control conditions, which also prevented the decline in cognitive functions in older adults with MCI. Despite no significant differences in any neurocognitive tests between the walking groups, vigorous-intensity brisk walking might be more beneficial as it prevented the decline in multiple cognitive domains, including executive function and working memory, while moderate-intensity walking only prevented the decline in Stroop colour test performance compared to control conditions. RCTs with larger sample sizes are warranted to validate the effects of walking intensity on improving cognitive functions in older adults with MCI.