Effectiveness of Walking Exercise in Improving Cognitive Function in Older Adults With Mild Cognitive Impairment

Effectiveness of Different Exercise Intensities and Frequencies of Walking Exercise on Improving Cognitive Function in Older Adults With Mild Cognitive Impairment: a Pilot Randomized Controlled Trial

The increasing prevalence of mild cognitive impairment (MCI) in our rapidly aging population prompts the need for devising effective interventions to prevent the onset of cognitive impairment and delay its progression to dementia. The benefits of aerobic exercise on the cognitive function in older adults with MCI are well-documented. However, exercise protocols and outcome measurement tools in the current literature are highly heterogeneous. It is therefore imperative to develop standard exercise prescription protocol for the MCI population or to examine the effectiveness of the existing, well-established exercise guidelines. The World Health Organization (WHO) recommends adults (18 - 64 years of age) and older adults (65 years and older) to perform 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic physical activity per week to improve cardiorespiratory and muscular fitness, bone health, and reduce the risk of non-communicable diseases and depression. Nonetheless, few studies have determined the effectiveness of the WHO Global Recommendations on Physical Activity for Health guideline in improving cognitive function in older adults with MCI. This study thus aims to evaluate the effectiveness of the WHO Physical Activity Recommendations in improving cognitive function in older adults with MCI. In 2017, the American Academy of Neurology (AAN) updated the Practice Guideline for Mild Cognitive Impairment, in which they recommended patients diagnosed with MCI to perform exercise at least twice a week for at least 6 months to gain cognitive benefits. This recommendation was based on two class-II studies, in which a 6-month twice-a-week 90-minute multicomponent exercise program helped maintain global cognition, and selective attention improved significantly following a 6-month twice-a-week 60-minute multicomponent exercise program. While they provided pivotal insights into clinical practice, there were several limitations for these two studies. For instance, in the study conducted by Nagamatsu et al., only female subjects were recruited, and therefore lead to low generalizability. These two studies focused on multi-component exercise intervention which included resistance training, aerobic training, and balance training, and the duration of each component was short (around 20 - 30 minutes). Studies that focus on single exercise modality with longer session duration are warranted to unveil the efficacy of a certain exercise modality in improving cognitive function. In this study, we will evaluate the effectiveness of aerobic exercise on improving cognitive function in older adults with MCI. We intend to follow the WHO Recommendations, focusing on evaluating the effect of different exercise intensities (moderate versus vigorous) and frequencies (once versus thrice per week) of aerobic exercise on improving the cognitive function in older adults with mild cognitive impairment. In particular, the AAN also suggested that physical activity of at least twice a week is necessary to produce cognitive benefits. We, therefore, aim to investigate whether one session per week would also suffice to improve the cognitive function in older adults with MCI.

Aims: To examine the effectiveness of 12-week WHO Global Recommendations on Physical Activity for Health in practice in improving the cognitive function in older adults with MCI.

Inclusion Criteria:

1. Older adults aged ≥ 50 years old;
2. Ethnic Chinese;
3. Diagnosed with mild cognitive impairment (MCI) under the Mayo Clinic criteria [8-10]: 1). Subjective complaint about a decline in cognitive function; 2). Total score in the Hong Kong version of the Montreal Cognitive Assessment is below the 7th percentile of the age- and education-corrected normative data of Hong Kong; 3). The decline in cognitive function does not impair daily functioning, as revealed by getting ≥ 2 marks in every item on the Chinese Lawton Instrumental Activities of Daily Living Scale (4-point Scale).

Exclusion Criteria:

1. Diagnosis of dementia/Alzheimer's disease, or currently using antidementia medication;
2. Incapable of participating in physical exercise with major confounding conditions that are known to affect mobility. Specifically designed questionnaires will be used to screen for exclusion criteria including 1). Cannot walk without assistive device; 2). Any serious somatic condition that prevents walking exercise participation.
3. History of major diseases e.g. cancer, cardio-/cerebrovascular, neurodegenerative and renal diseases;
4. Diagnosis of psychiatric diseases, or currently using psychiatric medication.