Background Cognitive frailty is the coexistence of physical frailty and cognitive impairment and is an at-risk state for many adverse health outcomes. Moderate-to-vigorous physical activity (MVPA) is protective against the progression of cognitive frailty. Physical inactivity is common in older people, and brisk walking is a feasible form of physical activity that can enhance their MVPA. Mobile health (mHealth) employing persuasive technology has been successful in increasing the levels of physical activity in older people. However, its feasibility and effects on older people with cognitive frailty are unclear. Objective We aimed to identify the issues related to the feasibility of an mHealth intervention and the trial (ie, recruitment, retention, participation, and compliance) and to examine the effects of the intervention on cognitive function, physical frailty, walking time, and MVPA. Methods An open-label, parallel design, randomized controlled trial (RCT) was employed. The eligibility criteria for the participants were age ≥60 years, having cognitive frailty, and having physical inactivity. In the intervention group, participants received both conventional behavior change intervention and mHealth (ie, smartphone-assisted program using Samsung Health and WhatsApp) interventions. In the control group, participants received conventional behavior change intervention only. The outcomes included cognitive function, frailty, walking time, and MVPA. Permuted block randomization in 1:1 ratio was used. The feasibility issue was described in terms of participant recruitment, retention, participation, and compliance. Wilcoxon signed-rank test was used to test the within-group effects in both groups separately. Results We recruited 99 participants; 33 eligible participants were randomized into either the intervention group (n=16) or the control (n=17) group. The median age was 71.0 years (IQR 9.0) and the majority of them were females (28/33, 85%). The recruitment rate was 33% (33/99), the participant retention rate was 91% (30/33), and the attendance rate of all the face-to-face sessions was 100% (33/33). The majority of the smartphone messages were read by the participants within 30 minutes (91/216, 42.1%). ActiGraph (58/66 days, 88%) and smartphone (54/56 days, 97%) wearing compliances were good. After the interventions, cognitive function improvement was significant in both the intervention (P=.003) and the control (P=.009) groups. The increase in frailty reduction (P=.005), walking time (P=.03), step count (P=.02), brisk walking time (P=.009), peak cadence (P=.003), and MVPA time (P=.02) were significant only in the intervention group. Conclusions Our mHealth intervention is feasible for implementation in older people with cognitive impairment and is effective at enhancing compliance with the brisk walking training program delivered by the conventional behavior change interventions. We provide preliminary evidence that this mHealth intervention can increase MVPA time to an extent sufficient to yield clinical benefits (ie, reduction in cognitive frailty). A full-powered and assessor-blinded RCT should be employed in the future to warrant these effects. Trial Registration HKU Clinical Trials Registry HKUCTR-2283; http://www.hkuctr.com/Study/Show/31df4708944944bd99e730d839db4756

BACKGROUND Cognitive frailty is a co-existence of both physical frailty and cognitive impairment and an at-risk state for many adverse health outcomes, including dementia, dependency, and mortality. Moderate to vigorous physical activity (MVPA) is protective against the progression of cognitive frailty. Physical inactivity is still common in older people. Brisk walking is a feasible form of physical activity for older people to practise to enhance their MVPA. M-health employing persuasive technology has been successful to increase their levels of physical activity. However, its feasibility and effects on older people with cognitive frailty are unclear. OBJECTIVE The aims of this study were to 1) identify issues relating to the feasibility of the intervention and the trial, and 2) examine the effects of the intervention on cognitive function, physical frailty, walking, and MVPA. METHODS An open-label, two-parallel-groups, randomized controlled trial (RCT) was employed. The eligibility criteria were 1) ≥ 60 years, 2) having cognitive frailty, and 3) having physical inactivity. In the intervention group, participants received both conventional behavioural change and m-health (i.e., smartphone-assisted programme using Samsung Health and WhatsApp) interventions. In the control group, participants received conventional behavioural change intervention only. The outcomes included cognitive function, frailty, walking, and MVPA. Permuted block randomization in a ratio of 1:1 was used. Issue of feasibility was described in terms of subject recruitment, retention, participation and compliance. Wilcoxon sign-rank test was used to test the within-group effects in both groups separately. The level of significance was 0.05. RESULTS We recruited 99 subjects and 33 eligible subjects were randomized into either intervention (n=16) or control (n=17) group. Their median age was 71.0 years (IQR=9.0) and the majority of them were female (n=28, 85%). The recruitment rate was 33%, the subject retention rate was 90%, the attendance rate of all face-to-face sessions was 100%. The majority of smartphone messages were read the participants within 30 minutes (42.1%). ActiGraph (88%) and smartphone (94%) wearing compliances were good. After the interventions, cognitive function improvement was significant in both the intervention (P=.003) and control (P=.009) groups. Frailty reduction (P=.005), walking-time increase (P=.03), step-count increase (P=.02), brisk-walking time increase (P=.009), peak-cadence increase (P=.003), and MVPA time increase (P=.02) were significant only in the intervention group. CONCLUSIONS It is feasible to implement this m-health intervention in older people with cognitive impairment. The m-health intervention is effective at enhancing compliance with the brisk-walking training programme delivered by conventional behavioural change interventions. This study provided preliminary evidence that this m-health intervention can increase MVPA time to an extent sufficient to yield clinical benefits (i.e., a reduction in cognitive frailty). Further studies should employ a full-powered and assessor-blinded RCT to warrant these effects. CLINICALTRIAL This pilot randomized controlled trial has been registered with the Hong Kong University Clinical Trials Registry (HKUCTR-2283, http://www.hkuctr.com/Study/Show/31df4708944944bd99e730d839db4756).