| Objectives: With the escalation of the aging population worldwide, cognitive impairment and dementia has become a major public health concern. Early diagnosis and treatment are becoming critically important in order to reduce the prevalence of dementia in the elderly. Mild cognitive impairment(MCI) is a transitional state between healthy aging and dementia. Elderly individuals with MCI are at higher risk for developing AD. Given that no effective pharmacological treatment exists for individuals with MCI to alter or slow the progression of cognitive decline, there has been growing interest in adopting lifestyle-change approaches, such as exercise, to prevent and/or reduce risk of developing dementia. Randomized controlled studies have demonstrated that combined cognitive and exercise training(eg, Tai Ji, cognitive-exercise intervention) may well provide greater cognitive benefits. Thus, exercise is a promising intervention for improving cognitive functions in older adults. Beside cognitive impairment, older adults also experience decline of motor control, affecting health and independence of old people, both of which influence each other. Momentum-based dumbbell training is a self-initiated spinning exercise that uses dumbbells to generate momentum while performing exercise movements with varying configurations aimed at concurrently challenging physical and cognitive abilities. In this proof-of-concept study, the main purpose of our study was to examine the feasibility of application and the potential effects of momentum-based dumbbell training on cognitive function in older adults with MCI. A secondary purpose was to examine its effects on physical function, quality of life and sleep quality.Methods: This thesis included two studies: a feasibility study(study 1) and randomized controlled trial(study 2). Study 1: A validation study was conducted to initially test the feasibility as well as the effectiveness of momentum-based dumbbell training, which used a single group repeated-measures design. A total of 12 participants(mean age 58.3 years) were recruited to participate in the dumbbell training program for 4 weeks. All outcome measures were undertaken at baseline and post-intervention, including physical performance, physical health, quality of life and sleep condition. Study 2: A randomized controlled trial was further conducted to compare theeffects of a 12-week momentum-based dumbbell training in older adults with MCI. Forty-five community-dwelling older adults with MCI were randomly assigned to either a dumbbell training group(DTG; n=22, mean age 69.0 years) or a control group(CG; n=23, mean age 70.4 years). Participants in the DTG participated in exercise sessions 3 times weekly for 12 weeks. All outcome measures were undertaken at baseline and post-intervention. The primary outcome measure was total score of Alzheimer’s Disease Assessment Scale-Cognitive subscale(ADAS-Cog), with secondary outcome measures being Mini-Mental State Examination(MMSE), Montreal Cognitive Assessment(Mo CA), Trail Making Test-part A and B(TMT-A/B), Digit Span Test-Forward/Backward(DST-F/B), Reaction Time(RT), Timed Up & Go(TUG), Functional Reach(FR), Berg Balance Scale(BBS), Timed 10 m walking, the Activities-specific Balance Confidence Scale(ABC), proprioception(kinaesthesia) test, stabilometer test, SF-36 survey and Pittsburgh Sleep Quality Index(PSQI).Results: Study 1: At post-intervention, the participants showed significant improvements in physical function(10m-walking, TUG, FR, BBS; P<0.05), physical health(weight, BMI, arterial pressure at rest; P<0.05) and quality of life(P<0.05). Study 2: The average attendance for the DTG was 31 sessions(85%). In an intentto-treat analysis, the main results as follows: 1) Cognitive function: At post intervention, participants in the DTG, compared to those in the CG, had significantly improved ADAS-Cog total score(5.02 points, F=6.95, P=0.012), word recall(0.49 points; F=9.08, P<0.01) and attention scores(0.43 points; F=5.22, P=0.02), and MMSE score(1.23 points; F=4.84, P=0.03). There was a significant within-group changes(improvement) in ADAS-Cog total score(t=-2.34, P=0.03), MMSE(t=2.00, P=0.06), Mo CA(t=3.85, P<0.01), TMT-A(t=-2.80, P=0.01), TMT-B(t=-3.09, P=0.01) and DST-B(t=2.41, P=0.03). 2) Physical function: At post intervention, participants in the DTG improved their functional mobility(TUG=0.81 s, F=4.34, P=0.043), sway speed on X and Y axis(standing with single-leg and eye-opened; 10.56mm/s; F_X=5.71, P_Y=0.02; 14.96mm/s; F_Y=4.33, P_Y=0.04), compared to those in the CG. There was a significant within-group changes(improvement) in functional mobility(TUG, t=3.38, P<0.01), kinaesthesia of dorsiflexion and extroversion of ankle(t=-2.55, P=0.02;t=-2.54, P=0.02), kinaesthesiaof flexion of knee(t=-2.39, P=0.03) and deviation on Y axis(standing with two-leg and eye-closed, t=2.34, P=0.03); meanwhile, there were also some significant within-group changes(improvement) observed in CG, including BBS(t=2.52, P=0.02) and kinaesthesia of flexion of knee(t=-2.13, P=0.047). There was no significant relationship between cognitive improvement and changes in most measures of physical functions, apart from deviation(r MMSE=0.443, P=0.02; r Mo CA =0.473, P=0.02) and sway speed(r DSTF=-0.398, P=0.04) on Y axis(standing with two-leg and eye-closed) and kinaesthesia of flexion of knee(r DSTF=0.476, P=0.01). 3) Quality of life and sleep quality: At post intervention, participants in the DTG, compared to those in the CG, had significantly improved SF-36 physical functioning(9.55 points; F=4.14, P=0.048) and vitality(16.51 points; F=4.27, P=0.04), PSQI total score(1.43 points; F=4.08, P=0.05) and sleep efficiency score(0.12 points; F=7.13, P=0.01). Compared to baseline, there was a significant within-group changes(improvement) in DTG group, including SF-36 MCS(t=2.16, P=0.04), the subscale of SF-36(t bodily pain=3.56, P<0.01; t vitality=4.84, P<0.01; t mental health=3.96, P<0.01) and PSQI total score(t=-2.36, P=0.03). Changes in SF-36 survey(MCS, bodily pain, vitality, role-emotional and mental health) were significantly correlated with changes in cognitive function(ADAS-Cog, TMT-A and DST-F), especially MCS and ADAS-Cog(r=-0.712, P<0.01), meanwhile, there were significant correlation between changes in PSQI total score(r MMSE=-0.380, P=0.05) and sleep efficiency score(r MMSE=-0.417, PMMSE=0.01; r Mo CA=-0.440, PMo CA=0.03) and cognitive improvements.Conclusions: Findings from this thesis have showed that a 12-week, momentum-based dumbbell training is feasible and effective for improving cognitive functions in older adults with MCI, including global cognitive function, executive function, memory and attention. The evidence also showed the potential benefits of this training for improving motor behavior, quality of life and sleep quality, moreover, these pre-post changes may influence the degree of cognitive benefits induced by dumbbell training. Given the promising results, future studies should evaluate the efficacy of this novel exercise modality in improving specific dimensions of cognitive function and, using a longer follow-up time, examine the sustainability of its training effects. |
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