Reshaping the path of mild cognitive impairment by refining exercise prescription: a study protocol of a randomized controlled trial to understand the "what," "for whom," and "how" of exercise to promote cognitive function.

BACKGROUND: Targeted exercise training is a promising strategy for promoting cognitive function and preventing dementia in older age. Despite the utility of exercise as an intervention, variation still exists in exercise-induced cognitive gains and questions remain regarding the type of training (i.e., what), as well as moderators (i.e., for whom) and mechanisms (i.e., how) of benefit. Both aerobic training (AT) and resistance training (RT) enhance cognitive function in older adults without cognitive impairment; however, the vast majority of trials have focused exclusively on AT. Thus, more research is needed on RT, as well as on the combination of AT and RT, in older adults with mild cognitive impairment (MCI), a prodromal stage of dementia. Therefore, we aim to conduct a 6-month, 2 × 2 factorial randomized controlled trial in older adults with MCI to assess the individual effects of AT and RT, and the combined effect of AT and RT on cognitive function and to determine the possible underlying biological mechanisms. METHODS: Two hundred and sixteen community-dwelling adults, aged 65 to 85 years, with MCI from metropolitan Vancouver will be recruited to participate in this study. Randomization will be stratified by biological sex and participants will be randomly allocated to one of the four experimental groups: (1) 4×/week balance and tone (BAT; i.e., active control); (2) combined 2×/week AT + 2×/week RT; (3) 2×/week AT + 2×/week BAT; or (4) 2×/week RT + 2×/week BAT. The primary outcome is cognitive function as measured by the Alzheimer's Disease Assessment Scale-Cognitive-Plus. Secondary outcomes include cognitive function, health-related quality of life, physical function, actigraphy measures, questionnaires, and falls. Outcomes will be measured at baseline, 6 months (i.e., trial completion), and 18 months (i.e., 12-month follow-up). DISCUSSION: Establishing the efficacy of different types and combinations of exercise training to minimize cognitive decline will advance our ability to prescribe exercise as "medicine" to treat MCI and delay the onset and progression of dementia. This trial is extremely timely as cognitive impairment and dementia pose a growing threat to global public health. TRIAL REGISTRATION: ClinicalTrials.gov NCT02737878 . Registered on April 14, 2016.

Effects of exercise training on the cognitive function of older adults with different types of dementia: a systematic review and meta-analysis.

OBJECTIVES: To assess the effect of exercise training on the cognitive function of older adults living with different types of dementia, as well as potential moderators of exercise efficacy. DESIGN: Systematic review and meta-analysis. DATA SOURCES: Cochrane Central, PsycINFO, Embase, Medline and CINAHL. ELIGIBILITY CRITERIA: Peer-reviewed, randomised controlled trials, in English (1990-present), which examined the effects of exercise training on the cognitive function of older adults living with dementia. STUDY APPRAISAL AND SYNTHESIS: Risk of bias and study quality were assessed (Cochrane Risk of Bias Tool 2.0 and Physiotherapy Evidence Database Scale). We performed random-effects models using robust variance estimation and tested moderators using the approximate Hotelling-Zhang test. RESULTS: Twenty-eight studies (n=2158) were included in the qualitative review and 25 in the meta-analysis. For all-cause dementia, a small effect of exercise training on cognitive function was observed (g=0.19; 95% CI 0.05 to 0.33; p=0.009). Type of dementia and exercise training characteristics did not moderate the effects of exercise training on cognitive function (p>0.05). Adherence to the intervention moderated the cognitive outcome effect size such that greater mean adherence was associated with greater cognitive outcome effect sizes (b=0.02; SE=0.01; p=0.005). CONCLUSION: Exercise training showed small benefits for the cognitive function of older adults living with all-cause dementia. More research and standardised reporting of exercise training characteristics can strengthen the evidence for what works best for which types of dementia. PROSPERO REGISTRATION NUMBER: CRD42020198716.

Optimizing Sleep in Older Adults: Where Does High-Intensity Interval Training Fit?

The present community-based study evaluated the effect of three different exercise interventions on sleep quality. Older adults were enrolled in one of three exercise intervention groups: high-intensity interval training (HIIT; n = 20), moderate-intensity continuous training (MICT; n = 19) or stretching (STRETCH; n = 22). Prior to and following the intervention, sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). The PSQI was used to classify participants as poor (global PSQI score ≥5) or good (global PSQI score >5) sleepers and the effect of the intervention was examined on poor sleepers only. Around 70% of our sample was classified as poor sleepers. Poor sleepers were significantly impaired across all PSQI components, except for the use of sleeping medication, such that neither group was heavily prescribed. Exercise improved sleep quality for poor sleepers, but the intensity mattered. Specifically, MICT and STRETCH improved sleep efficiency for poor sleepers, whereas HIIT did not (p < 0.05). The results suggest that both MICT and STRETCH may be more effective than HIIT for optimizing sleep in poor sleepers. These findings help to inform exercise guidelines for enhancing sleep in the aging population.

The Association of Aging and Aerobic Fitness With Memory.

The present study examined the differential effects of aging and fitness on memory. Ninety-five young adults (YA) and 81 older adults (OA) performed the Mnemonic Similarity Task (MST) to assess high-interference memory and general recognition memory. Age-related differences in high-interference memory were observed across the lifespan, with performance progressively worsening from young to old. In contrast, age-related differences in general recognition memory were not observed until after 60 years of age. Furthermore, OA with higher aerobic fitness had better high-interference memory, suggesting that exercise may be an important lifestyle factor influencing this aspect of memory. Overall, these findings suggest different trajectories of decline for high-interference and general recognition memory, with a selective role for physical activity in promoting high-interference memory.