Brain function effects of exercise interventions for cognitive decline: a systematic review and meta-analysis.

Introduction: Exercise is recognized as a modifiable lifestyle factor that can mitigate cognitive decline and dementia risk. While the benefits of exercise on cognitive aging have been reported on extensively, neuronal effects in adults experiencing cognitive decline have not been systematically synthesized. The aim of this systematic review was to assess the effects of exercise on cognition and brain function in people with cognitive decline associated with dementia risk. Method: A systematic search was conducted for randomized controlled trials of ≥ 4 weeks exercise (aerobic, resistance, or mind-body) that assessed cognition and brain function using neuroimaging and neurophysiological measures in people with subjective or objective cognitive decline. Study characteristics and brain function effects were narratively synthesized, while domain-specific cognitive performance was subjected to meta-analysis. Study quality was also assessed. Results: 5,204 records were identified and 12 unique trials met the eligibility criteria, representing 646 adults classified with cognitive frailty, mild or vascular cognitive impairment. Most interventions involved 40-minute sessions conducted 3 times/week. Exercise improved global cognition (g = -0.417, 95% CI, -0.694 to -0.140, p = 0.003, I2 = 43.56%), executive function (g = -0.391, 95% CI, -0.651 to -0.131, p = 0.003, I2 = 13.28%), but not processing speed or general short-term memory (both p >0.05). Across fMRI and ERP studies, significant neuronal adaptations were found with exercise cf. control throughout the brain and were linked with improved global cognition, memory, and executive function. Cerebral blood flow was also found to improve with 24 weeks of exercise, but was not linked with cognitive changes. Discussion: The cognitive improvements associated with exercise are likely driven by increased metabolic activity, cerebrovascular mechanisms, and neuroplasticity throughout the brain. Our paper shows the promise in, and need for, high-quality trials integrating cognitive and brain function measures to elucidate the functional relationship between exercise and brain health in populations with a high risk of dementia. Systematic review registration: PROSPERO, identifier: CRD42022291843.

Computerized Cognitive Training in Multiple Sclerosis: A Systematic Review and Meta-analysis.

Background. Cognitive impairments are common in people with multiple sclerosis (MS). Systematic reviews reported promising evidence for various cognitive interventions in this population. Computerized cognitive training (CCT) has strong evidence for safety and efficacy in several populations, but its effects in MS have yet to be specified. Objective. We aimed to synthesize the evidence from randomized controlled trials (RCTs) investigating the effects of CCT on cognitive, psychosocial, and functional outcomes in adults with MS. Method. We searched MEDLINE, EMBASE, PsycINFO, CINAHL, and CENTRAL from inception to March 2019. We calculated standardized mean difference (Hedges' g) of change from baseline in untrained measures of cognition, individual domains, psychosocial functioning, and daily function between CCT and control groups using a random-effects model. Results. A total of 20 RCTs encompassing 982 participants (78% with relapsing-remitting MS) were included. The overall cognitive effect size was moderate (g = 0.30; 95% CI = 0.18-0.43), with no evidence of small-study effect or between-study heterogeneity (prediction interval = 0.17-0.44). Small to moderate effect sizes were found for attention/processing speed, executive functions, and verbal and visuospatial memory. Evidence for working memory, fatigue, and psychosocial and daily functioning were inconclusive. Cognitive effects waned without further training. Conclusions. CCT is efficacious for overall and key cognitive domains in adults with MS, but efficacy on other outcomes and in progressive subtypes remains unclear. Long-term and well-powered trials with diverse cohorts are needed to optimize and maintain the efficacy of CCT, investigate transfer to daily living, and determine who can benefit and whether CCT is a cost-effective strategy to attenuate cognitive decline in MS.

Cognitive training in Parkinson disease: A systematic review and meta-analysis.

OBJECTIVE: To quantify the effects of cognitive training (CT) on cognitive and behavioral outcome measures in patients with Parkinson disease (PD). METHODS: We systematically searched 5 databases for randomized controlled trials (RCTs) of CT in patients with PD reporting cognitive or behavioral outcomes. Efficacy was measured as standardized mean difference (Hedges g) of post-training change. RESULTS: Seven studies encompassing 272 patients with Hoehn & Yahr Stages 1-3 were included. The overall effect of CT over and above control conditions was small but statistically significant (7 studies: g = 0.23, 95% confidence interval [CI] 0.014-0.44, p = 0.037). True heterogeneity across studies was low (I(2) = 0%) and there was no evidence of publication bias. Larger effect sizes were noted on working memory (4 studies: g = 0.74, CI 0.32-1.17, p = 0.001), processing speed (4 studies: g = 0.31, CI 0.01-0.61, p = 0.04), and executive function (5 studies: g = 0.30, CI 0.01-0.58, p = 0.042), while effects on measures of global cognition (4 studies), memory (5 studies), visuospatial skills (4 studies), and depression (5 studies), as well as attention, quality of life, and instrumental activities of daily living (3 studies each), were not statistically significant. No adverse events were reported. CONCLUSIONS: Though still small, the current body of RCT evidence indicates that CT is safe and modestly effective on cognition in patients with mild to moderate PD. Larger RCTs are necessary to examine the utility of CT for secondary prevention of cognitive decline in this population.