EFFECT OF EXERCISE ON COGNITIVE FUNCTION IN PERSONS WITH DEMENTIA: A SYSTEMATIC REVIEW AND META-ANALYSIS

As the population ages, the number of people suffering from dementia will rise significantly. Current estimates of total societal cost of dementia exceed $8 billion dollars (US). Epidemiological studies have shown that increased lifetime engagement in exercise reduces cognitive decline and the incidence of dementia in normal older adults. While existing research suggests that lifelong exercise may be preferable, the adoption of exercise at any age and stage of dementia-onset to delay or reverse cognitive decline is worthwhile given the prevalence of sedentary lifestyle, and the increasing proportion of older adults and dementia incidence. Recently, trials have started to explore the impact of exercise on cognitive symptoms in individuals diagnosed with dementia. These studies are reporting promising findings, which call for further meta-analytical review. The primary objective of this meta-analysis is to examine the effects of exercise interventions on cognitive function compared to standard care in older persons with dementia. The secondary objectives are to identify covariates and/or moderators that affect the effectiveness of these exercise programs. The trials included in this meta-analytic review were identified from systematic searches of major medical and psychological databases, including EMBASE, PubMed/MEDLINE, PsycARTICLES, and Cochrane Central Register of Controlled Trials (1966-2018) on 30 April 2018 using the concepts of dementia, cognitive function, and exercise. Trials were selected in which older people, diagnosed with dementia, were allocated either to exercise programs or to control groups (standard care) with the aim of improving cognition. One rater retrieved the articles, assessed for inclusion and methodological quality, and extracted the data. Data was analyzed for summary effects using mean difference (MD) and standardized mean difference (SMD). Data was synthesized for each outcome using a random-effects model. Exploration of heterogeneity was planned in relation to type, frequency and duration of exercise program. The collected data were analyzed by Review Manager (5.3). This review evaluated the results of 21 trials, including 1548 participants, that tested whether exercise programs could improve cognition (which includes such things as memory, learning, attention) in older people with dementia. The included trials were heterogeneous in terms of participant characteristics, and type, duration, and frequency of exercise. Meta-analysis demonstrated positive effects of exercise on cognitive function in older adults with dementia (SMD = 0.49, 95% CI [0.24 - 0.75], P = 0.0002). Fifteen trials demonstrated that exercise improves cognitive function for individuals with dementia, while the remaining six studies did not display a beneficial effect of exercise on cognitive function. This analysis revealed substantial heterogeneity (I2 = 79%), most of which could not be explained, and the quality of evidence was rated as low. Thus, findings should be interpreted with caution. This meta-analysis and systematic review revealed some evidence supporting the benefit of exercise programs in improving cognitive ability or slowing the decline of cognition in people with dementia. Future well-designed RCTs with clear intervention criteria, large samples, and long-term follow-up are needed to enhance the quality of such a review by assessing the exercise programs that are best for people with various types and severity of dementia and by addressing additional outcomes (e.g., mortality, quality of life, healthcare service use, expenditures)