Effect of long-term physical exercise and multidomain interventions on cognitive function and the risk of mild cognitive impairment and dementia in older adults: A systematic review with meta-analysis.

Introduction: Recent studies have suggested that sustained multidomain interventions, including physical exercise, may be beneficial in preventing cognitive decline. This review aims to assess the impact of prolonged physical exercise and multidomain strategies on overall cognitive faculties and dementia risk among community-dwelling older adults without dementia.

Methods: We systematically searched PubMed, Web of Science, PsychInfo, and CINHAL databases from inception until April 1, 2024, for randomized controlled trials that investigated the effects of long-term (≥ 12 months) physical exercise or multidomain interventions on non-demented, community-dwelling older adults. The primary outcomes assessed were changes in global cognition and the risk of mild cognitive impairment (MCI) or dementia. Standardized mean differences (SMD) and risk ratios (RR) with 95 % confidence intervals were computed using a random-effects inverse-variance method with the Hartung-Knapp-Sidik-Jonkman adjustment for effect size calculation. The Cochrane Risk-of-Bias-2 tool (RoB-2) was used for bias assessment, and the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) approach was applied to evaluate the certainty of evidence.

Results: Sixteen trials, including 11,402 participants (mean age 73.2 [±5.5] years; 62.3 % female) were examined. The risk of bias was low. Moderate-certainty evidence indicated that physical exercise interventions had modest to no effect on cognitive function (k= 9, SMD: 0.05; 95 % CI: -0.04-0.13; p = 0.25), whereas multidomain interventions were significantly impactful (k=7, SMD: 0.09; 95 % CI: 0.04-0.15; p < 0.01). Physical exercise interventions did not alter MCI risk (k= 4, RR: 0.98; 95 % CI: 0.73-1.31; p = 0.79) or dementia onset (k= 4, RR: 0.61; 95 % CI: 0.25-1.52; p = 0.19), with very low-to low-certainty evidence, respectively.

Conclusions: Integrative multidomain strategies incorporating physical exercise may benefit the global cognitive function of older adults. However, long-term physical exercise alone did not yield any cognitive gains. The effectiveness of such exercise interventions to mitigate the overall risk of incident MCI and dementia warrants further research.