Effect of Physical Exercise on Fluid Intelligence Among the Elderly with or Without Dementia: A Systematic Review of Randomized Control Trials

This review examines the impact of physical exercises on fluid intelligence (FI) among elderly individuals with or without dementia. Fluid intelligence declines with age and worsens faster with dementia, and studies suggest that physical exercise, like aerobic and strength training, may improve fluid intelligence by enhancing neurogenesis, promoting cerebral blood flow, and increasing brain plasticity. A comprehensive search was carried out for studies from inception to 31 May 2024 across databases, including PubMed, Scopus, Web of Science, and PEDro, using keywords related to “physical activity”, “physical exercise”, “fluid intelligence”, and “dementia”. The inclusion criteria focused on randomized control trials (RCTs) involving elderly participants with or without dementia, where fluid intelligence was measured using validated tools. The PEDro scale was used for the quality assessment of included studies. Risk of bias assessment was done using the Cochrane risk of bias tool version 2. Out of 1982 screened studies (PubMed: 104; Web of Science: 1676; Scopus: 195; PEDro: six), five RCTs involving 676 participants were included. Interventions lasted 4 to 24 weeks and included aerobic training, flexibility training, combined strength, and cognitive training, amongst others. It is seen that low- and high-intensity aerobic exercises improved FI, whereas another study reported that combined physical and mental activity significantly enhanced executive function and processing speed. Overall, all included studies demonstrated improvements in FI following exercise interventions. Physical exercises may support fluid intelligence in older adults, but current evidence is limited to a small number of trials. More robust studies are required.