The more the better? A meta-analysis on effects of combined cognitive and physical intervention on cognition in healthy older adults

Both cognitive intervention and physical exercise benefit cognitive function in older adults. It has been suggested that combined cognitive and physical intervention may induce larger effects than cognitive or physical intervention alone, but existing literature has shown mixed results. This meta-analysis aimed at assessing the efficacy of combined intervention on cognition by comparing combined intervention to control group, cognitive intervention and physical exercise. Eligible studies were controlled trials examining the effects of combined intervention on cognition in older adults without known cognitive impairment. Twenty interventional studies comprising 2667 participants were included. Results showed that the overall effect size for combined intervention versus control group was 0.29 (random effects model, p = 0.001). Compared to physical exercise, combined intervention produced greater effects on overall effect size (0.22, p < 0.01), while no significant difference was found between combined intervention and cognitive intervention. Effects of combined intervention were moderated by age of participants, intervention frequency and setting. The findings suggest that combined intervention demonstrates advantages over control group and physical exercise, while evidence is still lacking for superiority when compared combined intervention to cognitive intervention. More well-designed studies with long follow-ups are needed to clarify the potential unique efficacy of combined intervention for older adults.