Does a combined intervention of diet and exercise lead to a more positive impact on neurocognitive function? A systematic review and meta-analysis.

Background: Recent studies have shown that lifestyle modifications, including diet and exercise, can help prevent cognitive decline. However, there are currently no comprehensive systematic reviews of the combined effects of diet and exercise on cognitive function.

Methods: A systematic review of the literature identified randomized controlled trials that examined the effects of combined diet and exercise interventions on neurocognitive function compared with either intervention alone. The following databases were searched: PubMed, Web of Science, Embase, and Google Scholar. The search was conducted up until October 13, 2024. A meta-analysis was conducted using a random-effects model, and the quality of the evidence was evaluated using the GRADE approach.

Results: A total of 11 randomized controlled trials were subjected to analysis, comprising a total of 3428 participants. The combined diet and exercise intervention was found to significantly improve global cognitive function scores (SMD = 0.32, 95% CI 0.15 to 0.49, I = 0%), memory function (SMD = 0.29, 95% CI 0.16 to 0.41, I = 17%, p = 0.29), and executive function (SMD = 0.52, 95% CI 0.31 to 0.72, I = 52%) in moderate-quality results. Results of subgroup analyses showed that, compared with diet or exercise alone, the combined intervention did not show a statistically significant improvement in global cognitive function. Compared with cognitively healthy individuals(SMD = 0.10, 95% CI 0.02 to 0.17, I = 0%), the combined intervention was more effective in improving global cognitive function in individuals at risk for cognitive decline(SMD = 0.76, 95% CI 0.47 to 1.04, I = 71%). Among the dietary interventions in the combined intervention, supervised dietary intervention(SDI)(SMD = 0.10, 95% CI 0.02 to 0.17, I = 0%) and the Dietary Approaches to stop Hypertension diet(DASH)(SMD = 0.77, 95% CI 0.51 to 1.03, I = 65%) showed positive effects on improving global cognitive function. In terms of executive function improvement, the results showed that the combined intervention had positive effects on the Stroop color and word test(SCWT)(SMD = 0.39, 95% CI 0.17 to 0.60, I = 0%) and the Trail Making Test(SMD = 0.63, 95% CI 0.26 to 1.00, I = 76%).

Conclusion: The combined strategy of diet and exercise positively affects neurocognitive function, including overall cognitive function, memory, and executive function. However, no significant differences were found between the effects of combined interventions and single interventions on overall cognitive function.