Mediterranean diet and dementia: MRI marker evidence from meta-analysis.

Background: Dementia is a growing public health concern with limited effective treatments. Diet may be a modifiable factor that significantly impacts brain health. Mediterranean diet (MeDi) has been suggested to be associated with brain Magnetic Resonance Imaging (MRI) markers related to dementia, but the existing evidence is inconsistent.

Objectives: This systematic review and meta-analysis aimed to quantify the association between MeDi and dementia-related MRI markers.

Methods: A systematic search was conducted on PubMed, Embase, and Web of Science up to September 2024. Two reviewers worked in parallel to select studies and extract data. We considered epidemiologic studies that reported beta coefficients (β) with 95% confidence intervals (CIs) for MRI markers related to MeDi. Separate meta-analyses were performed for cross-sectional and longitudinal studies.

Results: A total of 20 relevant studies involving 44,893 individuals were included in the analysis. Thirteen cross-sectional studies included a total of 42,955 participants. A meta-analysis of cross-sectional studies revealed significant associations between MeDi and white matter hyperintensity (WMH) (β = - 0.03, 95% CI = - 0.05- - 0.01, P = 0.02). However, there were no significant associations found between MeDi and total brain volume (TBV) (β = - 0.03, 95% CI = - 0.20-0.13, P = 0.71), gray matter volume (GMV) (β = 0.26, 95% CI = - 0.19-0.71, P = 0.26), white matter volume (WMV) (β = - 0.09, 95% CI = - 0.40-0.22, P = 0.58), or hippocampal volume (HCV) (β = - 1.02, 95% CI = - 7.74-9.79, P = 0.82). In the longitudinal analysis, seven prospective studies with an average follow-up period ranging from 1.5 to 9 years and involving 1,938 participants. The combined effect size of MeDi showed no significant association with TBV or GMV.

Conclusion: Adherence to MeDi may be associated with reduced WMH in older adults. This suggests that MeDi may affect brain health and highlights the need for further research into its role as a modifiable lifestyle factor that might potentially modify the risk of dementia.