Background and objectives: High adherence to the Mediterranean diet (MeDi) has been associated with slower age-dependent cognitive decline and better cardiovascular health (CVH). We examined the association between adherence to MeDi and white matter (WM) integrity in community-dwelling Hispanic or Latino adults. In secondary analysis, we assessed whether CVH and WM integrity were pathway variables between MeDi and global cognition (GC).
Methods: Data from Study of Latinos-Investigation of Neurocognitive Aging-MRI Ancillary Study were analyzed. Dietary intake was collected during the baseline visit (2008-2011) using 24-hour recalls, from which a MeDi score ([MeDiS], range 0-9) was derived. Brain MRI scans with diffusion tensor imaging were obtained between 2017 and 2022. WM integrity was assessed using total WM volume (tWM), WM hyperintensity (WMH) volume, fractional anisotropy (FA), and free water (FW). GC was ascertained between 2015 and 2018 using a composite score derived from 4 standardized cognitive tests. CVH was evaluated at baseline using the Life's Essential 7 score ([LE7], range 0-100), a modified version of the existing Life's Essential 8 score, in which diet was excluded to avoid collinearity with our exposure. We used linear regression models that controlled for age, sex, and socioeconomic factors to investigate the association of MeDiS with WM integrity. We performed mediation analysis to explore whether CVH and WM integrity were pathway variables between diet and GC.
Results: A total of 2,642 participants with a mean age of 64.3 years (95% CI 63.4-65.1, 44% male) were included. The average MeDiS was 5.0 (95% CI 4.9 to 5.1), and the LE7 score was 66.6 (95% CI 65.-67.6). Higher MeDiS was associated with lower WMH volume (β = -0.08, 95% CI -0.11 to -0.04), higher tWM volume (β = 0.05, 95% CI 0.005-0.09), lower FW (β = -0.04, 95% CI -0.08 to -0.002), and higher fractional anisotropy (FA) (β = 0.09, 95% CI 0.05-0.13). WMH, tWM, and FA mediated the association between MeDiS and GC. In addition, there was serial mediation from MeDiS on GC through LE7 score, WMH, tWM, and FA.
Discussion: Higher adherence to MeDi is linked to better WM structural integrity, which, together with CVH, mediates the association between MeDi and GC.