The associations of energy adjusted dietary inflammatory index with brain structure and cognitive function

Limited research exists on the mediating effect of brain structure in the association between dietary inflammatory index (DII) and cognitive impairment. To address this issue, this analysis utilized data from a cohort of 15,526 participants in the UK Biobank who underwent brain magnetic resonance imaging (MRI) during 2014-2020. We assessed the associations between energy adjusted DII (E-DII, calculated by 28 components) and cognitive function (represented by fluid intelligence scores, FIS), as well as the brain structures, including total brain volume (TBV), white matter volume (WMV), white matter hyperintensities volume (WMHV) and grey matter volume (GMV) of 76 cortices, 14 subcortices and 28 cerebellum regions. We further estimated the mediation effects of brain structures on the association between E-DII and cognitive function. From this analysis, we observed that higher E-DII was associated with reduced TBV, GMV, WMV, FIS and higher WMHV. Each one unit increase in E-DII was associated with 0.025(0.007, 0.041) FIS decrease, 937.93 mm3 (95% CI: 494.48.07, 1,381.38) GMV decrease, 675.02 mm3 (95% CI: 279.02, 1,071.02) WMV decrease and 93.80 mm3 (95% CI: 41.45, 146.14) WMHV increase. Furthermore, GMV, WMHV, WMV were found to significantly mediate the association between E-DII and cognitive function, accounting for 21.82% (95% CI: 11.26%, 33.24%), 19.19% (95% CI: 8.52%, 30.63%) and 4% (95% CI: 1.31%, 7.99%). These results indicated that controlling of inflammatory diet could prevent brain structures abnormalities and might reduce the risk of cognitive impairment.