Dietary Inflammatory Index and Cognitive Function: Findings from a Cross-Sectional Study in Obese Chinese Township Population from 45 to 75 Years

Abstract

Background and objective: Cognitive dysfunction is highly prevalent in obese people, and food is a key factor in obesity, and dietary inflammatory index (DII) can reflect whether diet has anti-inflammatory or pro-inflammatory potential. In addition, dietary fatty acid consumption is linked to inflammation, obesity, and cognitive impairment. Erythrocyte membrane fatty acids can reflect dietary fatty acid intake. Our hypothesis was that erythrocyte membrane fatty acids might have a significant impact on the relationship between DII and cognition in obese individuals, and we designed experiments to test the hypothesis.

Methods: In three villages in Beijing, we collected 579 respondents from individuals 45 to 75 years old and categorized them by body mass index. The Montreal Cognitive Assessment (MoCA) score and DII score was calculated and gas chromatography was used to measure the proportion of erythrocyte membrane fatty acids. The relationship between the DII score and cognition was examined using multiple linear regression and binary logistic regression. Mediation analysis can help to understand the causal chain between variables, deeply explore the internal relationship and mechanism of action between variables. So a multiple chain mediation model was developed to investigate the mediating factors between the DII score and cognitive association.

Results: According to adjusted linear regression, higher DII scores were linked to lower MoCA scores in the obese group. The negative correlation between DII score and cognitive function score remains in binary linear regression. We discovered through mediation analysis that erythrocyte membrane fatty acids mediate the detrimental link between DII and cognitive function in obese individuals.

Conclusion: We propose that higher DII scores in obese people are associated with a decline in cognitive function. In addition, this effect might be mediated via the fatty acids in the erythrocyte membrane.

Keywords: chain mediation effect; dietary inflammatory index; fatty acids; mild cognitive impairment; obesity.

Figure 1

Study flowchart.

Figure 2

Schematic Diagram of Multiple Chain Mediation Effect Model. (X) Independent variable; (Y) Dependent variable; M1: Mediator 1; M2: Mediator 2; a1: Effect coefficient of X on M1; a2: Effect coefficient of X on M2; b1: Effect coefficient of M1 on Y; b2: Effect coefficient of M2 on Y; c’: Effect coefficient of X on Y.

Figure 3

The proportions of DII tertiles in NM and OB groups. Univariate analysis was carried out using the chi-square test.

Figure 4

Comparison of food compositions and the DII scores in NM and OB group. Data were tested for normality and comparisons between groups were performed using the Mann–Whitney U-test *P<0.05.

Figure 5

Forest plot of binary logistic analysis of the association between Dietary inflammatory index and MoCA scores in normal participants. Tertiel 1(◆), Tertiel 2(●), Tertiel 3(■). (A): the association between DII and MoCA scores in NM group; (B): the association between DII and MoCA scores in OB group. 95% CI: 95% Confidence interval; **P<0.01, *P<0.05. Model 1: adjusted for age, gender, waist-Hip ratio, energy intake, culture. Model 2: adjusted for the variables in Model 1 plus lifestyle (smoking, drinking and exercise). Model 3: adjusted for the variables in Model 2 plus disease (history of hypertension, diabetes mellitus, hypertriglyceridemia).