Comparison between five indices of adherence to the Mediterranean dietary pattern and their association with systemic inflammation and common mental disorders in adults and elderly people living in the city of São Paulo in 2015

Introduction: Adherence to the Mediterranean dietary pattern (MDP) is strongly recognized for its role in the prevention of chronic diseases. The relevance of this dietary pattern, in addition to other functions, has been attributed to its anti-inflammatory performance. A high adherence to the MDP can attenuate inflammatory signaling pathways involving the nervous, endocrine and immune systems, related to the development of mental disorders. In the literature there are different proposals for analysis based on indexes of adherence to the MDP. These proposals differ in terms of their structures and methodologies, and little is investigated about the agreement between them, especially in non-Mediterranean populations. The different available indexes are constructed from different approaches in relation to the population evaluated, which can result in different findings. Objectives: Evaluate and compare five proposals for adherence rates to the MDP; investigate the association between MDP, systemic inflammation and CMD among adults and elderly people living in the city of São Paulo. Methods: Data from the adult and elderly population from the 2015 São Paulo Health Survey (ISA-Capital 2015), a population-based cross-sectional study, were used. The Self Reporting Questionnaire-20 was used to identify the presence of CMD. Adherence to the PDM was assessed using five different dietary indexes (Mediterranean diet scale (MDS), Mediterranean diet Score (MedDietscore), Mediterranean dietary pattern (MDP), Mediterranean Adequacy Index (MAI) and Mediterranean-Style Dietary Pattern Score (MSDPS)), using food consumption data obtained from two 24-hour dietary recalls (R24h). These indexes were subsequently compared regarding the correlation and agreement between their results and the convergent validity of each one was tested using confirmatory factor analysis (CFA). The inflammatory profile was investigated using a Low-Grade Systemic Inflammation Score (LGSI score), constructed based on plasma levels of pro- and anti-inflammatory biomarkers, C-reactive protein (CRP), tumor necrosis factor alpha (TNF-&alpha;), interleukin-10 (IL-10) and adiponectin). Initially, the association between the MDP index with better convergent validity and the inflammatory profile was investigated using linear regression models (adjusted and unadjusted). Next, the direct, indirect and total effects of MDP on CMD were estimated, including systemic inflammation as a mediating variable. A significance level of 5% (p < 0.05) was adopted for the statistical tests (Stata v.14 and Mplus Version 87) Results: Manuscript 1 - The highest correlations were found between the MDP and MAI indexes (r = 076; 95% CI 0.74-0.79) and between MDP and MDS (r = 0.72; 95% CI 0.69-0.75). The greatest agreements observed were moderate, between MDP v. MAI (&kappa; = 0.57, P < 0.001) and MDP v. MDS (&kappa; = 0.48, P < 0.001). The goodness of fit of the model that defined the MedDietscore construct (RMSEA = 0.033, 90% CI 0.02-0.042; SRMR = 0.042) and MSDPS (RMSEA = 0.028, 90% CI 0.019- 0.037; SRMR = 0.031) presented acceptable values for absolute fit indices. Legumes, olive oil, MUFA:SFA ratio and whole grains with legumes were most relevant to characterize the MDP (factor loadings &ge;0&middot;50). Manuscript 2 - Only among the elderly, high adherence to the MDP meant a lower LGSI score of 11.5%. Elderly people classified as having high adherence to the MDP differed consuming less meat and full-fat dairy products. Among the elderly, vegetable and olive oil intake was inversely associated with levels of systemic inflammation. Manuscript 3 - The greatest effect observed in the tested models was the MDP on the LGSI in the elderly. MDP showed direct (SC = -0.247; p = 0.001) and total (SC = -0.315; p<0.001) negative and medium effects on systemic inflammation. MDP also had a small, negative indirect effect on the level of inflammation mediated by BMI (SC = -0.068; p = 0.017). The second largest effect observed was the direct effect (small and negative) of adherence to the PDM on CMD in older adults (SC = -0.182; p = 0.048). The indirect effect of MDP on CMD mediated by the LGSI was not significant (SC = 0.001; p = 0.948). The same result was found in relation to the direct effect of systemic inflammation on CMD (SC = -0.007; p = 0.948). Regarding model fit, the fit indices indicated the good fit of the two models (adults and elderly). Conclusions: The present study showed that following the methodological steps presented, it is possible to identify the Mediterranean indexes that best reflect the objective of evaluating adherence to the Mediterranean diet pattern in a non-Mediterranean population and thus guide the elements of this dietary pattern that can be encouraged to ensure its protective role on mental health and the level of systemic inflammation, especially in the elderly. (AU)