| Summary: | Background Dietary quality indices (DQI) are widely used in nutritional epidemiology.
However, how they might change over time in a Mediterranean population is not well
understood. Objective To evaluate within-participant longitudinal changes in scores for nine a prioriedefined DQIs: Fat Quality Index (FQI), Carbohydrate Quality Index (CQI), Provegetarian Dietary Pattern (PVG), Mediterranean Diet Adherence Screener (MEDAS), Mediterranean Diet Score (MDS), Dietary Approaches to Stop Hypertension (DASH), Mediterranean-DASH Intervention for Neurodegenerative Delay Diet (MIND), Prime Diet Quality Score (PDQS) and Alternate Healthy Eating Index (AHEI-2010) in the “Seguimiento Universidad de Navarra” (SUN) cohort, a well-known Mediterranean cohort of university graduates, and to identify baseline predictors of improvement in MEDAS and AHEI-2010 after 10 years of follow-up. Design In this longitudinal cohort study, DQI scores were calculated based on responses from a validated semiquantitative food-frequency questionnaire (FFQ). Participants/setting Spanish university graduates enrolled in the SUN cohort before March 2008, who completed the 10-year FFQ and reported total dietary intake at baseline and after 10 years of follow-up, included 2,244 men and 3,271 women, whose mean age at baseline was 36.3 years (standard deviation [SD], 10.7). Main outcome measures Main outcome measures were within-participant longitudinal changes for FQI, CQI, PVG, MEDAS, MDS, DASH, MIND, PDQS, and AHEI-2010. Statistical analyses performed Adjusted logistic regression models were used to evaluate within-participant longitudinal changes and to identify baseline predictors of improvements 10% in MEDAS and AHEI-2010 scores after 10 years of follow-up.
Results The comparison of the nine scores of DQI calculated at baseline and after 10 years of follow-up showed an improvement in all DQI scores except for PDQS. The greatest changes in DQIs were found for MEDAS (from 6.2 to 7.2, þ22.9%) and MDS (from 4.3 to 4.4, þ15.4%). The strongest predictors at baseline for 10% improvements in MEDAS or AHEI-2010 scores varied across indices. Being female, 35 years old, and more physically active at baseline were associated with improvement, whereas snacking between meals was associated with <10% improvements in both indices.
Conclusions In this cohort, the changes in nine a priori-defined DQI scores suggested modest improvements in diet quality, in which MEDAS and MDS scores showed the largest improvements. Additional longitudinal studies, especially intervention trials with long follow-up, are warranted to establish the most appropriate DQIs to assess long-term changes in diet quality in adult populations.
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