In a recent study published in the journal Frontiers of nutritionresearchers developed a method to retrospectively reconcile data on the association between dietary patterns and cognitive health from individual studies with widely varying methodologies and results.

Review: Dietary patterns associated with cognitive decline: How to reconcile data from European and US cohort studies. Image credit: Elena Eryomenko / Shutterstock

background

A growing area of ​​research is the association between dietary patterns and cognitive health, particularly with regard to understanding modifiable risk factors for dementia and other neurodegenerative diseases. Results from various reviews and meta-analyses indicate that diets rich in fruits, whole grains, and vegetables are beneficial for cognitive health.

However, results from individual studies on dietary patterns such as Dietary Approaches to Stop Hypertension (DASH), Mediterranean, Anti-Inflammatory Diet, Mediterranean DASH Diet, and Delayed Intervention for Neurodegeneration (MIND) Diet are inconsistent. These discrepancies, due to the heterogeneity of methods of conducting dietary and cognitive assessments, study populations, follow-up periods, and various other study parameters, make it difficult to conclude potential dietary guidelines for cognitive health. is becoming difficult.

Proposed approaches to draw inferences from these heterogeneous individual studies include pooling individual participant data from different clinical and observational trials, as well as meta-analyses. It differs from a meta-analysis in that data is retrieved from eligible studies rather than extracted from publications. However, ways to harmonize data are still needed to ensure comparability and compatibility across the data.

About research

This study described a protocol to retrospectively harmonize individual participant data from numerous US and European studies on the association between dietary patterns and cognitive health. They also discussed study selection criteria to address the research questions and provided study results and definitions of exposure.

data harmonization

In order to determine the association between dietary patterns and the incidence of cognitive decline and mild cognitive impairment, inclusion criteria included study designs that were either clinical trials or clinical trials, representative of diverse populations in the United States and Europe. It was specified that studies that investigated diet should be included. Prospective cohort study. The harmonization analysis included only studies conducted with cognitively healthy adults aged 35 and older. Sensitivity analyzes were recommended to assess the interaction effects of comorbidities such as obesity, cardiovascular disease, diabetes, depression, and physical activity.

Exposures considered in the analysis include dietary patterns such as the Mediterranean Diet Pattern, the EAT-Lancet Pattern, the Healthy Eating Index, or adaptations of derived patterns. in the aftermath From the results of principal component analysis. Data from dietary history, food frequency questionnaires, or repeated interviews are used to determine a daily dietary intake score.

The results of the analysis consist of cognitive performance assessments at two time points to determine cognitive changes or the onset of mild cognitive impairment. Data on dietary patterns are harmonized into food and beverage groups such as dairy, vegetables, fruit, meat, candy, and sugar-sweetened beverages.

The researchers also recommended that the units used convert the nutrients to 1 unit and report them along with the number of grams per serving of each food category. Harmonized dietary data consist of one exposure variable of healthy eating patterns and are reported in scores such as the Healthy Eating Index.

The proposed method for harmonizing individual participant data ensures that only cognitive measures that can diagnose mild cognitive impairment or measure executive function, verbal fluency, or verbal memory are included in the analysis. It was suggested. Additionally, cognitive data should be harmonized using a priori statistical harmonization in order to classify each study’s cognitive tests according to the cognitive abilities investigated.

A schematic study protocol to assess the association between dietary patterns and cognitive decline.

Data augmentation strategies were proposed to address possible heterogeneity across factors such as administration of cognitive measures, instrument adaptation, components, and instrument versions. Additionally, confirmatory factor analysis is used to test the equivalence of cognitive measures.

The study also discussed how to harmonize data on confounding factors such as lifestyle, physical activity, sociodemographic factors, anthropometry, and physical activity levels. Harmonized data on dietary intake, cognitive indicators, and confounders will be used to determine associations between diet and cognitive health through meta-analysis of individual participant data.

conclusion

In summary, this study provides a way to harmonize data from numerous disparate studies so that study designs can infer associations between dietary patterns and cognitive health. Application of this method and its results will help develop dietary recommendations to improve cognitive health and prevent cognitive decline.