Omega-3 index in the Spanish population older than 60 years: the OMEGAPRED study protocol

The omega-3 index, defined as the sum of the percentages of eicosapentaenoic and docosahexaenoic acids in erythrocytes, is considered a stable biomarker of long-chain omega-3 fatty acid status and is associated with cardiovascular risk, metabolic health, inflammation, and aging-related outcomes. In Spain, the ANIBES study indicated that omega-3 fatty acid intake is insufficient in a significant proportion of the population based on validated dietary questionnaires. However, objective data for establishing the status of omega-3 fatty acids in older adults remain limited. Although fatty acid analysis in erythrocytes is the reference approach for determining the Omega-3 Index, erythrocyte isolation is time-consuming, and less invasive sampling strategies require population-specific validation before they can be used for large-scale nutritional assessment. The OMEGAPRED study aims to characterize omega-3 status in Spanish adults aged 60 years and older and to validate finger-prick-dried blood spot sampling for analyzing the Omega-3 Index using less time-consuming and invasive blood matrices. OMEGAPRED comprises two complementary observational studies. The first is a validation local study of finger-prick-dried blood spot sampling, which included approximately 210 participants in whom venous whole blood samples were collected for fatty acid profiling in whole blood, isolated erythrocytes and finger-prick-dried blood spot. In this cohort, cardiometabolic risk and genetic biomarkers were also measured to explore their clinical association with the Omega-3 Index. The second component is an ongoing national study including approximately 600 participants aged ≥ 60 years, in whom fatty acid profiling is performed using validated finger-prick dried blood spot assay (OmegaQuant ® ). Anthropometric measurements and questionnaires on diet, physical activity, nutritional status, medication use and health and social status were collected from all the participants involved in both studies. Equations derived from the validation local cohort will be applied to estimate erythrocyte omega-3 status at the national level. OMEGAPRED provides an innovative methodological framework for estimating Omega-3 Index from less invasive samples and generates novel biomarker-based information on omega-3 status in older Spanish adults. This approach may support future nutritional screening and prevention-oriented strategies related to cardiometabolic risk and other major outcomes in aging. 11 April 2025 at ClinicalTrials.gov ID NCT06916455.