Biobank and Brain Health in Bordeaux.

Cognitive aging and associated pathologies, primarily dementia and its main cause Alzheimer's disease, are a major public health issue. Because of the under-diagnosis of dementia in the population and the very long preclinical phase of these diseases, population-based cohorts are essential to better understand brain aging. With the PAQUID and 3-Cités cohorts, the Bordeaux Population Health Research Center (BPH) has been a world pioneer in population-based studies on aging and dementia, and has thus contributed greatly to a better understanding of age-realted brain diseases. As these cohorts are aging, and in view of the importance of studying the early stages of brain aging, it seems essential to continue our research efforts for the prevention of cognitive aging with the establishment of a new cohort of young seniors. In addition to the population-based design of the study, the representativeness of the cohort appears to be a crucial issue (since population-based cohorts depend on the voluntary participation of healthy individuals, unfavorable exposures and altered health states are often largely under-represented, which reduces the variability of exposures and events, leading to an underestimation of prevalences, a decrease in statistical power and a potential bias in the estimation of associations). Finally, the multifactorial nature of brain ageing pathologies now calls for the replacement of the reductionist approach of risk factors by a more holistic vision of the exposome (defined as all the environmental exposures with which an individual is confronted throughout the lifecourse). The development of an integrated approach of complex, high-dimensional, multi-omics biological data (genomics, transcriptomics, epigenomics, metabolomics, proteomics), applied to various biological matrices, is an indispensable tool to deep phenotyping and to the establishment of a new generation etiological epidemiological research framework in the field of brain aging pathologies. The Biobank and Brain health in Bordeaux cohort (B cube) will include the completion of a general questionnaire (during the V1 visit), a dietary survey (during the V1, V4 and V5 visits), a computerized cognitive battery (during the V1 visit), a collection of biological material (blood, urine, stool, saliva, hair, nails and nasopharyngeal swab) for the constitution of a biobank (during the V2 biobank visit, 2000 samples of blood, urine, hair, nails and 1000 samples expected for the other fluids/samples) An MRI will be performed in volunteers aged 55 to 70 years (during the V3 visit). Finally, a complementary visit by a medical specialist may be proposed to participants with cognitive disorders or Parkinson's syndrome. Approximately three years after V1, a follow-up phase is proposed to the participant, comprising a block of 6 visits: a general questionnaire accompanied by a computerized cognitive battery (V7), a dietary survey (V7, V9, V10 and V11), a new collection of biological material (V8) including blood samples and hair (for all participants in the follow-up phase) and stool samples (if sampling had not taken place during V2 and for a subsample of participants at follow-up).