In Switzerland by 2045, we expect 2.7 Mio citizens aged 65+ of whom 1.0 Mio. aged 80+. A priority and focus of personalized health research is therefore aging biology to extend healthy life expectancy. Novel molecular and imaging features will emerge as candidate targets for risk prediction and screening of chronic diseases. It is of utmost importance to test the clinical and public health utility of candidate biomarkers evolving from this research in citizen reference cohorts. We will build a Swiss Aging Citizen Reference (SACR), a testable and scalable reference cohort offering interoperable, searchable, and accessible data. 1000 participants from existing Swiss citizen cohorts will be combined and analyzed for DNA methylation and MRI brain imaging. SACR will serve as a testbed for clinical and public health utility of candidate biomarkers. As for a proof-of-concept study, we will conduct an agnostic search for structural and functional brain features associated with epigenetic aging acceleration to examine the potential of epigenetic age acceleration as the intermediate aging biomarker and to better understand the aging mechanism in brain.