Study Limitations

REGAIN combines demographic, clinical, electronic health record, digital, and molecular data with a large healthy control cohort. The study's main strength is its regional specificity in Khorasan Razavi adults older than 35 years. The panel’s strengths include a large, continuously maintained nationwide sample and a probability-based design. The study's strengths include streamlined procedures, electronic medical record data, clinic-aligned or home visits, and a large cohort reflecting practice at a small number of sites. The panel reduces bias from volunteer patient samples because participants are selected through random sampling and self-enrolment is not allowed. The study uses a multi-ethnic Malaysian sample, validated questionnaires, blood-based ageing biomarker analysis, and multidimensional ageing assessment. The main strength is integrating machine learning to predict modifiable ageing phenotype and behavioural health factors associated with age acceleration. The multicentre design across six ICUs in five hospitals and multiple US regions supports transferability. The panel’s more than 20-year history enables long-term trend analysis useful for policymaking. Prospective lo…