UKB data map

Field ID placeholders (verify in extract): - Age: 21022 / 21003 - Sex: 31 - Income: 738 - Assessment center / site: 21054 or 54 - Genetics PCs: 22009 (pcs_1..10) - Imaging-derived phenotypes + confounds: FMRIB tables

Note: Instances follow UKB suffixes (e.g., -0.0 baseline vs -2.0 repeat imaging). Capture instance + visit metadata in schemas.