dbGaP

Search NCBI dbGaP at the study level: the NIH's archive of genotype-and-phenotype studies — the Framingham, MESA, ARIC, CARDIA, Jackson Heart and TOPMed cohorts, trials such as SPRINT and ACCORD, cancer and rare-disease collections — returning each study's accession, design, participant count, institute, diseases, molecular data types (WGS, arrays, RNA-seq), whether reads are in SRA, release date and the controlled-access terms. Use when a question asks which studies hold data on a trait or disease, what a named cohort measured and how many people it enrolled, or where to apply for individual-level data. The study descriptions and variable lists are public; the data itself needs a Data Access Committee application, and the answer should say so.