Single-factor NHANES findings: a third replicated in new data, most tests lacked power, and most analyses differ from their description

Many papers relate one NHANES variable to one health condition without correcting for multiple testing (Suchak et al. (2025)). We sampled 40 of their associations, reproduced each on its paper's cycles, and, under a registered plan, re-ran it on August 2021–August 2023. There, 14 replicated; most tests lacked power, but of the 13 that had it, 10 replicated. Effects were a median 0.765 times their published size, and 3 differed significantly from it. In 36 papers the computation that reproduces the published estimate differs from the paper's description, as the paper itself shows in and recomputation in more. Their methods sections poorly describe what their estimates measure, and one cycle can test few of the associations.