Withings HFRN Retrospective Study

Inclusion Criteria: * Users of commercially purchased, consumer-grade Withings smart scales * A source of step counts synced into the Withings ecosystem (a Withings activity tracker, a smartphone, or a third-party activity tracker) * Claims linkage available, enabling heart-failure ground-truth ascertainment * Age \>= 45 years * At least one 13-week quarter in which at least one of the three quarterly features (mean BMI, standard deviation of body-water percent, 90th-percentile daily steps) can be computed Exclusion Criteria: * Users for whom heart-failure status cannot be determined from claims (unknown label; e.g. controls with \< 2 years of continuous enrollment) * Users with no usable measurement after per-reading plausibility screening * Users without an individual Withings account (shared accounts excluded to prevent data contamination)