In 8,292 All of Us participants with Fitbit data and no prior cardiovascular disease, each one-standard-deviation rise in average daily steps (3,299) was associated with lower odds of a first CVD record in outpatient care (OR 0.786, 95% CI 0.744-0.830) and in acute care (OR 0.659, 0.586-0.742), compared with no recorded CVD. Acute-care versus outpatient recording also favored more steps (OR 0.839, 0.742-0.948). Models adjusted for age, sex, smoking, and drinking.
The novelty here is the endpoint: separating where a diagnosis first appears, a quiet clinic visit or an emergency admission, hints that higher activity may shield against the more severe, abrupt presentations. That fits the large accelerometer literature linking steps to fewer cardiovascular events and lower mortality. But the caveats are heavy. This is a preprint, not yet peer reviewed, so the numbers may shift. The cohort is selected: Fitbit owners who completed surveys, with former smokers excluded and 1,470 early-event participants removed. Adjustment omits diet, income, BMI, and baseline health, so reverse causation is plausible, since people with brewing heart trouble walk less. The authors' own sensitivity tests show the acute-versus-outpatient gap approaching or crossing the null when 455 missing-setting cases are reallocated, so that contrast is fragile. The mediation findings were exploratory and inconclusive. Practically, this reinforces the familiar message that more daily movement tracks with better cardiovascular outcomes, without establishing a target or proving causation. Incremental and confirmatory.