Health age (biological age)

Wearable vendors' longevity metric: compare measured health (VO2max, resting HR, sleep, HRV, optionally lab values like A1C and LDL) against chronological age — "is your body younger or older than you are?" Whoop age came first; Apple's version headlines the new Health app longevity tab (apple-watch). The recurring transparency gap: the formula and variable weighting are undisclosed, so users can't tell what moves the number or whether adding lab data matters — rob-ter-horst asked Apple directly and uses his own Whoop age as an active fitness motivator, which is exactly why an unexplained score is a problem. A vendor-claims case for reference-device-validation-style scrutiny, applied to derived metrics instead of sensors.

Source: report