IIUC why medical cares at all, this is really insightful. Because as far as I'm aware, the medical industry basically uses birthdate as a key; it helps to (a) tell two patients with other primary keys (like name or address) apart and (b) do a quick mental-acuity check on the patient by just having them regurgitate the value and doing a human-brain string= on it.

The dose varies per age, but this isn't that exact.