I have an old colleage and a friend who developed severe memory loss in is 50’s due to his diving hobby (he did it without equipment). Shame since physically he was in better shape than most healthy 20 year olds. Breathing your own CO2 Or allowing the Oxygen content in your blood to decrease fir long periods is not healthy and the associated heart and brain function issues that might develop in the long term aren’t well know. This is again a case where the young and healthy are being sacrificed for the old and sick just so politician can assert control. Typically in movies it’s the other way around.