... perhaps the main factor is the "crowded living conditions"...

then there should be also a study to look into past-war-army-soldiers (regular drafts, no war)...
(and even later, the vaccinated soldiers)

all in a smoothie, they would be healthier since lemon peel pulls out radiation, toxins, toxic heavy metals from the body without pulling out the good minerals. A woman past 70 I know has the strength and good looks of a much younger person since she has done that daily for many years.