Certain epidemics appear in life — illnesses that affect whole masses of the population and are therefore essentially a social concern. Ordinary materialistic science studies these illnesses by examining the physical organism of man. It knows nothing of the tremendous effect which the abnormal attitude of human beings to waking and sleeping life has upon epidemics and the susceptibility to epidemic diseases. Certain things take place in the organism during sleep and if they run to excess, they strongly predispose the human being to so-called epidemic diseases. Men and women who set organic processes in action as the result of too much sleep — I mean processes that ought not to take place, because waking life must not be broken up by such lengthy periods of sleep — these people have a much stronger predisposition to epidemic diseases and are less able to resist them.
Source: Rudolf Steiner – GA 314 – Hygiene – a Social Problem – Dornach, 7th April, 1920