It is a very widely known, age-old problem, we are assured. 

My 8.6 pound Webster's Encyclopedic Unabridged Dictionary of the English Language from 1992, has quite a bit to say about sudden death, but it does not have anything to say about SADS. 

Perhaps it is not the age-old problem we are being told it is. 

Immediately after the keyword sudden, you will find a telling entry. 

Sudden death is described by my print dictionary as a sports term: "an overtime period in which a tied contest is won and play is stopped immediately after one of the contestants scores…"

Surely the phrase "sudden death" can mean that a human has suddenly died, however, the phrase "sudden death" is so foreign when referring to the adult human body, that such a definition goes unmentioned. 

Immediately after the keyword "sudden death," you will find another telling entry: sudden infant death syndrome. 

That term has long been a condition that occupies the minds of the public. Synonyms crib death or cot death are also mentioned in that entry. No mention is made of SADS, though this entry would be another natural place for editors to list this age-old problem. 

 When the memory-hole-prone interwebs and the deceptively inventive media tell you that a condition has always existed, sometimes it is good to turn to a print edition that someone was unable to change in the middle of the night.