SIDS vs sleep apnea

SIDS and sleep apnea both are nouns.

Word	Noun	Adjective	Verb	Adverb
SIDS	Yes	No	No	No
sleep apnea	Yes	No	No	No

As nouns, sleep apnea is a hypernym of SIDS; that is, sleep apnea is a word with a broader meaning than SIDS:

SIDS: sudden and unexpected death of an apparently healthy infant during sleep
sleep apnea: apnea that occurs during sleep

Other hypernyms of SIDS include death.

SIDS (noun)	sleep apnea (noun)
sudden and unexpected death of an apparently healthy infant during sleep	apnea that occurs during sleep