infant death vs sleep apnea

infant death and sleep apnea both are nouns.

Word	Noun	Adjective	Verb	Adverb
infant death	Yes	No	No	No
sleep apnea	Yes	No	No	No

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

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

Other hypernyms of infant death include death.

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