We have made recent progress in identifying the mechanism: basically, many babies don't respond to rising carbon dioxide levels in their lungs the way older peo

We have made recent progress in identifying the mechanism: basically, many babies don't respond to rising carbon dioxide levels in their lungs the way older people do. They don't start breathing faster, or flail around trying to get a breath. Instead, they stop breathing & then, unless someone notices, die. See, for example: https://www.frontiersin.org/articles/10.3389/fneur.2015.00220/full https://www.frontiersin.org/articles/10.3389/fneur.2015.0022... It's why a ceiling fan can help: it produces positive air pressure that makes the infant get more oxygen. It's also why sleeping in a bed with a parent who smokes is such a risk factor: in an infant, even a mild an allergic reaction to cigarette smoke can be fatal. It is still unexplained by any specific diagnosis, because it's actually pretty common for infants to have an over-developed dive reflex and not to respond to excess carbon monoxide. But we know why it happens now.