Accidental suffocation was long thought to be the primary cause. Some parents or their child’s caretaker mistakenly believed that a child might choke on its own vomit if it were placed on its back to sleep. In fact, the real risk was having its face buried in the soft bottom of its crib, leaving it unable to breathe. Children could also crawl under the covers of a blanket unable to escape, fatally limiting their oxygen intake during sleep.
About half of all SIDS deaths are thought to happen this way. That may be why the 1990s SIDS campaign, called “Back to Sleep,” was able to reduce the mortality rate by about the same percentage. But it hasn’t solved the riddle of SIDS. In fact, in polls, a shockingly high number of parents, especially African-Americans and Native Americans, still say they believe that children are safer sleeping on their stomachs – largely due to folk wisdom or inherited child-rearing practices. If those parents are still engaged in risky infant sleep practices, why do such a small percentage of their children die from SIDS?
The obvious answer is that other factors are at play – it’s just not clear what they are. For example, SIDS deaths are more likely to occur in colder climates, possibly due to a mild cold or upper respiratory infection occurring in infants with weakened immune systems. Nervous system dysfunction – either in the brain stem or in more peripheral areas — may also be a factor, as well as an abnormally large brain size (not resulting from simple edema or cerebral abnormalities). Maternal diet, vitamins, and breastfeeding have also been investigated and some degree of correlation has been found in each case.
In the end though, these explanations still largely amount to just medical speculation. Despite a spate of scientific studies, doctors are really no closer to understanding why SIDS appears when it does, and therefore, what preventative measures, besides sleep position, can reduce mortality.