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A baby may stop breathing while sleeping for no apparent reason. A new study has now found a possible cause of sudden infant death: a congenital enzyme deficiency.
An Australian research team writes in a specialist magazine that it has a possible warning sign for sudden infant death syndrome (Sudden Infant Death Syndrome, SIDS). Independent experts do not want to overinterpret the results of the study. SRF science editor Irène Dietschi classifies the findings.
What did the Australian researchers discover? They have tracked down a possible risk marker for sudden infant death syndrome, which could be used to identify children at risk at an early stage. This marker is an endogenous enzyme called butyrylcholinesterase (BChE). It is one of many substances that help to regulate vital circulatory functions in the body, such as breathing or heartbeat. The levels of the enzyme butyrylcholinesterase were lower in babies who died suddenly than in healthy ones.
How did the researchers find out? Shortly after birth, all infants are routinely pricked in the heel, a few drops of blood are taken from them and they are examined for certain metabolic disorders that one wants to rule out. These so-called newborn screenings are done all over the world.
The Australian researchers have now come up with the idea of examining such blood samples. They collected 26 samples from babies who later died of cot death, plus about the same number of samples from children who died of other causes. They compared these almost 60 blood samples with those of over 500 healthy babies. It was found that the babies who died of Sudden Infant Death Syndrome had slightly less of the enzyme butyrylcholinesterase in their blood.
Are the findings from the study a medical breakthrough? Judging by the attention the study is getting internationally, one might think so. Many media report a “breakthrough” and claim that the mystery of sudden infant death has been solved. But from an objective point of view, these results have to be put into perspective, because there are still many question marks. First, the size of the study: 26 deceased children is a very small number; the fact that the enzyme levels in them were slightly lower than in the comparison group could also simply be a coincidence. Much larger studies are needed to confirm the result. Second, doctors who are not involved criticize that it is not known what the normal value of this enzyme is.
So the question is whether the values measured in deceased babies are really too low and whether this can actually lead to sudden infant death syndrome. Incidentally, so does the lead author of the study, chemist Carmel Harrington of Children’s Hospital in Sydney, Australia.
Can the new findings prevent deaths? No, it’s too early for that. The hope is that readings of this enzyme could be included in newborn screening to identify children at risk. If you want to start here, you would first have to investigate in animal experiments whether butyrylcholinesterase really plays a role in regulating respiration, and Which matter it plays. So, babies who are deficient in this enzyme might not wake up if they get short of breath during sleep. At least one interesting starting point has been found with the enzyme butyrylcholinesterase. However, research is still a long way from solving the mystery of sudden infant death.
Why is research in this area so difficult? One theory for sudden infant death is that breathing and heart activity are miscontrolled in the brain. These mechanisms are very complex in terms of brain physiology – that’s what makes it so difficult to be able to determine a specific cause for sudden infant death. Other risk factors also play a role, for example being very underweight at birth, certain hereditary causes or if the mother smoked during pregnancy. Sleeping on your stomach also contributes to the risk.
How many children are affected by sudden infant death syndrome in Switzerland? In the past, almost a fifth of infants died from sudden infant death syndrome. From the late 1980s and early 1990s, the numbers fell sharply when large campaigns clarified the risk factors. Today, less than ten babies die from sudden infant death syndrome in Switzerland every year.