Sudden infant death: Researchers find a cause

A perfectly healthy baby falls asleep and never wakes up. A new study confirms the thesis that a defect in the brain’s internal wake-up mechanism plays an important role.

Sudden infant death: when nothing remains of the beloved newcomer but a cuddly toy and memories.

Karin Hofer / NZZ

The fear of sudden infant death accompanies new parents in the first few months after the birth of their child. A baby who just stops breathing in his sleep, unnoticed, is a nightmare. You don’t just mourn the immeasurable loss, you rack your brains about what you could have done wrong, say those affected. So far, no causes of sudden infant death syndrome – abbreviated Sids, for Sudden Infant Death Syndrome – are known. A new Australian study has now found one.

“I hope we can at least take the guilt out of the parents concerned,” said researcher Carmel Therese Harrington to Australian media. She herself lost her newborn son to Sids thirty years ago. Since then she has been looking for causes.

Decreased activity of an important regulatory molecule

Her team at Children’s Hospital in Westmead has now found that in newborns who later died from Sids, a certain protein molecule was less active shortly after birth than in newborns who survived or died of other diseases. The data from 26 Sids babies were compared with those of 30 who died of other causes and with those of almost 600 newborns who were born at the same time but survived.

The researchers analyzed dried blood. A drop of blood is routinely taken from the heel of newborns two to three days after birth in order to diagnose various fatal metabolic diseases.

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The protein that is less active in Sids babies has the somewhat awkward name of butyrylcholinesterase, or BChE for short. It is found in the body in several organs and also in the brain. There it is involved in the communication between nerve cells. And it is one of the regulators of the automatic wake-up mechanism.

How does the wake-up mechanism work?

People of all ages have this. The system notices when there is too little oxygen in the blood and then switches on the brain’s internal blue light and siren. As a result, sleep is abruptly ended, the person wakes up – and begins to breathe.

Experts have long suspected that babies who suddenly die in their sleep and for whom no organic cause of death could be found have a problem with their waking mechanism. The new finding from Australia sounds very plausible: reduced BChE activity could lead to a weak wake-up mechanism. However, paediatricians emphasize that further and, above all, larger studies must now confirm this reduced BChE activity as a cause of Sids.

Recommendations for minimizing risk

The reduced BChE activity can explain why the wake-up mechanism fails. But in order to die, there must be another problem that leads to a drop in oxygen levels in the newborn’s blood.

Some such external factors have already been recognized in recent years. Anything that prevents the baby from breathing freely and deeply is considered a risk factor. Parents are therefore advised to only let their baby sleep on their back on a solid surface for the first few months, to use a sleeping bag instead of a duvet, and not to leave stuffed animals or other objects in bed that the little one could bury their face in. Also, the bedroom should not be too warm. Other significant risk factors for Sids are smoking parents and especially smoke in the child’s bedroom.

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Since this advice has been given and heeded, the number of Sids cases has decreased significantly. In Switzerland, 5 to 10 newborns die from it every year, in Germany it is between 130 and 150. But even if there are only a few cases, it remains a drama for the parents concerned.

Harrington now wants to develop a test that identifies newborns with an increased risk of Sids. The reduced BChE activity could be determined in routine blood tests in newborns. But the bigger, still unsolved problem is deriving further, targeted preventive measures from this knowledge.