What protects infants against SIDS?

The sudden, unexpected and medically unexplained death of a baby during sleep, sudden infant death syndrome (SIDS), is not yet fully understood. A European research group has now presented a new explanatory model in an article published in the current issue of the scientific journal Human nature.

This model focuses primarily on the exciting question of what role infants’ innate and acquired protective factors can play. “The resilience of babies to cot death is a so far unanswered question. We present an explanatory model for this,” says lead author and pediatrician Herbert Renz-Polster, affiliated with the Health Services Research of the Department of General Paediatrics, Pediatric Cardiology and Neonatology. at the University Hospital Düsseldorf.

Until now, cot death has mainly been explained by the influence of risk factors to which infants are exposed. For example, lying on the stomach to sleep, cigarette smoking by parents, too heavy bedding or an unfavorable sleeping surface. In fact, such risk factors play an important role in the development of SIDS, as the team of authors of the new study makes clear.

“Of course the risks count. SIDS cases without at least one of the known risk factors are extremely rare. In most cases, these tragic events carry multiple risks at the same time. Yet this is not enough for a comprehensive explanation,” says Prof. Dr. Freia De Bock, head of the Department of Health Research in Childhood and Adolescence, Department of General Paediatrics, Neonatology and Pediatric Cardiology and Center for Health and Society (chs) of the University Hospital Düsseldorf.

For example, it is unclear why the risk of cot death only increases so significantly after the neonatal period: why would a three-month-old baby be more sensitive to the typical risks of cot death than a three-week-old baby, the researchers wonder. their article. The same goes for the fact that male babies are apparently more susceptible to SIDS. The protective effect of breastfeeding against cot death has also not yet been definitively explained.

In the current publication, the scientists point out the limitations of the risk-based explanatory model. An analysis of the cot death data shows that this in itself is extremely poor at predicting cot death.

“More than 99 percent of babies with certain risks do NOT die from SIDS,” says Dr. Renz Polster. To answer this question, the multidisciplinary group analyzed previous studies on SIDS, based on interdisciplinary research in the fields of SIDS epidemiology, sleep research, anthropology, developmental pediatrics and pediatric public health, with a particular focus on the results of experimental pediatric research. .

According to these findings, infants develop a rich protective repertoire as part of their normal and healthy development, allowing them to respond competently and efficiently to adverse influences. The children who died of cot death were apparently unable to properly build up their protective repertoire. This is supported by the fact that it can be shown that the vast majority of SIDS victims have developmental delays, for example due to maternal smoking during pregnancy or severe preterm birth.

Looking at the protective factors could be particularly fruitful in explaining the ‘relative grace period’ at the beginning of life. “Research on early infants showed 100 years ago that infants in the first weeks of life are equipped with powerful protection: their innate neonatal reflexes. For example, these ensure that they can breathe freely. However, this ‘included’ protective shield must then be gradually phased out. replaced by an acquired and downright ‘trained’ protection program,” says Professor De Bock.

Previous SIDS researchers had already pointed out that this transition takes place between the second and fourth months of life – precisely in the developmental phase when SIDS is most common.

Babies with developmental problems seem to have a particularly difficult time with this transition phase. However, the child’s daily experiences also seem to play an important role. The team of authors refers to the theory of evolution, according to which the care experiences typical of the species were always also learning and training opportunities for the child to practice protective behavior.

Drinking at the mother’s breast is detailed in the article as an example of this, and observations from the 1960s even showed that this is also likely to involve practicing and expanding skills to ensure free breathing.

Based on these findings and considerations, scientists have now developed a comprehensive model for the development of SIDS, which they call the ‘evolutionary-developmental model’. According to this model, vulnerability to SIDS is based on an imbalance between risk factors and protective factors that form during the child’s development.

“For us, SIDS represents a fatal imbalance between current physiological challenges and the protective capacities we have acquired over development,” says Dr. Renz Polster.