SIDS risk 'four times higher for infants with family history'

Siblings of infants who died of SIDS are four times more likely to die of SIDS themselves, compared with newborns with no family history, data from more than two million births suggest.

The Danish cohort study suggested the risk could not be explained by prone sleeping or other environmental risk factors alone, pointing to a genetic association.

“Our finding… implies that inheritance plays a role in SIDS, which has important clinical implications for the surviving family because it warrants both clinical screening of family members as well as targeted genetic analysis,” said the researchers from the Copenhagen University Hospital.

As part of the registry-based study, the authors followed up more than 2.6 million children, born consecutively between 1978 and 2016, up until the age of one.

The cohort included nearly 1500 infants who died of SIDS (median age three months) during the 39-year study period, plus about 2400 of their younger siblings.

A total of eight siblings of a SIDS index case died at an average age of 2.5 months.

After adjusting for sex, age and calendar year, the authors found that infants with a family history of SIDS had a 4.3-fold higher risk of SIDS than infants without such a family history.

“Whether this familial aggregation is a consequence of shared environmental risk factors, genetic factors or a combination remains unknown, but our findings emphasise the importance of including a detailed family history of SIDS to identify siblings at risk of SIDS, with the goal to prevent further SIDS within families,” they concluded.

“Any child who died of SIDS who has a sibling should be investigated with great care to exclude genetic and/or environmental factors.”

Significantly, the researchers suggested the introduction of safe-sleeping campaigns in the early 1990s had no impact on mortality.

While the subsequent reduction in prone sleeping was associated with a dramatic decrease in SIDS in the general population, the siblings’ risk remained the same, according to an additional analysis of births between 2002 and 2016.

“The vast majority of infants who sleep in prone position, are exposed to tobacco smoke and get overheated during sleep do not die in infancy, and numerous infants with none of these risk factors have died of SIDS, suggesting that the aetiology is more complex,” they wrote in JAMA Network Open.

“[This view] is supported by our finding of familial aggregation and other studies showing involvement of various genetic pathways.”

However, they stressed the importance of continued efforts to reduce environmental risk factors.

Routine infant ECG screening was unlikely to have an impact on SIDS rates, they added.

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More information: JAMA Network Open 2023; 25 Jan.