The siblings of infants who have died as a result of cot death have a four-fold increased risk of dying in the same way, a large study has found.

Cot death, or sudden infant death syndrome (SIDS), refers to the sudden, unexpected death of an infant while they are sleeping, which remains unexplained even after a thorough investigation.

According to the National Paediatric Mortality Register, the number of cases of SIDS in Ireland has fallen significantly in recent decades. However, it still remains the leading cause of death in infants between the ages of four weeks and one year.

The exact cause of SIDS is unknown, but it is thought to be caused by a combination of genetic and environmental factors.

The fall in cases of SIDS worldwide is thought to be due to various public health campaigns, which encourage people to place their babies on their backs when they are going to sleep, and to avoid smoking during pregnancy or around children.

"However, SIDS remains a leading cause of death during the first year of life, affecting thousands of infants each year in Europe and the US," commented the study's author, Dr Charlotte Glinge, of the University Hospital of Copenhagen in Denmark.

The aim of this latest study was to determine whether siblings of infants who have died as a result of SIDS, have a higher risk than the general population.

It looked at almost 2.5 million infants who were under the age of 12 months between 1978 and 2015.

The researchers found that the siblings of SIDS victims were four times more likely to also die from SIDS compared to children in the general population.

Dr Glinge insisted that a post-mortem examination by a cardiac pathologist should be undertaken in all cases of SIDS. She said that while SIDS is believed to be due to a combination of genetic and environmental factors, if a genetic mutation is identified that may have contributed, siblings and parents should be tested for that mutation.

She also said that all parents should be asked about family history of sudden cardiac death, and parents and siblings should be offered cardiology tests, including an electrocardiogram (ECG), in order to provide the best chance of identifying an inherited cardiac condition.

"All parents should follow public health advice on how to prevent SIDS. But by screening families of SIDS victims, we can identify whether there are additional steps that can be taken to stop a sibling dying of SIDS," Dr Glinge added.

Details of these findings were presented at EHRA 2018, a European Society of Cardiology congress, in Barcelona.

For more information on First Light, which supports suddenly bereaved parents and families in Ireland, click here