Evidence has emerged that a chemical imbalance in the brain may play a key role in cot deaths.
Researchers found low levels of serotonin triggered changes in heart rate.
Serotonin is a neurotransmitter that passes messages between brain cells and is most associated with mood.
The research, by the European Molecular Biology Laboratory in Italy, follows similar findings in 2006 in the US.
About 300 babies die suddenly each year in the UK, although numbers have fallen by 75% since the early 1990s when a public campaign was launched to reduce the risks.
In the latest study, published in the journal Science, mice susceptible to sudden death had been engineered to slow the production of serotonin.
This affected the brain stem which is linked to the spinal cord and helps control the lungs and heart.