Cot death could be caused by a genetic defect which means babies who stop breathing cannot kick-start their lungs, research suggests.
Cot death largely remains a mystery
A University of Bristol team has discovered brain cells that generate nervous impulses essential for gasping, but not normal breathing.
They believe a deficiency in these cells could explain some cases of unexplained baby deaths.
Details appear in the journal Nature Neuroscience.
Cot death is the most common cause of death in babies under a year old, claiming 349 lives in the UK in 2004.
However, death rates have dropped by 75% since a public awareness campaign - which recommended parents put their baby to sleep on its back - was introduced in 1991.
Cot death has long been thought to be linked to a failure to gasp, but the reason why this should happen has not been known.
The Bristol team joined forces with US researchers to discover that many different types of brain cells are essential for normal breathing - but only a small subset of these - dubbed pacemakers - play a role in the gasping reflex.
If normal breathing should stop this backup system is activated to induce gasping. This restores oxygen supplies and kick starts the heart beat so that normal breathing can resume.
The researchers found that pacemaker cells were dependent upon a protein that forms a tiny hole or pore within the membrane of the cells.
When oxygen levels are low this pore opens more to allow the passage of sodium ions into the cell and provides a way in which gasping can occur automatically.
The team showed that when this pore was blocked it eliminated pace making and the ability to gasp.
Consequently, the heart would fail and death would be inevitable.
This raises the possibility that a genetic defect in this special protein found in pace making cells could prevent gasping.
Researcher Professor Walter St John said: "Our findings are exciting they demonstrate that emergency breathing, or gasping, is regulated by different mechanisms than those for normal breathing."
Joyce Epstein, director of the Foundation for the Study of Infant Deaths, said cot deaths were likely to be caused by a variety of factors.
She said: "Though we now know many ways of reducing the risk of cot death, we still don't know the causes of these tragedies.
"We need much more research, so that we can advise parents and health professionals as to what other preventative steps they can take to protect babies from the risk of cot death."