New evidence is suggesting that a chemical imbalance in the brain may be the cause of some cot deaths.
Scientists in Italy say they have found that low levels of serotonin in the brains of laboratory mice triggered changes in heart rate and body temperature that could lead to sudden death.
Serotonin is a neurotransmitter which is responsible for passing messages between brain cells, low levels of the chemical are associated with depression in humans.
The researchers from the European Molecular Biology Laboratory in Monterotondo, simulated Sudden Infant Death Syndrome (SIDS) in mice and found that the rodents were affected by levels of this chemical in the brain stem, the part of the brain which coordinates fundamental body functions including heart, lungs and temperature regulation.
The mice susceptible to SIDS carried a genetic fault which induced their brains to think they had too much serotonin and production of the chemical was consequently dropped to dangerously low levels and when the mice were placed in a cold chamber they could not keep themselves warm.
Study leader Dr. Cornelius Gross says at first sight the mice appeared normal but they suffered sporadic and unpredictable drops in heart rate and body temperature.
As a result more than half of the mice eventually died during a restricted period of early life, which was when the researchers made the link with SIDS.
The researchers say the experiment with the SIDS mice might help explain how faulty serotonin signalling can be life-threatening but say it is unclear to what extent the findings can be applied to humans but they hope their new findings will help identify which babies are most at risk from cot death.
Figures show that between 1985 and 2005, deaths from SIDS in Australia declined by 83%, from 523 deaths in 1985 to 87 in 2005 and this marked decline is strongly linked to a public health campaign which promoted the importance of safe sleeping practices such as placing babies to sleep on their back.
Despite a major public safety campaign in the UK which has cut cot deaths by three quarters since 1991, around 300 babies still die suddenly each year.
The research is published in the journal Science.