Cot death remains a mystery

A team from Brussels found the brains of children who had died from Sudden Infant Death Syndrome showed higher levels of interleukin-1.

They believe high levels of the chemical may make the nervous system less responsive to danger signs.

However, critics of the research, published in Neurology, say it failed to compare children of the same age.

The researchers studied the brains of 27 children, of which 19 died from Sudden Infant Death Syndrome (SIDS), and eight from other conditions.

All 19 SIDS brains showed strong or moderate levels of interleukin-1 in the same regions of the brain stem.

However, levels of the chemical were much lower in the children who had died from other conditions.

Cytokines like interleukin-1 are not always harmful, but they can interact with chemicals in the brain.

And the researchers believe it is possible that this interaction may change vital nervous system functions, including how quick it is to react to external stimuli.

Researcher Dr Hazim Kadhim, of Universit� Catholique de Louvain and Free University in Brussels, said: "We detected a pattern of cytokine in the SIDS brain that could overturn a delicate balance in molecular interactions in vital brain centres."

Flaws

However, critics of the study say the researchers say the failure to compare children of the same age makes it impossible to rule out the possibility that interleukin-1 levels fluctuate over time naturally.

The infants with SIDS ranged from six weeks to 10 months in age. The non-SIDS group ranged from one day to 18 months.

Dr Bradley Thach, of the Washington University School of Medicine in St Louis, said: "Since the SIDS and control infants were not age-matched, it's difficult to say how normal developmental changes in cytokine levels impacted the results.

"Another crucial question is what is the cause of elevated ctyokines in SIDS?"

A spokeswoman for the UK Foundation for the Study of Infant Deaths described the research as "interesting" but said it was too early to know whether it was significant.

"The first thing that needs to be done before we take it too seriously is for the work to be replicated, preferably in another lab, and the difficult question of appropriate controls also needs to be addressed."