Researchers studied the brains of 27 infants. Nineteen died from SIDS, and eight died from other conditions. The team compared the level of various cytokines (a class of proteins involved in regulating the immune system) in the brains of each group. All 19 SIDS brains showed strong or moderate levels of interleukin-1 (a type of cytokine) in the same regions of the brain stem. Six of the non-SIDS brains had weak, negligible or no level of interleukin-1 in the same regions, and the other two had a moderate level.
"We detected a pattern of cytokine in the SIDS brain that could overturn a delicate balance in molecular interactions in vital brain centers," said study author Hazim Kadhim, MD, PhD, of Universit Catholique de Louvain and Free University in Brussels, Belgium. "It seems that high levels of interleukin-1 could be a common denominator in SIDS."
Cytokines like interleukin-1 could be released in the body in response to various stimuli, under infectious or inflammatory conditions, and when there is a lack of oxygen. Cytokines are not always harmful. When cytokines interact with neurotransmitters (substances that send nerve impulses across the brain), the result could change vital functions like arousal responses in the central nervous system, according to Kadhim. These modified arousal responses could cause SIDS.
The ages in each group were not exactly matched in the study. The infants with SIDS ranged six weeks to 10 months in age. The non-SIDS infants ranged one day to 18 months.
An editorial in the same issue of Neurology says the study results are subject to criticism because there is no agreement on what is a suitable control group to compare with SIDS
Contact: Marilee Reu
American Academy of Neurology