It is believed that serotonin helps to coordinate breathing, blood pressure and temperature during sleep. When a baby sleeps face down or with his or her face covered by a blanket or pillow, they are more likely to re-inhale the carbon dioxide that they just exhaled, not fresh, oxygenated air. “A normal baby will wake up, turn his or her head and start breathing faster when carbon dioxide levels rise,” said Dr. Hannah Kinney, study author in a press release. However, in a child with abnormal serotonin levels, his body may not react at all, the researchers theorize. In fact, 65 percent of the children in the study who died of SIDS were found sleeping on their side or stomach.
These abnormalities begin to develop in the womb, said Kinney, and may be caused by smoking or alcohol use by the mother while she is pregnant. The findings also explain why SIDS tends to affect children under six months of age, a time when their body is still developing to function independently outside of the womb. So, in an older child various mechanisms may be able to monitor breathing during sleep, but a baby may rely on this section of the brain stem.
“We think that these control systems reach full maturity only towards the end of the first year of life,” said Kinney.
Kinney hopes that her work will lead to the development of screening tests to identify those babies at risk for SIDS. She also believes that a treatment to protect children with this abnormality is a possibility.
“We provide strong evidence that SIDS is a biological problem, and that the brainstem serotonin system isn a good place to focus continued research efforts,” said Kinney.