Nicotine's double link to cot death
New research suggests why babies whose parents smoke tobacco are more likely to die of Sudden Infant Death Syndrome, or cot death.
The experiments show that nicotine produces a double whammy, not only directly disrupting a baby's breathing, but also disrupting the early development of the neural circuits that guard against the stopping of breathing during sleep.
Hugo Lagercrantz, one of the researchers at the Karolinska Institute in Stockholm, Sweden says: "I think it is most dangerous to smoke during pregnancy, because nicotine may set the sensors that detect low oxygen levels wrongly.
"If all pregnant women stopped smoking I think the incidence of SIDS could be reduced by at least 40 to 50 per cent in Sweden and the UK," he told New Scientist.
The key is a membrane protein in nerves, one of several that bind acetylcholine, an important transmitter of neural signals. One particular form of the receptor is also strongly activated by nicotine. The Swedish scientists, with colleagues in France, studied the breathing of sleeping mice with and without this form of the receptor.
Sleeping people stop breathing several times during the night, an event called sleep apnoea. Normally the resulting fall in blood oxygen partially wakes you, and breathing resumes. In SIDS babies, this response fails. It also failed in the mutant mice, meaning the receptor is needed to help detect low blood oxygen and re-start breathing after sleep apnoea.
Prolonged exposure to nicotine is known to desensitise the receptor, so exposure before birth might make the system less sensitive, and less likely to rouse a baby after sleep apnoea.
Another response to low oxygen is deeper breathing. But observation of the mice shows that nicotine dampens this directly, further reducing the ability to recover from sleep apnoea.
Knowing the specific acetylcholine receptor involved might allow the development of treatments to try to prevent the disorder, the researchers suggest. But the central message is the same as that of all studies of pregnancy and tobacco: if you are having a baby, don't smoke.
Journal reference: Proceedings of the National Academy of Sciences (doi/10.1073/pnas.192463599)
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