Nicotine study finds new cot-death link

Expectant mothers should avoid nicotine, even nicotine chewing gum, as it raises the risk of cot death, a new study shows, suggesting that it is not enough for pregnant women to give up smoking.

Scientists have long known that babies of smoking mothers have a much higher risk of cot death than infants of non-smokers, but a Swedish-French study is the first to point to nicotine rather than smoking as the culprit.

"It's the nicotine itself that is dangerous. It doesn't matter if you're using nicotine chewing gum - it's just as bad," said Hugo Lagercrantz, who is a professor and paediatrician at the Karolinska Institute and initiator of the study.

Many women smokers, and their doctors, had assumed that chewing nicotine gum as a substitute for cigarettes during pregnancy was safe, said Mr Lagercrantz.

In cot death - also known as Sudden Infant Death Syndrome - apparently healthy babies, usually two to four months old, die in their sleep when breathing suddenly stops.

Normally receptors in the brain send an alarm to the nervous system when oxygen levels get too low during sleep.

The message brings sleepers back to consciousness, prompting them to open their mouth or turn over.

Nicotine disturbs this ability to regulate breathing during sleep, the research team found.

The study found genetically modified mice that lacked the "wake-up" receptor did not awake although breathing had stopped.

This receptor is also the one that responds to nicotine, so the scientists concluded that in growing foetuses these vital receptors become numb if exposed to nicotine, disturbing the wake-up reflexes and increasing the risk of cot death.

"The researchers proved that the reflex response to the lack of oxygen is diminished in the invalidated [modified] mice, suggesting the involvement of the receptor in this response," the report said.

None of the mice actually died as all were woken before oxygen levels became lethally low, said Mr Lagercrantz, who carried out the study at the Institut Pasteur in Paris with colleague Jean-Pierre Changeux and Philippe Evrard from the Hopital Robert Debre, also in Paris.

The study was published last week in the American journal Proceedings of the National Academy of Sciences.

In Europe, cot death afflicts about one baby in 2000. The rate is twice that in North America.

No apparent cause for cot death has ever been firmly established, though many theories have been put forward.

Said Mr Lagercrantz: "If women gave up nicotine altogether, the problem with cot death could probably be virtually eliminated."

- REUTERS

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