[Smoking and sudden infant death syndrome]

Assessment of the causation relationship between two phenomena requires the demonstration of an epidemiological association, a temporal and asymmetric sequence, and a biological gradient and identification of the biological mechanism(s). All epidemiological studies on sudden infant death syndrome (SIDS) and smoking have encountered major bias and difficult data interpretation but they all have estimated that maternal smoking caused a 2 to 3-fold increased risk of SIDS. Nicotine may interact with non-neuronal nicotinic receptors in the lung, peripheral nicotinic cholinergic and adrenergic chemoreceptors, and brainstem nuclei and has been largely studied. More accurate knowledge concerning the biochemistry and specific features of nicotinic receptors will be useful to explain the way nicotine alters breathing at rest and during hypoxia. Uncertainty about the casual relationship in no way means the fight against smoking is not warranted.