Respiratory control during upper airway infection - Mechanism for prolonged reflex apnoea and sudden infant death with special reference to infant sleep position

The mortality rate of sudden infant death syndrome (SIDS) has been dramatic ally reduced after the supine sleeping position was recommended by health a uthorities. Concomitant with the decline an overall mortality rate, a marke d attenuation of the seasonal distribution has been observed. So far, neith er a satisfactory explanation of the previously noted seasonal variation, n or a generally accepted explanation for the preventive effect of supine sle eping position has been presented. Conceivably either the effect of some ye t unidentified risk factor for sudden unexpected death in infancy was more prevalent during the dark and cold months of the year during the period whe n infants generally slept prone, or the effect of the risk factor(s) was mo re potent in the prone sleeping infant. Prolonged apnoea in infancy may lea d to hypoxia, bradycardia and circulatory collapse. Reflex apnoea can be el icited by stimulation of chemoreceptors in the upper airway. The cardio-res piratory response to receptor stimulation is reinforced during a respirator y tract infection. Based on our own and others' experimental data, it is su ggested that the reduction in sudden infant mortality rate and in particula r the attenuation of the seasonal variation is in part an effect of the red uced likelihood of laryngeal chemoreceptors being stimulated by stagnated a irway secretions during upper airway tract infection in the supine sleeping infant. (C) 1999 Federation of European Microbiological Societies. Publish ed by Elsevier Science B.V. All rights reserved.