Sleep apnoea in infancy.

Serial polygraphic sleep studies were carried out in 86 index infants (33 'symptomatic', 24 siblings of infants with the sudden infant death syndrome (SIDS), 29 'near-miss' for SIDS) and 11 healthy controls. Brief (greater than or equal to 3 less than 6 sec) or prolonged (greater than or equal to 6 sec) obstructive apnoea was observed only in index caes, and coincided with symptoms due to associated illnesses (usually respiratory). Their prevalence was comparable in 'symptomatic' and 'near-miss' groups--39% and 35% respectively. Prolonged (greater than or equal to 20 sec) central apnoea was seen only in pre-term 'near-miss' infants. Dips in transcutaneous oxygen tension greater than or equal to 15 mmHg occurred during sleep in 17% of 'symptomatic' infants and 19% of 'near-miss' cases, usually in association with obstructive or central apnoea. Diminution or disappearance of these abnormalities following clinical recovery from 'minor' illnesses suggested that they were the result of such illnesses.