Extreme and conventional cardiorespiratory events and epidemiologic risk factors for SIDS

To test the hypotheses that there is a lack of correlation between extreme events and epidemiologic risk factors for sudden infant death syndrome (SIDS), and if conventional events are normal, their numbers should increase once a circadian decrease in breathing rate is established. In addition, the number of events should decrease with maternal smoking.

Three outcome variables were derived from the Collaborative Home Infant Monitoring Evaluation (CHIME) of 1082 infants: (1) at least 1 extreme event lasting > or = 30 seconds, (2) at least 1 conventional event lasting > or = 20 seconds, and (3) being part of the 50% of infants with the most events.

Multivariate logistic regression analyses found that extreme events were not statistically associated with any known SIDS risk factors and occurred less often during the early morning. Healthy term infants had significantly fewer of these events compared with preterm infants, subsequent siblings of infants with SIDS, and infants with an apparent life-threatening event, a finding that was not evident after 43 weeks (3 weeks postterm). Conventional events increased during the night, whereas maternal smoking was associated with a decrease in conventional events. Apneic episodes persisting for > or = 40 seconds occurred in 1.8% of the infants.

Extreme events are associated with immaturity and do not seem to be immediate precursors of or causally related to SIDS.