SIDS Symptoms May Be Misleading

The study, funded by the U.S. National Institute of Child Health and Human Development (NICHD), was published in the May 2, 2001, issue of The Journal of the American Medical Association (JAMA).

Breathing stoppage, or apnea, and slowed heart rate have long been observed in infants at increased risk for SIDS. Therefore, researchers have assumed that these events could be interrupted in order to prevent SIDS. The study used specially designed electronic monitors in the home to detect such cardiorespiratory episodes and revealed that this assumption might not be true.

Researchers followed 1,079 infants during their first six months after birth, classified as healthy or at increased risk of SIDS. They found that apnea and bradycardia occurred frequently, even in healthy babies who were born full-term. However, the most extreme events, those that lasted a very long time by usual medical standards, were common only in infants born prematurely and were found to be associated with significant decreases in blood oxygenation. Moreover, most occurred prior to the age when SIDS is most common (between two and six months of age).

These results cast serious doubt on the idea that extreme cardiorespiratory events are immediate precursors of SIDS, say the researchers. In addition, the extreme events were frequently associated with airway obstruction, which would probably not have been detected by the home monitors available for use by parents. The researchers stressed that the study did not address whether home monitoring decreases the incidence of SIDS or whether extreme cardiorespiratory events are markers of vulnerability to SIDS.

"The difference in when extreme events most commonly occur and when SIDS is most likely to occur suggests that these events are not immediate precursors to SIDS, as was once thought,” said Dr. George Lister, one of the authors of the study. "Recognizing that there will still be infants who some clinicians wish to have monitored at home, these study results have important implications for future design of monitoring devices.”