Are there tests predictive for prolonged apnoea and SIDS? A review of epidemiological and functional studies.

Sudden infant death syndrome (SIDS) remains the predominant cause of postneonatal mortality. Epidemiological studies have led to the definition of populations with an increased risk for SIDS: subsequent siblings of SIDS victims, infants with near miss for SID episodes, prematurely born infants with perinatal risk factors, and infants of drug dependent mothers. Furthermore, a variety of additional although rarely independent factors regarding both mothers and infants have been found to be associated with an increased risk for SIDS. Despite of this, the majority of infants still dying from SIDS do not belong to one or more of these risk groups and even within a group considered to be at increased risk it is impossible so far to identify individual infants at highest risk on the basis of an infant's history and clinical data. Therefore, different methods have been applied during the last several years in order to detect functional abnormalities of cardiorespiratory control during sleep with the aim of obtaining more specific and sensitive predictors of subsequent severe apnoea and SIDS. In an attempt to evaluate the predictive power of these various methods the present article reviews their results in relation to the follow up data of the infants under study. The results of the meanwhile innumerous studies were found to be at variance and often controversial. At the present time, none of these tests may be looked at as virtually improving our ability to predict the risk for prolonged apnoea and SIDS. One of the reasons for this may be the lack of standardisation of the particular methods with respect to both definition of study groups and conditions of testing infants. Since all of these tests have mainly been performed in infants of epidemiological risk groups, the definition of which is an indispensable prerequisite for the evaluation of both the indication and the results of such tests, an updated survey of the more recent epidemiological studies is given as an introduction.