An explanation of the 25% male excess mortality for all children under 5

BACKGROUND: To demonstrate that an epidemiologic probability model of a hypothesized X-linkage for Sudden Infant Death Syndrome (SIDS) that predicted its 50% male excess, also predicts the 25% male excess of all child mortality for ages under 5 years.

METHODS: Neglecting trauma, infants die naturally from either respiratory causes R (breathing stops first) or cardiac causes C (heart stops beating first). An hypothesized dominant X-linked allele with frequency p = 1/3, that is protective against acute anoxic encephalopathy, predicted the 50% male excess of R. Given the ~ 0% male excess for cardiac deaths C, and assuming equal death risk for females by R and C, their average predicts a 25% male excess for equal numbers of infant males and females at risk. Thus, 5 males would die for each 4 females dying from all causes, predicting a male fraction of 5/9 = 0.55556.

RESULTS: Vital statistics for gender of children under 5 years at risk of dying and their corresponding mortality are obtained from the U.S.A. and multiple European countries. For 17 data sets from 15 countries, we total over 1.2 Billion child-years at risk and over 2.6 million child deaths. The observed total under 5 year male fraction, correcting for the nominal 5% male livebirth excess, is 0.55633, virtually as predicted.

CONCLUSIONS: An X-linked dominant allele protective against respiratory failure, predicts accurately the 5/9 male fraction of all child mortality under 5 years. DNA study of SIDS can identify the candidate X-linked gene locus.