Inverse relationship between risk of SIDS and early neonatal mortality: study of state mortality rates

It was predicted that at the state level early neonatal (0-6 days) mortality rates and rates for sudden infant death syndrome (SIDS) in the age range 7-364 days would be negatively correlated. Using published data for each of the 50 states and the District of Columbia over the 5-year period 1980-1984, the actual correlation was -0.68 (p less than 0.001). In a breakdown of early neonatal mortality by age at death, rates for infants aged less than 1 hour proved to be the exception; their rates were not found to be negatively correlated with the rates for SIDS (r = +0.20). This finding probably reflects uniformity in the quality of obstetric care. The geographic variation in mortality rates for infants aged 1 hour to 6 days might be explained by variation in the probability of a mother and fetus sharing one or more HLA antigens.