SUDDEN-INFANT-DEATH-SYNDROME - INSULATION FROM BEDDING AND CLOTHING AND ITS EFFECT MODIFIERS

Background. Thermal stress related to excessive insulation from beddin g and clothing has been postulated to be associated with sudden infant death syndrome (SIDS). Methods. The parents of 393 (81%) of the infan ts who died of SIDS in the post neonatal period were interviewed at ho me. Interviews were also completed with the parents of 1592 (88.4% of total) controls, a representative sample of all hospital births. The s tudy was conducted in regions of both the North and South Island of Ne w Zealand in which 78% of all New Zealand births occurred in 1987-1990 . Temperatures for the infant's bedroom estimated from the outside tem perature and a model were used to predict the appropriate insulation f or the lower critical temperature (temperature below which the metabol ic rate is likely to increase). Results. Sudden infant death syndrome was associated with extra thermal insulation of > 2 tog above the lowe r critical value, the odds ratio (OR) was 1.70 (95% confidence interva l [CI] : 1.31-2.20) after adjusting for season, After adjusting for a number of confounding factors the OR was reduced to 1.35 (95% CI :0.97 -1.87). Also associated with SIDS was too little thermal insulation OR = 1.67 (95% CI : 1.13-2.48), and 2.63 (95% CI : 1.61-4.30) when adjus tments were made for the confounding factors. The interaction effect b etween infants sleeping prone and > 2 tog extra thermal insulation was significant (OR = 6.07, 95% CI: 3.83-9.60). Infants with too little t hermal insulation were at increased risk ii they were not tightly wrap ped (OR = 3.81, 95% CI : 2.04-7.09). There were also small additive in teraction effects if the mother smoked and the infants had > 2 tog ext ra thermal insulation, or if they were ill and had > 4 tog extra insul ation. Interaction effects between thermal insulation and other factor s were not significant. Conclusion. More thermal insulation than was n ecessary to maintain the lower critical temperature increased the risk of SIDS primarily among infants in the prone sleep position, and to a lesser degree in infants whose mothers smoked and in infants who were unwell.