Sudden infant death syndrome and environmental temperature: further evidence for a time-lagged relationship.

All cases of sudden infant death syndrome that occurred in New South Wales in the period January 1, 1981 to November 30, 1985 were studied in relation to the environmental temperature which was recorded in Sydney. A significant (P = 0.009) negative correlation was found between a change in temperature and a change in the incidence of sudden infant death syndrome six days later. The size of the effect was such that a fall in temperature of 1 degree C was associated with an increase in the incidence of sudden infant death syndrome of about 6.5% (95% confidence interval, 1.7%-11.3%). This effect was over and above the usual seasonal variation in the incidence of sudden infant death syndrome.