RESULTS FROM THE 1ST YEAR OF THE NEW-ZEALAND COT DEATH STUDY

New Zealand's high mortality rate from the sudden infant death syndrome (SIDS) prompted the development of the New Zealand cot death study. This report of the preliminary analysis of the first year of the data gives the major identified risk factors. One hundred and sixty-two infants who died from SIDS were compared with 589 control infants, who were a representative sample of all hospital births in the study region. Obstetric records were examined and parental interviews were completed in 96% and 89% of subjects respectively. Data were available for all the variables in this study in 95% of those interviewed, thus 128 cases and 503 controls make up the subjects of this report. As expected we confirmed many risk factors for SIDS including: lower socioeconomic status, unmarried mother, young mother, younger school leaving age of mother, younger age of mother at first pregnancy, late attendance at antenatal clinic, nonattendant at antenatal classes, Maori, greater number of previous pregnancies, lower birth weight, shorter gestation, male infant, admission to neonatal intensive care unit. In addition, however, we identified three risk factors which are potentially amenable to modification. These were the prone sleeping position of baby (odds ratio = 3.53, 95% confidence interval 2.26, 5.54), maternal smoking (1-9 cigarettes/day OR = 1.87, 95% CI = 0.98, 3.54; 10-19/day OR = 2.64, 95% CI = 1.47, 4.74; 20 +/day OR = 5.06, 95% CI = 2.86, 8.95) and breast feeding (OR = 2.93, 95% CI = 1.84, 4.67). After controlling for all the above variables, the relative risks associated with prone sleeping position (OR = 5.74), not breast feeding (OR = 2.45) and maternal smoking (OR = 1.83) were still statistically significant. These variables appear independent of each other in their association with SIDS. Population attributable risk was calculated for these three variables. In total these three risk factors may account for 79% of deaths from SIDS. If all parents stop putting their infants down to sleep in the prone position, do not smoke and breast feed their infants the SIDS mortality rate may fall from 4.0/1000 live births to less than 1/1000.