Objective. Maternal smoking has been shown to be a risk factor for sudden infant death syndrome (SIDS). The effect of smoking by the father and other household members has not previously been examined.
Methods. A large nationwide case-control study. Four hundred eighty-five SIDS deaths in the postneonatal age group were compared with 1800 control infants.
Results. Infants of mothers who smoked during pregnancy had a 4.09 (95% confidence interval [CI] = 3.28, 5.11) greater risk of death than infants of mothers who did not smoke. Infants of mothers who smoked postnatally also had an increased risk of SIDS compared with infants of nonsmokers and, furthermore, the risk increased with increasing levels of maternal smoking. Smoking by the father and other household members increased the risk (odds ratio [OR] = 2.41, 95% CI = 1.92, 3.02 and OR = 1.54, 95% CI = 1.20, 1.99, respectively). Smoking by the father increased the risk of SIDS if the mother smoked, but had no effect if she did not smoke. In analyses controlled for a wide range of potential confounders, smoking by the mother and father was still significantly associated with an increased risk of SIDS.
Conclusion. Passive tobacco smoking is causally related to SIDS.