Are risk factors for sudden infant death syndrome different at night?

AIMS To determine whether the risk factors for SIDS occurring at night were different from those occurring during the day. METHODS Large, nationwide case-control study, with data for 369 cases and 1558 controls in New Zealand. RESULTS Two thirds of SIDS deaths occurred at night (between 10 pm and 7 30 am). The odds ratio (95% CI) for prone sleep position was 3.86 (2.67 to 5.59) for deaths occurring at night and 7.25 (4.52 to 11.63) for deaths occurring during the day; the difference was significant. The odds ratio for maternal smoking for deaths occurring at night was 2.28 (1.52 to 3.42) and that for the day 1.27 (0.79 to 2.03); that for the mother being single was 2.69 (1.29 to 3.99) for a night time death and 1.25 (0.76 to 2.04) for a daytime death. Both interactions were significant. The interactions between time of death and bed sharing, not sleeping in a cot or bassinet, Maori ethnicity, late timing of antenatal care, binge drinking, cannabis use, and illness in the baby were also significant, or almost so. All were more strongly associated with SIDS occurring at night. CONCLUSIONS Prone sleep position was more strongly associated with SIDS occurring during the day, whereas night time deaths were more strongly associated with maternal smoking and measures of social deprivation.