Sudden Infant Death Syndrome and the time of death: factors associated with night-time and day-time deaths

Objective To investigate the diurnal occurrence of Sudden Infant Death Syndrome (SIDS) and interaction with established risk factors in the infant sleeping environment. Methods A 3 year population-based case-control study, in five English Health Regions. Parentally defined day-time or night-time deaths of 325 SIDS infants and reference sleep of 1300 age-matched controls. Results The majority of SIDS deaths (83%) occurred during night-time sleep, although this was often after midnight and at least four SIDS deaths occurred during every hour of the day. The length of time from last observed alive until the discovery of death ranged from < l to 14 h but was not significantly different from the corresponding sleep period amongst the controls. Amongst the day-time deaths, 38% of the infants were observed alive 30 min prior to discovery and 9% within 10 min. The risk of placing infants asleep on their side was more marked for day-time deaths (interaction: P = 0.0001) nearly half of whom were found prone, while the risk associated with paternal smoking [OR = 3.25 (95%CI: 1.88-5.62)] was more marked for night-time deaths (interaction: P = 0.02). The adverse effect of unsupervised sleep recognized for night-time practice [OR = 5.38 (95%CI: 2.67-10.85)] was also significant for day-time sleep [OR = 10.57 (95%CI: 1.47-75.96)]. Significantly more (P = 0.002) unobserved SIDS infants (24.8%) were found with bedclothes over the head compared with those SIDS infants where a parent was present in the room (11.3%). Conclusions SIDS can happen at any time of the day and relatively quickly. Parents need to be made aware that placing infants supine and keeping them under supervision is equally important for day-time sleeps.