Prone sleeping position increases the risk of SIDS in the day more than at night

SIDS mortality is higher during the night than in the day.

(1) To examine risk factors for SIDS by time of day and (2) to see if the proportion of deaths at night has changed from prior to the 'Back to Sleep' campaign, which recommended infants sleep supine.

A large population-based SIDS matched case-control (GeSID) study conducted from 1998 to 2001 (when the prevalence of infants placed prone to sleep was 4.1%). The reference sleep of the controls was matched for the estimated time of death for the case. Risk factors for SIDS were examined for night-time and day-time deaths. The estimated time of death was compared with that from an earlier study in Germany (1990-1994 when prevalence of prone sleeping was 32.2%).

There were 333 SIDS cases and 998 matched controls. The increased risk with placed prone to sleep was significantly different during the day [adjusted OR = 18.15 (95% CI = 5.91-55.69)] compared with during the night [adjusted OR = 3.49 (95% CI = 1.46-8.39; p-value for interaction = 0.011)]. There was no significant difference in the other risk factors examined by time of day in the multivariate analysis. The mean time found dead was 09:07. In the earlier study the mean time found dead was 08:54 and the difference was not significant (p = 0.57).

This study confirms previous observations that prone sleeping position carries a greater risk during the day than at night. However, the reduction in infants sleeping prone has not been associated with a reduced number of deaths in the day in Germany.