A scientific review of the association between prone sleeping position and sudden infant death syndrome

A meeting was held in Canberra on 29 and 30 July 1991 to discuss the relationship between prone sleeping position and sudden infant death syndrome (SIDS). It was sponsored by the Australian Rotary Health Research Fund in association with the Sir Robert Menzies Memorial Foundation. The catalyst for the meeting was the recent paper in the Lancet reporting the results of the prospective study carried out by the Menzies Centre for Population Health Research in Hobart which reported an increased risk of SIDS for infants sleeping prone.     

Prematurity and sudden infant death syndrome. Polysomnography in question]

Systematic recording of cardiorespirographic events has been recommended by some authors in premature and/or very low birth weight infants before or shortly after hospital's discharge. Their objective is the recognition of babies at risk of sudden infant death syndrome (SIDS) and prevention by home monitoring. After an extensive review of the recent literature, prematurity itself does not appear as a risk factor of SIDS. Late apneas are common, but their prognostic significance remains uncertain. Although it is clear that bronchopulmonary dysplasia carries a greater risk of acute life threatening events and infantile death, their prevention mainly relies upon an adequate oxygen supplementation. As a consequence no more than the general infant population, premature infants require neither polysomnographic recording nor home monitoring.     

Prone position and unexpected sudden infant death

The authors have discovered that in all the epidemiological surveys, 80 to 90% of SIDS happen when the infant is lying prone and at the age of 2 or 3 months when the infant is able to turn his head. Comparing the position of infants who died of SIDS with that generally pertaining to infants in the region, they found a good correlation between SIDS and the prone position. It seems that SIDS is a multifactorial syndrome in which asphyxia has been abandoned too readily in favour of other causes which have not been proven. They would like similar surveys to be carried out. Pending the results of these studies and taking into account the other disadvantages of the prone position, they recommend a return to laying the baby on his side in a traditional fashion.     

Sleeping position and sudden infant death syndrome (SIDS): effect of an intervention programme to avoid prone sleeping

The proportion of prone sleeping among sudden infant death syndrome (SIDS) victims and infants in general, and the rate of SIDS were prospectively studied in the county of Hordaland, Norway, three years before (1987–89) and three years after (1990–92) a campaign to discourage prone sleeping. Before the campaign, 64% of random reference infants were put prone versus 8% after (p < 0.0001). Concurrently, the rate of SIDS decreased from 3.5 to 1.6 per 1000 live births (63 infants before and 30 after the campaign, p = 0.0002). Prone sleeping was not considered a statistically significant risk factor for SIDS before (OR 2.0,95% CI 0.8–4.5), but was highly significant (OR 11.3,95% CI 3.6–36.5) after the campaign. Prone sleeping is an important risk factor for SIDS, but the association may be missed in epidemiological studies if prone is the predominant sleeping position. Behaviour with regard to sleeping position may be changed rapidly by means of a simple campaign.     

Sleeping position and sudden infant death syndrome in Norway 1967-91

OBJECTIVE--To investigate, in a population based national study, the association between sleeping position of infants and the occurrence of sudden infant death syndrome (SIDS). DESIGN--A retrospective survey and registry based ecological study. A questionnaire based surveillance of sleeping position was obtained in a random sample (n = 34,799) and surveillance of SIDS was based on all infants born in Norway 1967-91, surviving the perinatal period. Variables studied from the questionnaire were usual sleeping position (placed), breast feeding at 3 months, and maternal smoking in pregnancy, and from the Medical Birth Registry maternal age, birth order, and birth weight. RESULTS--Proportion of infants sleeping prone increased from 1970 (7.4%) to 1989 (49.1%) and dropped in 1990 (26.8%) and 1991 (28.3%). Occurrence of SIDS increased from 1970 (1.1/1000) to 1989 (2.0) before dropping in 1990 and 1991 (1.1). IMPLICATION AND RELEVANCE OF RESULTS--A cause effect relationship between prone sleeping and SIDS as suggested in previous studies is supported by the present; and so far only, national study of infants' sleeping position.     

Circadian variations in sudden infant death syndrome: associations with maternal smoking, sleeping position and infections. The Nordic Epidemiological SIDS Study

AIM: To study circadian variation in the sudden infant death syndrome (SIDS) and possible associations with risk factors for SIDS. METHODS: A questionnaire-based case-control study matched for place of birth, age and gender was conducted in Denmark, Norway and Sweden: The Nordic Epidemiological SIDS Study. The study comprised 244 SIDS victims and 869 control infants between September 1992 and August 1995. The main outcome was hour found dead. RESULTS: A significant circadian pattern was observed among the 242 SIDS victims with a known hour found dead, with a peak at 08.00-08.59 in the morning (n = 33). Of the SIDS victims, 12% were found dead at 00.00-05.59, 58% at 06.00-11.59, 21% at 12.00-17.59 and 9.0% at 18.00-23.59. When comparing night/morning SIDS and day/evening SIDS (found dead 00.00-11.59 and 12.00-23.59, respectively), the proportion of night/morning SIDS was high among infants of smoking mothers (81% vs 53%, p < 0.001), infants with a reported cold (82% vs 64%, p = 0.007) and infants sleeping side/supine (81% vs 60%, p < 0.001). No associations were observed between hour found dead and other sociodemographic risk factors for SIDS. Risk (odds ratio and 95% confidence interval) of night/morning SIDS and day/evening SIDS was 7.0 (4.5-10.9) and 1.5 (0.8-2.5), respectively, for maternal smoking, 2.2 (1.5-3.1) and 0.6 (0.3-1.3), respectively, if the infant had a reported cold, 3.7 (2.1-6.6) and 3.1 (1.1-8.4), respectively, if the infant was put to sleep in the side position (supine reference), and 11.0 (5.9-20.2) and 21.6 (7.6-60.8), respectively, if the infant was put to sleep in the prone position. CONCLUSION: The observed higher proportion of night/morning cases in SIDS if the mother smoked, if the infant was reported to have a cold and if the infant was sleeping side/supine may contribute to the understanding of some epidemiological characteristics of SIDS.