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.     

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.     

Prematurity,sleeping position and sudden infant death syndrome

Preterm birth and prone sleeping position significantly increase the risk of sudden infant death syndrome (SIDS). The reduced incidence of SIDS with supine sleeping has been well publicised, yet some prematurely born infants are slept prone at the high-risk age for SIDS. This may reflect inadequate educational targeting of high-risk groups and/or concerns about possible adverse effects of supine sleeping. In addition, parents may receive mixed messages about sleeping positions, as they witness their prematurely born infants being nursed prone on neonatal units, often for many weeks. In the neonatal period, the prone position improves oxygenation, tidal volume and compliance of preterm infants with respiratory distress. The limited data available suggest prone positioning is also beneficial for convalescent, preterm infants. Thus, it is not clear when the advantages of prone sleeping cease. Studies are required to determine when supine sleeping for prematurely born infants can safely be recommended and hence an unambiguous message given to parents.     

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.     

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.     

Sibling grief in reaction to sudden infant death syndrome

Much of the literature that exists regarding psychologic outcomes of sudden infant death syndrome (SIDS) has focused on parental grief or family response; at least two studies suggest that a SIDS death also affected siblings. It is believed that children who experience the death of a sibling due to SIDS do grieve. Factors related to bereavement are the child's age at the time of the sibling's death, special circumstances of the SIDS death, and explanations and grieving response of the parents. However, no information currently exists that characterizes the course of the grief response of these children. Studies have indicated that about 1 year is a normal grieving period for adults. This study was conducted to evaluate the time frame of children's grief response to the death of a sibling from SIDS. A questionnaire was designed that incorporated child grieving behaviors from several sources; 151 questionnaires were distributed to families in which a SIDS death had occurred in the past 16 years in Iowa and Illinois. Information was obtained from 43 families for 50 children who were older than 2 years of age at the time of the sibling's death. With respect to the length of children's grief response, 54% were reported to have grieved longer than 1 year and only 40% were reported to have grieved less than 6 months. Thus, it appears that the length of the grieving response for these children is similar to that described for adults.     

Antibodies to endotoxin core in sudden infant death syndrome

To assess the possible role of endotoxaemia in the pathogenesis of sudden infant death syndrome (SIDS), antibodies to endotoxin core (EndoCAb), which have previously been shown to be depressed by systemic endotoxaemia, were measured. IgG and IgM EndoCAb and total serum IgG and IgM were measured in serum samples from 25 children who had died from SIDS and 164 control children under 1 year of age. Twelve (48%) of the 25 children who had died from SIDS had no detectable IgG EndoCAb compared with 28 (17%) of the 164 control children, and this difference was concentrated in children aged less than 3 months. There was no significant difference between the two groups in the percentage of children with no IgM EndoCAb, nor in the total IgG and IgM concentrations. For IgM EndoCAb, the younger children who had died from SIDS had higher concentrations than the controls. These results suggest that, in children who have died from SIDS, due to either unusually early or severe exposure to endotoxin, maternal IgG EndoCAb have been depleted and early IgM EndoCAb triggered.     

Defining the sudden infant death syndrome

Sudden infant death syndrome (SIDS) is a term that was first proposed in 1969 for a distinctive subgroup of unexpected infant deaths that occur during the postneonatal period with relatively consistent clinical, epidemiological, and pathological features. This term played an important role by focusing attention on a major category of postneonatal infant death, providing support to grieving families, and diminishing the guilt and blame characteristic of these deaths. Unfortunately, the application of this term has become increasingly controversial. Some have applied it too liberally, and others not at all. According to the definition proposed in 1969, despite slight changes suggested in 1989, SIDS remains a diagnosis of exclusion. Although this syndrome has several distinctive features, including age distribution and apparent occurrence during sleep, there has been reluctance to include these features in the definition. The problems created by the lack of an adequate definition are discussed. A 2-tiered approach is suggested, with a more general definition intended primarily for case management and death administration, and a more restrictive one intended primarily for research purposes, which distinguishes those deaths closely fitting the classic SIDS profile from those with one or more less typical features.     

Glomerulosclerosis in the sudden infant death syndrome

In the past two decades, two groups of investigators have alleged that infants who die of the sudden infant death syndrome (SIDS) have excess numbers of sclerotic glomeruli in their kidneys. This double blind, case-control study was undertaken to test that assertion. Using microscopic sections of the kidney from 153 autopsies (99 SIDS infants and 54 control infants) in the National Institute of Child Health and Human Development (NICHD) Cooperative Epidemiologic Study of Risk Factors for SIDS, we counted relative numbers of sclerotic glomeruli in four fields of renal cortical tissue in two sections from each infant. Our results indicate that there is no difference between the two groups in regard to the proportion of sclerotic glomeruli.     

Neuronal apoptosis in sudden infant death syndrome

Although evidence shows that victims of sudden infant death syndrome (SIDS) suffer repetitive episodes of hypoxemia, only subtle abnormalities have been found in their brains by light microscopy. The aim of the present study was to determine whether apoptosis, a form of cell death that can be triggered by hypoxemia and that leaves no scarring detectable by light microscopy, would be present in hypoxia-sensitive brain regions of SIDS victims. We looked for the presence of apoptosis with an in situ end-labeling method that detects DNA fragmentation. We studied 29 SIDS victims who were age-matched to nine control cases. We found significant neuronal apoptosis in 79% of the SIDS cases: 55% of the cases positive in the hippocampus and 96% positive in the brainstem. Whereas the distribution of apoptosis in the hippocampus was in hypoxia-sensitive subregions, the distribution in the brainstem was mostly in dorsal nuclei, including those involved with sensation in the face and position of the head (nucleus of the spinal trigeminal tract and vestibular nuclei). The control cases showed no significant apoptosis in the hippocampus and a mild degree in the brainstem in three cases. Our results indicate the occurrence of an acute insult at least several hours before death, an insult from which the infants had apparently recuperated. This suggests that SIDS victims suffered repeated apoptosis resulting in significant neuronal damage and, thus, functional loss in key brain regions. The involvement of specific nuclei in the brainstem may be linked to the fact that prone sleeping is a significant risk factor for SIDS. Enhanced neuronal death by apoptosis may thus have major implications for understanding the sequence of events leading to SIDS.