An 8 year study of risk factors for SIDS: bed-sharing versus non-bed-sharing.

BACKGROUND: It is unclear if it is safe for babies to bed share with adults. In Ireland 49% of sudden infant death syndrome (SIDS) cases occur when the infant is bed-sharing with an adult. OBJECTIVE: To evaluate the effect of bed-sharing during the last sleep period on risk factors for SIDS in Irish infants. DESIGN: An 8 year (1994-2001) population based case control study of 287 SIDS cases and 831 controls matched for date, place of birth, and sleep period. Odds ratios and 95% confidence intervals were calculated by conditional logistic regression. RESULTS: The risk associated with bed-sharing was three times greater for infants with low birth weight for gestation (UOR 16.28 v 4.90) and increased fourfold if the combined tog value of clothing and bedding was > or =10 (UOR 9.68 v 2.34). The unadjusted odds ratio for bed-sharing was 13.87 (95% CI 9.58 to 20.09) for infants whose mothers smoked and 2.09 (95% CI 0.98 to 4.39) for non-smokers. Age of death for bed-sharing and sofa-sharing infants (12.8 and 8.3 weeks, respectively) was less than for infants not sharing a sleep surface (21.0 weeks, p<0.001) and fewer bed-sharing cases were found prone (5% v 32%; p = 0.001). CONCLUSION: Risk factors for SIDS vary according to the infant's sleeping environment. The increased risk associated with maternal smoking, high tog value of clothing and bedding, and low z scores of weight for gestation at birth is augmented further by bed-sharing. These factors should be taken into account when considering sleeping arrangements for young infants.     

SIDS risk factors and factors associated with prone sleeping in Sweden

Objective

To compare the current prevalence of risk factors for sudden infant death syndrome (SIDS) in Sweden with a decade earlier, and assess factors associated with prone sleeping.

Methods

The results of a cohort study (Infants of Western Sweden) and a population based case‐control study (Nordic Epidemiological SIDS Study) were examined. Subjects were 5600 healthy 6 month old infants born in 2003 in the Western Sweden region and 430 healthy Swedish infants born between 1991 and 1995.

Results

Prone sleeping decreased from 31.8% to 5.6% and supine sleeping increased from 35.3% to 47.3%. Side or side/supine sleeping increased from 25.2% to 43.8%. Maternal smoking during pregnancy decreased from 23.5% to 9.5%. The risk for prone sleeping increased if the mother was unemployed (OR 2.4, 95% CI 1.5 to 4.0), if she was a heavy smoker in the third trimester (OR 44.1, 95% CI 1.6 to 1199.6), and if the child was irritable (OR 2.5, 95% CI 1.3 to 5.1), shared a bedroom with siblings (OR 2.6, 95% CI 1.0 to 6.6), or never used a dummy (OR 3.2, 95% CI 1.9 to 5.4).

Conclusions

Parents have complied with advice to prevent SIDS given at infant welfare centres for the last 10 years. A change in the preferred sleeping position from side variants to exclusively supine, and reducing the number of pregnant women smoking may be beneficial. Use of a prone sleeping position was associated with maternal employment status, maternal smoking, temperament of the child, dummy use, and sharing a bedroom with siblings.     

Interactions between maternal smoking and other prenatal risk factors for sudden infant death syndrome (SIDS)

Abstract In numerous investigations, maternal smoking increases the risk of sudden infant death syndrome (SIDS). In the present study we investigated whether prenatal risk factors for SIDS modify the effect of maternal smoking on SIDS mortality. We analysed data from a population-based cohort study (222 cases, 260,604 infants at risk) within the Westphalian Perinatal Inquiry in Germany between 1990 and 1994. In the stratified analysis, smoking was classified into non-smoking, moderate (1–10 cigarettes/d) and heavy smoking (> 10 cigarettes/d). Multiplicative interactions between smoking and other prenatal risk factors were assessed in a logistic regression model. The relative risk (RR) for maternal smoking was 2.4 (95% confidence interval 1.7-5.4) for moderate and 7.2 (5.3, 9.7) for heavy smokers. Previous established risk factors for SIDS, such as preterm birth, low birthweight, and number of prenatal visits did not increase the risk of SIDS among non-smokers, but became important risk factors among smokers. In preterm infants (< 37 weeks) of heavy smokers, the RR was 19.6 (10.4, 36.8) compared to term infants of non-smokers. Low birthweight infants (< 2500 g) of heavy smokers had a RR of 16.3 (8.4, 31.2) compared to normal weighted infants of non-smokers. Adjustment for occupational status did not change the crude estimates. The RR of < 6 prenatal visits in the heavy smoking subgroup was 14.8 (7.2, 29.6) compared to > 9 prenatal visits in the nonsmoking strata. Heavy smoking potentiates other prenatal risk factors for SIDS suggesting an increased susceptibility towards the adverse effects of tobacco smoke in utero. In infants born to non-smoking mothers, prenatal risk factors are absent and postnatal factors may be of major importance.     

What else do SIDS risk prediction scores predict?

Various aspects of the medical and social history of 12 743 children examined at the age of 5 years were related to two risk scores for the sudden infant death syndrome (SIDS) computed from data collected in the neonatal period. Children at high risk of SIDS were also at high risk of pneumonia, non-accidental injury and repeated or prolonged hospital admissions. There were stronger associations, however, with factors indicating social disruption and environmental disadvantage.     

Nicotine and cotinine levels in pericardial fluid in victims of SIDS

Milerad J, Rajs J, Gidlund E. Nicotine and cotinine levels in pericardial fluid in victims of SIDS. Acta Paediatr 1994;83:59–62. Stockholm. ISSN 0803–5253
We have analyzed the levels of nicotine and cotinine in pericardial fluid in 24 consecutively autopsied cases of sudden unexpected death in infants aged one to six months. Our aim was to determine to what extent victims of sudden infant death may have been exposed to passive smoking near the time of death. Sixteen of the decreased infants were classified as SIDS at autopsy. Other contributing causes of death, predominantly infections, were found in eight cases. Eight infants (30%) had cotinine levels less than 2 ng, indicating that no significant exposure to nicotine had occurred near the time of death. Of the remaining 70%, five had been moderately exposed, seven markedly exposed and four heavily exposed (cotinine levels 2–10 ng, 10–50 ng and more than 50 ng, respectively). Since only 18% of Swedish women smoke after childbearing we conclude that nicotine exposure in infants who died suddenly was much higher than one would otherwise expect. It is hypothesized that high concentrations of nicotine and nicotine metabolites around the heart may affect cardiac function and thus play a role in the mechanisms causing SIDS or other categories of sudden unexpected death.     

Sudden infant death syndrome: risk factors for infants found face down differ from other SIDS cases

OBJECTIVE: To test the hypothesis that infants with sudden infant death syndrome (SIDS) found face down (FD) would have SIDS risk factors different from those found in other positions (non-face-down position, NFD). STUDY DESIGN: We used the New Zealand Cot Death Study data, a 3-year, nationwide (1987 to 1990), case-control study. Odds ratios (univariate and multivariate) for FD (n = 154) and NFD SIDS (n = 239) were estimated separately, and statistical differences between the two groups were assessed. RESULTS: Of 12 risk factors for SIDS, there were 8 with a statistically significant difference between FD and NFD infants. After adjustment for the potential confounders, younger infant age, Maori ethnicity, low birth weight, prone sleep position, use of a sheepskin, and pillow use were all associated with a greater risk of SIDS in the FD than the NFD group. Sleeping during the nighttime, maternal smoking, and bed-sharing were associated with a risk of SIDS only in the NFD group. Pacifier use was associated with a decreased risk for SIDS only in the NFD group, whereas being found with the head covered was associated with a decreased risk for SIDS for the FD group. CONCLUSIONS: Infants with SIDS in the FD position appear to be a distinct subgroup of SIDS. These differences in risk factors provide clues to mechanisms of death in both SIDS subtypes.     

Changes in parental risk behaviour after an information campaign against sudden infant death syndrome (SIDS) in Norway

AIM: To assess parental risk behaviour before and after a sudden infant death syndrome (SIDS) information campaign with special emphasis on associations with maternal age, education, marital status and birth order. METHODS: Data from questionnaires sent to all mothers who gave birth in Norway during a period before the campaign were compared with corresponding data obtained after the campaign. RESULTS: Prevalence of non-supine sleeping position decreased from 33.7% to 13.6% while changes in smoking, non-breastfeeding and co-sleeping were disappointing. Risk factors were particularly prevalent in young mothers, but also in mothers with a minimum period of education, non-cohabitation and at birth order 2+. CONCLUSIONS: Non-supine sleeping decreased to a level that has never been reported before. In future campaigns, subgroup-specific measures may be needed.     

Mothers' knowledge of the risk factors and anxiety about SIDS

Objective : To assess the impact on mothers' knowledge and anxiety of the 1991-92 health promotion campaign on Sudden Infant Death Syndrome (SIDS) risk factors.
Methodology : A telephone survey of a population based sample of 339 mothers in Victoria, Australia, conducted 1992-94.
Results : Recall by mothers of the risk factors for SIDS was as follows: not breast-feeding. 15%; smoking, 46%; overheating, 48%; and prone sleeping, 84%. Recall rate increased as the campaign progressed. Receiving the campaign pamphlet was associated with an increased recall of all risk factors. Discussion of the pamphlet with a health professional was rare (9%). One-third of all mothers reported being very worried about cot death when caring for their babies. Self-reported worry was significantly more common among mothers whose babies were born at the time of the campaign introduction.
Conclusions : The campaign pamphlets were effective in increasing knowledge of the risk factors. The limited discussion with health professionals suggests that future campaigns need increased professional involvement to address problems, including anxiety among new mothers.     

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.     

Sudden infant death syndrome risk questionnaire: a mirror of parental awareness rather than a prospective diagnostic tool

AIM: In 1989, a scoring system that aimed to identify infants at risk of sudden infant death syndrome (SIDS) by a structured questionnaire [SIDS risk questionnaire (SRQ)] consisting of 25 items was introduced in Styria (Austria). It was the aim of the study to compare SIDS rates in the population that had access to the SRQ with the population that had no access. Furthermore, for the population receiving the SRQ, the responding (compliant) and non-responding (non-compliant) groups were compared concerning the incidence of SIDS. METHODS: Within the study period, 53 865 births and 57 SIDS cases were recorded (incidence 1.06/1000) and analysed retrospectively. RESULTS: The incidence of SIDS was significantly higher in the non-responding population (2.36/ 1000) than in the responding group (0.81/1000, p < 0.001). However, the incidence of SIDS was not significantly different in the population that had access to the risk questionnaire (1.29/1000) and the group without access (0.86/1000, p = 0.145). CONCLUSION: The value of any questionnaire used for SIDS prevention may be limited by the existence of a non-compliant population which represents a risk group and should be targeted by other preventive measures.     

Sudden infant death syndrome (SIDS) in South Australia 1968-97. Part 2: the epidemiology of non-prone and non-covered SIDS infants

OBJECTIVE: To identify the risk factors for infants who die suddenly and unexpectedly, but whose deaths are not related to prone position, or having the head covered. METHODOLOGY: A case-control study was designed in which the cases were infants who had died of sudden infant death syndrome (SIDS) in South Australia between January 1974 and December 1997, who were found not prone, not bed sharing and with the head not covered. The controls were two infants for each case, born in the same year and found in the prone position (again not bed sharing and with the head not covered). RESULTS: Sudden unexpected death infancy is rare in non-prone infants with the head not covered. occurring on average twice a year in South Australia, where there are 18,000-21,000 births per year. In this group there was a higher percentage of infants with features associated with low socio-economic groups (teenage pregnancies and maternal smoking), sibling SIDS, suspicion of non-accidental injury and the presence of minor congenital anomalies, especially cardiac anomalies. CONCLUSIONS: The majority of unexpected deaths in infancy can be prevented by not allowing infants to be unobserved in prone position, and by preventing them from getting their faces covered. For the few infants not found in these positions, a careful investigation should be made for malformations or non-accidental injury.     

Postnatal depression and SIDS: A prospective study

Abstract This study was carried out in response to reports from nurses to a post-neonatal mortality review committee that a number of mothers of infants dying from sudden infant death syndrome (SIDS) appeared to be depressed before the child's death. The New Zealand Cot Death Study was a 3 year multicentre case-control study for SIDS. There were 485 SIDS cases in the post-neonatal age group in the study regions, and these were compared with 1800 control infants. Infants of mothers with either a self-reported use of medication for psychiatric disorders, a history of hospitalization for psychiatric illness or a family history of postnatal depression had a significantly increased risk of SIDS compared with infants of mothers who were either not using medication (odds ratio (OR) = 1.45; 95% confidence interval (Cl) = 1.03, 2.04) or were without a history of hospitalization for psychiatric illness (OR = 1.80; 95% Cl = 1.03, 3.11) or a family history of postnatal depression (OR = 1.61; 95% Cl = 1.06, 2.43). All mothers of infants born in the study areas over a 1 year period were eligible to complete a questionnaire measuring maternal depression when the infant was 4 weeks of age. Thirty-three infants subsequently died from SIDS, and they were compared with 174 controls. Fifteen (45.5%) of the mothers of cases were depressed, compared with 28 (16.1%) of the mothers of controls. This prospective study found that the infants of those mothers that were depressed were more likely to die from SIDS than those of the non-depressed mothers (OR = 4.35; 95% Cl = 1.82, 10.37) and postnatal depression as a risk factor for SIDS was still significant after controlling for possible confounding variables (OR = 3.37; 95% Cl = 1.24, 9.12). We conclude that postnatal depression is a risk factor for SIDS.     

Prevention of deformational plagiocephaly in neonates

Background

Since the early 90s a striking rise in deformational plagiocephaly (DP) has been reported, and a causal link between the “back to sleep” position recommended to reduce the risk of sudden infant death syndrome. Recent data suggested that supine position is a risk factor only when combined with other environmental factors

Objective

To evaluate the impact of early intervention in the newborn environment on the prevalence of DP at 4 months of life.

Methods

A multicentric, prospective, controlled study in healthy term neonates. Within 72 h of birth, all parents received the usual recommendations for positioning their infants to prevent sudden infant death syndrome. In the Intervention group, recommendations were also given to encourage spontaneous and unhindered physical movement. At 1, 2 and 4 months, we looked for plagiocephaly and collected information on the infants' environment.

Results

The environment of the Intervention group (n = 88) was significantly more favorable to unhindered movement than in the control group (n = 51) (lower immobility score, p < 0.01). The prevalence of DP was significantly lower in the Intervention group than in the control group (13% vs. 31%, p < 0.001). For each supplementary hour of immobility during the third and fourth months of life, the risk of DP at four months doubled (OR:2.1[1.4-3.2]).

Conclusion

Early postnatal intervention on the maternity ward reduces the prevalence of DP. The recent rise in the incidence of DP could be related to a lack of stimulation and encouragement to physical movement rather than to supine positioning proposed for prevention of sudden infant death syndrome.     

Sudden unexpected death in infancy: epidemiologically determined risk factors related to pathological classification

Infants that died suddenly and unexpectedly were studied as part of the European Concerted Action on sudden infant death syndrome (SIDS). Three paediatric pathologists, first independently of each other and later in a consensus meeting, classified 63 cases into 3 groups: SIDS (19 cases), borderline SIDS (30 cases) and non-SIDS (14 cases). The interobserver agreement among the pathologists before the consensus meeting was moderate (Kappa = 0.41) and jointly it was higher (Kappa = 0.83). The distribution of epidemiologically determined risk factors was studied over these three groups. Maternal smoking after birth, low socioeconomic status and thumb sucking were found more often in SIDS than in the other cases. Inexperienced prone sleeping was a determinant for SIDS, but not for non-SIDS. Previous hospital admission, low birthweight and/or short gestation were associated with borderline SIDS. Non-SIDS cases received more breastfeeding, the parents hardly smoked during pregnancy and after birth, a firm mattress had been used, and more often signs of illness had been reported by the parents, compared with the SIDS and borderline SIDS cases. Bedding factors and both primary and secondary prone sleeping were equally distributed over the three groups which supports the hypothesis that, in SIDS and borderline SIDS, as well as in non-SIDS cases, some similar external and preventable factors might influence the events leading to death. Research should therefore focus on all sudden unexpected deaths, after which subgroups such as SIDS cases can be separately analysed. The postmortem is an essential part of the whole work-up of each case and the results should be interpreted with all other available data to arrive at a sound evaluation of cases and thus form the basis for the prevention of all sudden unexpected infant death.     

Prone versus supine sleep position: a review of the physiological studies in SIDS research

A number of physiological studies, published over the last 10 years, have investigated the links between prone sleeping and sudden infant death syndrome (SIDS). This review evaluates those studies and derives an overview of the different affects of sleeping prone or supine in infancy. Generally, compared with the supine, the prone position raises arousal and wakening thresholds, promotes sleep and reduces autonomic activity through decreased parasympathetic activity, decreased sympathetic activity or an imbalance between the two systems. In addition, resting ventilation and ventilatory drive is improved in preterm infants, but in older infants (>1 month), there is no improvement in ventilation, and in 3-month-old infants, the position is adverse in terms of poorer ventilatory drive (in active sleep only). The majority of findings suggest a reduction in physiological control related to respiratory, cardiovascular and autonomic control mechanisms, including arousal during sleep in the prone position. Since the majority of these findings are from studies of healthy infants, continued reinforcement of the supine sleep recommendations for all infants is emphasized.     

Sudden infant death syndrome risk factors in north Queensland: a survey of infant-care practices in Indigenous and non-Indigenous women

OBJECTIVE: To assess the prevalence of sudden infant death syndrome (SIDS) risk factors in the Indigenous and non-Indigenous community of Townsville, a large remote urban centre in north Queensland, Australia. METHODS: Thirty Indigenous and 30 non-Indigenous women with young children were surveyed using sections of the West Australian Infancy and Pregnancy Survey 1997-1998. The prevalence of SIDS risk factors was compared between the two groups and medians and univariate associations were generated where appropriate. RESULTS: The Indigenous women were significantly younger and more likely to be single. The median age of the infants was 8 months (range 0.3-26 months) with no difference between the two groups. Thirty-seven per cent of Indigenous infants slept prone (cf. 17% of non-Indigenous infants; P = 0.03), and 77% shared a bed (cf. 13% of non-Indigenous infants; P < 0.001). The Indigenous households had significantly more members, with 57% including extended family members (cf. 20% non-Indigenous group; P = 0.003). Fifty-three per cent of the Indigenous women smoked during pregnancy (cf. 23% of non-Indigenous women; P = 0.017), 60% were smokers at the time of the interview, and smoking occurred inside 40% of Indigenous houses (cf. 20% and 20% for non-Indigenous women, respectively; P < 0.001, 0.09). CONCLUSION: This small survey suggests that the prevalence of SIDS risk factors is higher in the Indigenous population, and a new approach to education is needed urgently to promote SIDS awareness among Indigenous women.     

Prevention of sudden infant death syndrome (SIDS) due to an active health monitoring system 20 years prior to the public "Back to Sleep" campaigns

Background

Before reunification, the post‐neonatal mortality rate was lower in East Germany than in West Germany. Moreover, the incidence of SIDS (sudden infant death syndrome) was much lower in the East.

Methods

Mortality data on sudden infant death syndrome (SIDS) from West and East Germany since 1980 as well as post‐neonatal mortality data for both states since 1970 were examined. 95% Confidence intervals were calculated for the rates. Witnesses from the former East Germany who were involved at the time were also interviewed and archives were searched.

Results

We found that as early as 1972 active monitoring of infant and child mortality rates in East Germany had shown that the prone sleeping position was dangerous for infants: the post‐neonatal mortality rate was approximately 1 per 1000 live births lower in East than in West Germany during the 20 years before reunification. In contrast, in the West, prone sleeping was only discovered to be a risk factor for SIDS in the early 1990s.

Conclusions

Active monitoring is an effective tool in the early detection of risk factors and serves to prevent unnecessary deaths.     

Sudden infant death syndrome and sleeping position in pre-term and low birth weight infants: an opportunity for targeted intervention

Aims

To determine the combined effects of sudden infant death syndrome (SIDS) risk factors in the sleeping environment for infants who were “small at birth” (pre‐term (<37 weeks), low birth weight (<2500 g), or both).

Methods

A three year population based, case‐control study in five former health regions in England (population 17.7 million) with 325 cases and 1300 controls. Parental interviews were carried out after each death and reference sleep of age matched controls.

Results

Of the SIDS infants, 26% were “small at birth” compared to 8% of the controls. The most common sleeping position was supine, for both controls (69%) and those SIDS infants (48%) born at term or ⩾2500 g, but for “small at birth” SIDS infants the commonest sleeping position was side (48%). The combined effect of the risk associated with being “small at birth” and factors in the infant sleeping environment remained multiplicative despite controlling for possible confounding in the multivariate model. This effect was more than multiplicative for those infants placed to sleep on their side or who shared the bed with parents who habitually smoked, while for those “small at birth” SIDS who slept in a room separate from the parents, the large combined effect showed evidence of a significant interaction. No excess risk was identified from bed sharing with non‐smoking parents for infants born at term or birth weight ⩾2500 g.

Conclusion

The combined effects of SIDS risk factors in the sleeping environment and being pre‐term or low birth weight generate high risks for these infants. Their longer postnatal stay allows an opportunity to target parents and staff with risk reduction messages.