Seasonality of sudden infant death syndrome (SIDS) by age at death

Seasonality of sudden infant death syndrome (SIDS) is a well-established epidemiological finding. The purpose of the study was to determine whether this feature varied significantly with age at death. In total, 13 990 cases of SIDS in Scotland, England and Wales during 1982–1992 were studied by age group at death. Seasonality was established by fitting a sinusoidal curve and for each set of monthly data the peak position in the year and its magnitude were determined. Weighted regression revealed significant differences in peak position and amplitude of seasonal variation between those dying at ≤ 4 months and those aged ≥ 5 months at death. Those infants in the younger age group were more likely to die earlier in the winter months and had a smaller variation in seasonality. The peak (acrophase) months were January for ≤ 4 months and February for ≥ 5 months at death. Weighted regressions of peak position and amplitude on age at death had p-values of < 0.001 and < 0.01, respectively. A log linear model relating SIDS incidence to month of birth, month of death and age was able to explain some of these findings. The findings support the hypothesis that in SIDS there may be more than one infant cohort, each of which passes through a vulnerable developmental window at different ages.     

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.     

The airway occlusion test as a screening for sudden infant death syndrome (SIDS)

The airway occlusion test was carried out as a screening test for sudden infant death syndrome (SIDS). To obtain the normal values for use as control values, the relationship of the airway occlusion test with various variables was determined in 234 infants. The result shows that the best correlation was seen between percentage prolongation and the corrected gestational age. Percentage prolongation increased with the progression of age up to about the 40th week of corrected gestational age. Subsequently, there was no remarkable change in percentage prolongation. In six out of eight cases with apparent life threatening events, percentage prolongation was reduced. These results indicate that the determination of percentage prolongation can be used for screening of high risk babies for SIDS.     

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.     

The amount of brainstem gliosis in sudden infant death syndrome (SIDS) victims correlates with maternal cigarette smoking during pregnancy

Brainstem gliosis is elevated in some SIDS victims and has been associated with hypoxic-ischaemic events. Factors which increase the risk of SIDS include possible risk factors for hypoxic-ischaemic events during foetal and perinatal life. In this study a scoring system was developed whereby possible risk factors for hypoxic-ischaemic events during pregnancy, birth and in the perinatal period were correlated with the level of gliosis in the nucleus olivaris inferior in SIDS victims (n = 19). The mothers' antenatal care and obstetric records and the SIDS infants' perinatal hospital records were investigated, and each possible risk factor for hypoxic-ischaemic events was given one point. The points were summarized for each infant, and this sum was correlated with the level of gliosis in the infant's nucleus olivaris inferior. The number of cigarettes the mothers smoked during pregnancy was also compared with the level of gliosis. Our results show that in SIDS victims there is 41% probability that the more the mothers smoked during pregnancy, the more gliosis in the nucleus olivaris inferior is found in their infants (p < 0.01). Gliosis in the nucleus olivaris inferior also correlated with the possible risk factors for hypoxic-ischaemic events during pregnancy, birth and the perinatal period (r2 = 0.28, p < 0.05). However, if cigarette smoking was excluded as a possible hypoxic-ischaemic risk factor, no correlation was found.     

Pulmonary aspiration of gastric contents and the sudden infant death syndrome

OBJECTIVE: To determine ante-mortem and post-mortem risk factors for the finding of gastric contents in pulmonary airways (aspiration of gastric contents) at post-mortem examination in the sudden infant death syndrome (SIDS). METHODS: There were 217 post-neonatal deaths in the Auckland region of the New Zealand Cot Death Study. No deaths were certified as due to aspiration of gastric contents. There were 138 SIDS cases. The parents of 110 (80%) of these cases were interviewed. Histological sections from the periphery of the lungs in 99 of the 110 cases were reviewed for evidence of aspiration of gastric contents. A wide range of variables were analysed in SIDS cases with and without aspiration to determine risk factors. RESULTS: Aspiration of gastric contents was identified in 37 (37%) of SIDS cases. Aspiration was of mild-to-moderate degree and in no case was severe and a potential cause of death. Finding infants on their backs at death (P = 0.024) and conducting the post-mortem on the day after the death or subsequently (P = 0.033) were statistically significant variables linked to identification of aspiration. Position placed to sleep, symptoms of gastro-oesophageal reflux and other variables were not related to aspiration. CONCLUSIONS: The only determinants for aspiration of gastric contents identified were agonal or post-mortem events, supporting the contention that aspiration has limited relevance to the mechanism of SIDS.     

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.     

Metal content of the liver in sudden infant death syndrome

Abstract The metals zinc, iron, copper, manganese, calcium, magnesium, potassium and sodium were analysed in the livers of 67 Australian infants who had died from Sudden Infant Death Syndrome (SIDS) and 29 infants who had died from other causes (non-SIDS). The results were evaluated in relation to medical data and fatty acid composition of the livers. In infants less than 6 months old the liver potassium levels were significantly lower in SIDS than in non-SIDS infants. No other significant differences in metals between the SIDS and non-SIDS livers were found. Zinc, iron and copper levels in infant liver fell with age during the first year.     

Altered placental development in pregnancies resulting in sudden infant death syndrome (SIDS)

Background

Sudden infant death syndrome (SIDS) is postulated to be a developmental disorder originating during fetal life in utero. Knowledge regarding the intrauterine environment in which SIDS infants develop is, however, inadequate and how the placenta develops prior to a SIDS event has not been studied.

Aim

To investigate the morphological development of the placenta obtained from full-term infants who subsequently succumbed to SIDS.

Study design

To estimate the percentage and total volumes of the chorionic villi and villous trophoblast membrane using stereological techniques.

Subjects

Placentas were obtained retrospectively from normal birthweight (SIDS-NBW n = 18) and small-for-gestational age (SIDS-SGA, n = 14) infants who had succumbed to SIDS, and compared to either control (n = 8) or SGA placentas (n = 7), respectively.

Results

SIDS-NBW placentas displayed evidence of augmented villous growth shown by significantly greater volumes of placental chorionic villi (gas-exchanging (GE) villi) in comparison to controls; this was not observed for SIDS-SGA placentas. However, both SIDS-NBW and SIDS-SGA placentas displayed significantly greater volumes of the cytotrophoblast (CT) (SIDS-NBW only), syncytiotrophoblast (SIDS-SGA only) and syncytial knots (SCT-K) and those displaying apoptotic syncytial nuclei (AP SCT-K). In contrast, SGA placentas displayed significantly reduced volumes of chorionic villi, GE villi and the villous trophoblast indicating a SIDS-specific effect associated with augmented placental growth.

Conclusions

Our findings provide initial evidence that placental abnormality, although not necessarily causative, may precede a subset of SIDS cases supporting the hypothesis that the origins of SIDS begin during fetal life in utero.     

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.     

Growth and the sudden infant death syndrome

Objective : To compare the growth curves based on measurements of body weight for male and female infants dying of sudden infant death syndrome (SIDS) with those of male and female controls. Methods : The data were drawn from a large case control study of SIDS carried out in New Zealand between 1987 and 1990. Results : The mean birthweight for the cases was 3049 g and for the controls 3526 g. The mean growth curves for the male and female controls were close to the 50th centile of growth charts used in New Zealand. The growth curve for the male cases diverged from that of the controls, being closer to the 25th percentile. The differences between the female cases and controls were less pronounced. The differences in weekly weight increments derived from the curves for the cases and controls for nine 4-week periods were not statistically significant after taking into account race, manner of feeding and maternal smoking for any 4-week period. Conclusions : SIDS cases were lighter at birth, but their growth velocity was normal postnatally.     

Epidemiology of sudden infant death syndrome in Japan

An epidemiological survey was carried out to examine the present situation with respect to sudden infant death syndrome (SIDS) in Kanagawa Prefecture. Questionnaires on sudden unexpected death of infants aged < 1 year in 1990-91 were sent to the hospitals and clinics in Kanagawa Prefecture which may take care of such infants. By analysing information from 10 485 replies, 48 out of 73 reported sudden infant deaths were confirmed to be SIDS, although autopsy was not performed in 13 cases (27%). The incidence of SIDS per 1000 live births in Kanagawa Prefecture was 0.29 in 1990 and 0.31 in 1991; and if limited to autopsy cases 0.19 and 0.25, respectively. Sudden infant death syndrome cases in Japan were found to occur more frequently when infants were < 6 months old, at home and sleeping alone, but less in the winter and between midnight and early morning. There was little difference between the numbers in prone and supine sleeping positions at discovery. It was not clear whether SIDS occurred more often to babies sleeping prone than supine, because there were no controls matched with the SIDS cases. In future, continuous epidemiological surveys of SIDS in Japan should be carried out.     

Investigation of unexplained infant deaths in Jerusalem, Israel 1996-2003

Background

Sudden infant death syndrome (SIDS) is a diagnosis of exclusion that may be assigned only after investigations including a forensic autopsy are performed to exclude possible organic and environmental causes of death. Israeli society is influenced by the Jewish and Islamic faiths, which permit autopsy only under selected circumstances. Against this background, we carried out a study to determine what examinations are performed to investigate unexplained infant deaths in Jerusalem, Israel.

Methods

We examined hospital, Ministry of Health and Ministry of Interior records of unexplained infant deaths in the Jerusalem district from the years 1996–2003.

Results

Ninety six cases were identified from all sources. Forty nine (51%) infants were brought to a hospital at or near the time of death. Studies to determine the cause of death were performed in 54% of cases for which medical records were available for review. These studies included bacterial cultures (44%), skeletal surveys (12%), computerised tomography (3%) and metabolic studies (3%). Only one forensic autopsy was performed, and in no instance was the death site examined by medical personnel. There was a high rate of retrospective review by district health physicians. The most frequently assigned cause of death was SIDS.

Conclusions

: The capacity of public health officials and forensic pathologists to investigate unexplained infant deaths is strongly affected by the legal, religious and political milieu in which they work. Efforts should be made to develop socially acceptable methods of improving the quality of infant death investigations in Jerusalem.     

Issues in diagnosis following the sudden infant death syndrome intervention campaigns

Abstract: The fall in numbers of sudden infant death syndrome (SIDS) deaths in recent years has resulted in questions being asked as to whether changes in the pathological assessment and diagnosis of such cases have influenced reported death rates. Specific concerns have been raised about possible changes in diagnostic criteria, differences in the evaluation of these infants and the possibility of changes in the pathological findings at autopsy. However, no major changes in either diagnostic criteria or in pathological features appear to have occurred, despite some changes in the epidemiological characteristics of cases.     

Home monitoring for infants at risk of the sudden infant death syndrome

Abstract This study evaluates the effectiveness and social implications of home monitoring of 31 infants at risk of sudden infant death syndrome (SIDS). Thirteen siblings of children dying of SIDS, nine near miss SIDS infants and nine preterm infants with apnoea persisting beyond 40 weeks post conceptual age were monitored from a mean age of 15 days to a mean of 10 months. Chest movement detection monitors were used in 27 and thoracic impedance monitors in four. Genuine apnoeic episodes were reported by 21 families, and 13 infants required resuscitation. Apnoeic episodes occurred in all nine preterm infants but in only five (38%) of the siblings of SIDS (P<0.05). Troublesome false alarms were a major problem occurring with 61% of the infants and were more common with the preterm infants than the siblings of SIDS. All but two couples stated that the monitor decreased anxiety and improved their quality of life. Most parents accepted that the social restrictions imposed by the monitor were part of the caring process but four couples were highly resentful of the changes imposed on their lifestyle.
The monitors used were far from ideal with malfunction occurring in 17, necessitating replacement in six, repair in six and cessation of monitoring in three. The parents became ingenious in modifying the monitors to their own individual requirements
Although none of these 31 'at risk' infants died the study sample was far too small to conclude whether home monitoring prevented any cases of SIDS.     

Near miss sudden death in an infant with Wolff-Parkinson-White syndrome

A 6 month old infant with known Wolff-Parkinson-White syndrome presented with an out of hospital cardiac arrest. An electrocardiogram in the emergency department demonstrated atrial fibrillation with rapid ventricular response. The child subsequently was resuscitated and underwent successful interruption of an accessory connection after failing medical therapy. This case underlines the need to reassess the indications for invasive electrophysiologic testing in young children.     

Overview of sudden infant death syndrome in Japan

In spite of rapid medical advancement in the care of infants and children, not only the general public but also many medical personnel have remained unaware of sudden infant death syndrome (SIDS) until very recently in Japan. In 1981, a research project team on SIDS financed by the Ministry of Health and Welfare was founded. Current incidence of SIDS is estimated to be about 0.5 per 1000 live births. The SIDS Family Association was organized in 1993 in Japan and began to publicize the social importance of SIDS and to support SIDS families by training befrienders. A series of articles on current achievements from SIDS research projects and from the SIDS Family Association are submitted to this issue. The present paper summarizes the status of SIDS in Japan by overviewing the activities of the research team and the SIDS Family Association.     

Gender and the sudden infant death syndrome

Abstract A nationwide case-control study compared the prevalence and magnitude of risk factors for sudden infant death syndrome (SIDS) in male and female infants. The risk factors of SIDS and their magnitude for males and females are very similar. After adjustment for potential confounders male infants had a 1.42-fold (95% CI = 1.04, 1.94) increased risk of SIDS compared with females. Risk factors identified in most epidemiological studies are not the reason for the increased SIDS mortality seen in male infants.     

Dummy (pacifier) use and sudden infant death syndrome: Potential advantages and disadvantages

The large decline in deaths due to the sudden infant death syndrome (SIDS) in the last 20 years in many countries is largely due to risk‐reduction advice resulting from observational studies that examined the relationship between infant care practices and SIDS. Most of this advice remains largely uncontroversial and educators and researchers in this field are in agreement as to the specific recommendations that should be given to parents and health professionals. However, advice surrounding the apparent protective effect of dummies (also known as pacifiers) has been controversial. Several systematic reviews have demonstrated a strong association between the lack of a pacifier being used by the infant for the final sleep and SIDS, but it is not clear how pacifiers confer protection or if this is a marker for something as yet unmeasured. The Epidemiology and Physiology Working Groups of the International Society for the Study and Prevention of Perinatal and Infant Death (ISPID) are comprised of leading SIDS researchers with an objective to provide evidence‐based position statements surrounding the factors associated with SIDS ( http://www.ispid.org/ ) and risk‐reduction strategies. The evidence, discussion and conclusions from these working groups regarding dummies (pacifiers) are described below to help inform this debate and describe the future evidence required so that we might find a common recommendation about dummies (pacifiers) and SIDS.