Four modifiable and other major risk factors for cot death: the New Zealand study

The role of gastro-oesophageal reflux in the aetiology of SIDS

Gastro-oesophageal reflux (GOR) has been identified as a possible cause of SIDS. Several features of GOR unique to infants presenting with apparent life-threatening events (ALTEs) have led to its 'pathogenic' definition. One is that the life-threatening apnoea itself is initiated by GOR, another is that the ALTE relates to prolonged reflux during sleep, in a vulnerable sleep-state, and finally that the ALTE relates to excessive quantities of GOR. The presumption of GOR 'pathology' as a cause of SIDS however, is questionable in these susceptible infants for three reasons: firstly, GOR is physiological and occurs in most infants; secondly, there is no general consensus on what constitutes normal physiological reflux, and thirdly, variation in the recording technique and methods of data analysis and interpretation may account for the differences between study groups. It seems likely therefore if GOR is implicated in SIDS, additional factors are involved. Under certain circumstances, physiological GOR may trigger life-threatening apnoea in apparently healthy infants, that leads to SIDS. One mechanism that could explain such a death is reflex apnoea by stimulation of laryngeal chemoreceptors (LCR) during sleep. The conditions under which this could be fatal are the occurrence of gastric contents refluxed to the level of the pharynx during sleep, in the young infant who has depressed swallowing and arousal. That is, the occurrence of GOR to the level of the pharynx during sleep, an infrequent event that is usually innocuous, could be converted to a fatal event if swallowing is impaired and arousal depressed, by a variety of mediating factors such as prone sleeping, prematurity, sedatives, seizures or upper respiratory tract infections. The identification of LCR responses, particularly in prone sleeping and premature infants provide further evidence that this mechanism may be implicated in the aetiology of SIDS in apparently healthy infants.

Perinatal complications associated with maternal tobacco use

The use of tobacco products by pregnant women is associated with placenta previa, abruptio placentae, premature rupture of the membranes, preterm birth, intrauterine growth restriction and sudden infant death syndrome. Approximately 15-20% of women smoke during pregnancy. It has been suggested that smoking is responsible for 15% of all preterm births, 20-30% of all infants of low birthweight, and a 150% increase in overall perinatal mortality. Cigarette smoking is one of the most important and modifiable risk factors associated with adverse perinatal outcomes.

Deprivation and sudden infant death syndrome

This research uses a case-control study to examine the relationship between deprivation of area of residence and incidence of sudden infant death syndrome (SIDS) in New Zealand. Three hundred sixteen cases and 1221 controls were elicited with geocodable addresses. Infants living in the most deprived areas had a 5.9- (95%CI = 2.9, 12.2) fold increased risk of SIDS compared with those infants living in the least deprived areas. After adjusting for individual-level factors there was no remaining area-level effect. Nearly 27% of control infants lived in the two lowest deciles of deprivation, and almost half of SIDS deaths occurred in these areas. Incidence of SIDS is strongly associated with both deprivation of area of residence and individual socioeconomic factors. This indicates the importance of reaching parents in deprived areas, however, given that approximately 50% of SIDS deaths occurred in areas other than the two most deprived, we recommend that SIDS health messages be delivered to the general population.

Bed sharing patterns in a cohort of Australian infants during the first six months after birth

OBJECTIVE

To measure bed sharing (BS) activity in healthy term infants.

METHODOLOGY

The sleep-wake behaviour and place of infant sleep were recorded for infants aged between 2 and 24 weeks. Infants were then identified as BS or non bed sharing (NBS) according to each of four different definitions of bed sharing.

RESULTS

The mean proportion of infants who spent any time BS during a 24-h period was significantly greater (P < 0.05) between 2 and 12 weeks (40.9 +/- 1. 4%) than between 13 and 24 weeks (36.5 +/- 1.5%). A significantly greater proportion (P < 0.005) of infants bed shared for more than 2 h (25 +/- 1%) than for either 1-2 h (10.5 +/- 1.1%) or for less than 1 h/24 h (3.2 +/- 0.5%) during the whole study period. Each of the definitions of BS used in the study separated infants on the basis of the amount and frequency of BS activity.

CONCLUSION

: Bed sharing activity was common and varied in this cohort. It was possible, using quantitative definitions, to identify those infants who routinely bed share.

Age-dependent metabolic effects of repeated hypoxemia in piglets

The aim of this study was to determine whether repeated exposure to hypoxemia would modify the response to hypoxemia during maturation. We exposed piglets to three 1-h cycles of hypoxemia (PaO2 = 30 to 35 mmHg; 1 mmHg = 133.3 Pa) at 1 week (n = 9), 2-3 weeks (n = 10), and 4-5 weeks of age (n = 10). O2 consumption (VO2) and CO2 production (VCO2) were measured, and alveolar ventilation (VA) was derived from VCO2 and PaCO2. Levels of lactic acid (lactate) and serum catecholamines were also measured. With hypoxemia, time had a significant effect on VO2 and body temperature in an age-dependent fashion: that is, whereas the 1 week group and the 4-5 week group showed both variables decreasing over time, the 2-3 week group showed no drop in VO2 and a small increase in body temperature over time. Lactate levels increased with hypoxemia in all animals during the first exposure. However, with repeated exposures to hypoxemia, only the 2-3 week group continued to increase its lactate levels. Furthermore, the changes in lactate levels paralleled the changes in epinephrine levels with hypoxemia. We found, too, that although VA increased significantly with hypoxemia in all animals, this change was not modified by age or repeated exposures. No significant effects of age or repeated exposures were found in the cardiovascular response to hypoxemia. We concluded that, from a metabolic viewpoint, after repeated exposures to hypoxemia the 2-3 week animals responded differently.Key words: metabolic rate, lactic acid, maturation, catecholamines.

The role of breastfeeding in sudden infant death syndrome

The objective of this article is to review the literature regarding the risk of sudden infant death syndrome (SIDS) in bottle-fed infants compared to those that are breastfed. A meta-analysis and qualitative literature review were performed. Cohort and case-control studies were included if they met a minimum SIDS definition and presented data allowing calculation of an odds ratio (OR). Twenty-three studies were included in the meta-analysis. The studies were heterogeneous, and a majority (14) were of "fair" or "poor" quality. Crude ORs from 19 individual studies favored breastfeeding as protective against SIDS. The combined analysis indicated that bottle-fed infants were twice as likely to die from SIDS (pooled OR = 2.11; 95% CI 1.66-2.68). The results of the analysis show that there is an association between bottle-feeding and SIDS, but this may be related to confounding variables.

Natural selection and sex differences in morbidity and mortality in early life

Both morbidity and mortality are consistently reported to be higher in males than in females in early life, but no explanation for these findings has been offered. This paper argues that the sex difference in early vulnerability can be attributed to the natural selection of optimal maternal strategies for maximizing lifetime reproductive success, as modelled previously by Trivers and Willard. These authors theorized that males and females offer different returns on parental investment depending on the state of the environment. Natural selection has therefore favoured maternal ability to manipulate offspring sex in response to environmental conditions in early life, as shown in variation in the sex ratio at birth. This argument can be extended to the whole period of parental investment until weaning. Male vulnerability in response to environmental stress in early life is predicted to have been favoured by natural selection. This vulnerability is most evident in the harsh conditions resulting from pre-term birth, but can also be seen in term infants, and manifests as greater morbidity and mortality persisting into early childhood. Malnutrition, interacting with infection after birth, is suggested as the fundamental trigger mechanism. The model suggests that whatever improvements are made in medical care, any environmental stress will always affect males more severely than females in early life.

Babies sleeping with parents: case-control study of factors influencing the risk of the sudden infant death syndrome. CESDI SUDI research group

OBJECTIVE

To investigate the risks of the sudden infant death syndrome and factors that may contribute to unsafe sleeping environments.

DESIGN

Three year, population based case-control study. Parental interviews were conducted for each sudden infant death and for four controls matched for age, locality, and time of sleep.

SETTING

Five regions in England with a total population of over 17 million people.

SUBJECTS

325 babies who died and 1300 control infants.

RESULTS

In the multivariate analysis infants who shared their parents' bed and were then put back in their own cot had no increased risk (odds ratio 0.67; 95% confidence interval 0.22 to 2.00). There was an increased risk for infants who shared the bed for the whole sleep or were taken to and found in the parental bed (9.78; 4.02 to 23.83), infants who slept in a separate room from their parents (10.49; 4.26 to 25.81), and infants who shared a sofa (48.99; 5.04 to 475.60). The risk associated with being found in the parental bed was not significant for older infants (>14 weeks) or for infants of parents who did not smoke and became non-significant after adjustment for recent maternal alcohol consumption (>2 units), use of duvets (>4 togs), parental tiredness (infant slept </=4 hours for longest sleep in previous 24 hours), and overcrowded housing conditions (>2 people per room of the house).

CONCLUSIONS

There are certain circumstances when bed sharing should be avoided, particularly for infants under four months old. Parents sleeping on a sofa with infants should always be avoided. There is no evidence that bed sharing is hazardous for infants of parents who do not smoke.

Use of duvets and the risk of sudden infant death syndrome

BACKGROUND

The use of duvets in infancy is not recommended in the UK and Australia because of a reported association with sudden infant death syndrome (SIDS).

AIMS

To examine the association between the use of duvets and the risk of SIDS.

METHODS

A nationwide case control study (393 cases, 1592 controls). The use of duvets was assessed by interview with the parent or guardian.

RESULTS

The use of duvets was associated with an increased risk of SIDS (odds ratio (OR) = 1.65; 95% confidence interval (CI), 1.31 to 2.08); however, after adjustment for potential confounders there was no increased risk of SIDS (OR = 1.04; 95% CI, 0.77 to 1.38). Furthermore, subgroup analysis did not identify any group in which the use of duvets was associated with an increased risk of SIDS.

CONCLUSIONS

This study does not support the recommendation to avoid duvets.

Sudden infant death syndrome, virus infections and cytokines

Many epidemiological risk factors identified for sudden infant death syndrome (SIDS) suggest a viral aetiology, e.g. exposure to cigarette smoke and winter peak, mild respiratory symptoms. Virus infections and bacterial toxins induce cytokine activity and it has been suggested that uncontrolled inflammatory mediators could be involved in some cases of SIDS. The aim of this review was to assess the evidence for virus infection in SIDS and to examine those findings in relation to individual variations in cytokine responses and various pathophysiological mechanisms proposed for SIDS such as sleep derangement, hypoxia, cardiac arrhythmia, vascular hypotonicity and hypoglycaemia.

Short-term morbidity and infant mortality among infants who slept supine at 1 month of age--a follow-up report

Following evidence that prone sleeping is causally related to sudden infant death syndrome (SIDS), intervention campaigns to avoid prone sleeping in many countries have led to a large reduction in SIDS and total infant mortality. The supine position has been recommended for healthy infants in several countries. The objective of this report was to determine how usual sleep position at 1 month relates to morbidity indicators at 1 month and 12 weeks and to SIDS and postneonatal mortality using a prospective population-based live birth cohort in Tasmania, Australia. Eligible infants were the one-fifth of Tasmanian live births at higher risk of SIDS using a perinatal score. From 1 January 1988 to 31 December 1995, 9826 (89% of eligible) infants participated in the home interview. Fifty-three eligible infants died of SIDS, 51 (96%) with hospital interview data and 35 (81% of those eligible for home visit) with home visit data. The main outcome measures were SIDS, postneonatal mortality and parentally reported infant morbidity. The postneonatal mortality rates (cases per 1000 live births) by usual sleep position at 1 month of age were supine 1.60 [95% CI 0.04, 8.87], side 2.87 [1.79, 4.35], prone 10.27 [5.62, 17.18] and other (including no usual position) 6.37 [0.16, 34.98]. None of the study infants who slept supine died of SIDS at a later time. Of 25 morbidity indicators studied, only noisy breathing was increased for supine compared with side-sleeping babies. In this study, there was no evidence to suggest that supine sleeping at 1 month of age was associated with an increase in important short-term morbidity or postneonatal mortality. These findings provide further support for the recent recommendations of the American Academy of Pediatrics that healthy infants should preferably sleep in the supine position.

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.

Sheepskin bedding and the sudden infant death syndrome. New Zealand Cot Death Study Group

We carried out a nationwide case-control study, comparing 393 case patients with sudden infant death syndrome (SIDS) with 1592 control subjects, in order to examine sheepskin bedding as a risk factor. Sheepskin use was similar for case patients and control subjects (both, 42%; adjusted odds ratio [OR] = 1.28; 95% CI = 0.92, 1.79). Sheepskin use among the control subjects was associated with socioeconomic advantage. The relative risk for SIDS with sheepskin use was significantly increased in the infants placed prone to sleep (adjusted OR = 1.70; 95% CI = 1.08, 2.67), but not for infants placed in the supine or lateral position (adjusted OR = 0.82; 95% CI = 0.45, 1.48). An interaction between sheepskin use and bed sharing was also found. Sheepskin use was associated with a decreased risk of SIDS among infants sharing beds (adjusted OR = 0.61; 95% CI = 0.38, 0.99), but an increased risk among infants not bed sharing (adjusted OR = 2.25; 95% CI = 1.32, 3.86). We conclude that if an infant needs to be placed prone to sleep for medical reasons, a sheepskin should not be used as underbedding. However, for infants placed supine to sleep, sheepskins are not associated with an increased risk of SIDS.

Residential mobility and sudden infant death syndrome

OBJECTIVE

To examine whether permanent domicile change of the mother, thence the infant, or temporary relocation of the infant away from his or her usual place of residence affects the risk of sudden infant death syndrome (SIDS).

DESIGN

A case-control nation-wide epidemiological study.

SETTING

New Zealand between the years 1987-90.

PARTICIPANTS

From the 485 SIDS diagnoses over this time, parents of 393 (81%) SIDS infants consented to participate and these comprise the cases. Controls were selected by randomly sampling 1800 infants from all babies born over 78% of the country. Parents of 1592 (88%) control infants participated.

RESULTS

Infants away from their usual address were 1.70 (95% CI: 1.09, 2.66) times more likely to die from SIDS than infants sleeping at home, after controlling for likely confounding factors. A partial explanation for this finding was that SIDS infants were less likely to have been mainly breast fed in the last two days and were less likely to have shared a room with at least one adult at the nominated sleep/death. Infants of mothers who shifted house after their birth, infants having mothers who shifted house within a year prior to the study interview date, and infants who slept at numerous different houses were associated with an increased relative risk for SIDS at the univariate level, but not after adjustment.

CONCLUSIONS

Infants are less likely to die in their accustomed residential environment. This finding needs confirmation by other studies.

Side sleeping position and bed sharing in the sudden infant death syndrome

In the last decade there have been major reductions in the sudden infant death syndrome (SIDS) rate following prevention programmes in Australasia, Europe and North America, mainly due to changing infants from the prone sleeping position onto their sides or backs. This report reviews previous SIDS observational studies with data on side sleeping position and bed sharing. The relative risk for SIDS calculated from previous studies for side vs back sleeping position is 2.02 (95% CI = 1.68, 2.43). This result suggests that further substantial decreases in SIDS could be expected if infants were placed to sleep on their backs. With regard to bed sharing, the summary SIDS relative risk is 2.06 (1.70, 2.50) for infants of smoking mothers and 1.42 (1.12, 1.79) for infants of nonsmoking mothers. Public health policy should be directed against bed sharing by infants whose mothers smoke as they carry an increased risk of SIDS from bed sharing in addition to their already increased risk from maternal smoking. For infants of nonsmoking mothers, who have a low absolute risk of SIDS, the 40-50% increase in risk needs to be balanced against other perceived benefits from bed sharing, such as increased breastfeeding.

Prolongation of the QT interval and the sudden infant death syndrome

BACKGROUND

The sudden infant death syndrome (SIDS) is multifactorial in origin, but its causes remain unknown. We previously proposed that prolongation of the QT interval on the electrocardiogram, possibly resulting from a developmental abnormality in cardiac sympathetic innervation, may increase the risk of life-threatening ventricular arrhythmias and contribute to this devastating disorder. We prospectively tested this hypothesis.

METHODS

Between 1976 and 1994, we recorded electrocardiograms on the third or fourth day of life in 34,442 newborns and followed them prospectively for one year. The QT interval was analyzed with and without correction for the heart rate.

RESULTS

One-year follow-up data were available for 33,034 of the infants. There were 34 deaths, of which 24 were due to SIDS. The infants who died of SIDS had a longer corrected QT interval (QTc) than did the survivors (mean [+/-SD], 435+/-45 vs. 400+/-20 msec, P<0.01) and the infants who died from causes other than SIDS (393+/-24 msec, P<0.05). Moreover, 12 of the 24 SIDS victims but none of the other infants had a prolonged QTc (defined as a QTc greater than 440 msec). When the absolute QT interval was determined for similar cardiac-cycle lengths, it was found that 12 of the 24 infants who died of SIDS had a QT value exceeding the 97.5th percentile for the study group as a whole. The odds ratio for SIDS in infants with a prolonged QTc was 41.3 (95 percent confidence interval, 17.3 to 98.4).

CONCLUSIONS

Prolongation of the QT interval in the first week of life is strongly associated with SIDS. Neonatal electrocardiographic screening may permit the early identification of a substantial percentage of infants at risk for SIDS, and the institution of preventive measures may therefore be possible.

Epidemiology of intrathoracic petechial hemorrhages in sudden infant death syndrome

The possible effects of a wide range of sociodemographic and environmental factors on the incidence and distribution of petechiae were investigated in 485 sudden infant death syndrome (SIDS) cases from the New Zealand Cot Death Study. The number (nil, few, many) of macroscopic petechial hemorrhages in the visceral pleura, capsule of thymus, and epicardium was recorded in 458 of 474 autopsied SIDS cases. Other information was obtained from parental interview and obstetric records. Univariate analysis showed highly significant relationships (P < or = 0.005) between the frequency of petechiae at one or more sites and socioeconomic status, parity, breast feeding, age at death, time of death, sleep position, and head covering at death and lesser but significant relationships (P < or = 0.05) with Maori ethnicity, birth weight, gestation, pacifier use, and bed sharing. After multivariate analysis, significant associations remained between increased frequencies of thymic petechiae and parity (P = 0.0001), age at death (P = 0.0003), Maori ethnicity (P = 0.0019), pacifier use (P = 0.0001), and head covering at death (P = 0.0032); between increased frequencies of epicardial petechiae and head covering at death (P = 0.008) and an estimated time of death between 00:00 and 05:59 h (P = 0.056); and between increased frequencies of pleural petechiae and maternal smoking (P = 0.058) and parity (P = 0.022). There was a decreased frequency of pleural petechiae in infants placed prone for their final sleep (P = 0.058). The distribution and frequency of petechiae are affected by environmental factors, including known risk factors for SIDS, but these factors occur inconsistently across the three sites. The findings imply differences in the pathogenesis at each site but do not provide consistent support for previous theories of causation of petechiae.

The changing epidemiology of SIDS following the national risk reduction campaigns

Prone sleeping position is causally associated with SIDS. The change in the proportion of infants sleeping prone has resulted in a dramatic reduction in SIDS and total postneonatal mortality. The effect of prone sleeping position is modified by season, latitude, illness, thermal insulation and sheepskins. This suggests that the mechanism by which prone sleeping position causes SIDS is in some way related to temperature.

Heavy caffeine intake in pregnancy and sudden infant death syndrome. New Zealand Cot Death Study Group

AIMS

To examine the association between maternal caffeine consumption during pregnancy and the risk of sudden infant death syndrome (SIDS).

METHODS

A nationwide case-control study surveying parents of 393 SIDS victims and parents of 1592 control infants. Caffeine consumption in each of the first and third trimesters was estimated by questionnaire. Heavy caffeine intake was defined as 400 mg/day or more (equivalent to four or more cups of coffee per day).

RESULTS

Infants whose mothers had heavy caffeine consumption throughout their pregnancy had a significantly increased risk for SIDS (odds ratio 1.65; 95% confidence interval 1.15 to 2.35) after adjusting for likely confounding factors.

CONCLUSION

Caffeine intake has been associated with fetal harm and now SIDS. Reducing heavy caffeine intake during pregnancy could be another way to lessen the risk of SIDS. This needs confirmation by others.

Breastfeeding and the use of human milk. American Academy of Pediatrics. Work Group on Breastfeeding

This policy statement on breastfeeding replaces the previous policy statement of the American Academy of Pediatrics, reflecting the considerable advances that have occurred in recent years in the scientific knowledge of the benefits of breastfeeding, in the mechanisms underlying these benefits, and in the practice of breastfeeding. This document summarizes the benefits of breastfeeding to the infant, the mother, and the nation, and sets forth principles to guide the pediatrician and other health care providers in the initiation and maintenance of breastfeeding. The policy statement also delineates the various ways in which pediatricians can promote, protect, and support breastfeeding, not only in their individual practices but also in the hospital, medical school, community, and nation.

Passive smoking and sudden infant death syndrome: review of the epidemiological evidence

BACKGROUND

This paper provides a systematic, quantitative review of the epidemiological evidence relating parental smoking and sudden infant death.

METHODS

Thirty two relevant publications were identified after consideration of 692 articles selected by electronic search of the Embase and Medline databases using keywords and Mesh headings relevant to passive smoking in children. Eleven further articles were identified from reviews and by talking to authors. The search was completed in April 1997 and identified 39 studies.

RESULTS

The unadjusted pooled odds ratio for prenatal maternal smoking was 2.77 (95% CI 2.45 to 3.13). After adjustment for a variety of confounders the pooled odds ratio was reduced to 2.08 (95% CI 1.83 to 2.38) and was similar in cohort and case-control studies. Four studies reported on maternal postnatal smoking after controlling for prenatal maternal smoking (pooled odds ratio 1.94 (95% CI 1.55 to 2.43)). Of three studies reporting on the risk of paternal smoking where the mother was a non-smoker, two found significant effects while one found no effect. Dose-response relationships with both prenatal and postnatal maternal smoking were present in most studies which provided data.

CONCLUSIONS

Maternal smoking doubles the risk of sudden infant death syndrome. The relationship is almost certainly causal. There is good evidence that postnatal exposure to environmental tobacco smoke from both mother and father are important. Because prenatal smoking is almost invariably associated with postnatal smoking, the role of prenatal smoking per se will be difficult to resolve using epidemiological studies.

Risk factors for sudden infant death syndrome following the prevention campaign in New Zealand: a prospective study

OBJECTIVES

To identify the risk factors for sudden infant death syndrome (SIDS) following a national campaign to prevent SIDS.

METHODS

For 2 years (October 1, 1991 through September 30, 1993) data were collected by community child health nurses on all infants born in New Zealand at initial contact and at 2 months.

RESULTS

There were 232 SIDS cases in the postneonatal age group (2.0/1000 live births) and these were compared with 1200 randomly selected control subjects. Information was available for 127 cases (54.7%) and 922 (76.8%) of controls. The previously identified modifiable risk factors were examined. The prevalence of prone sleeping position of the infant was very low (0.7% at initial contact and 3. 0% at 2 months), but was still associated with an increased risk of SIDS. In addition, the side sleeping position was also found to have an increased risk of SIDS compared with the supine sleeping position (at 2 months: adjusted odds ratio (OR) = 6.57; 95% confidence interval (CI) = 1.71, 25.23). Maternal smoking was found to be the major risk factor for SIDS. Bed sharing was also associated with an increased risk of SIDS. There was an interaction between maternal smoking and bed sharing on the risk of SIDS. Compared with infants not exposed to either bed sharing or maternal smoking, the adjusted OR for infants of mothers who smoked was 5.01 (95% CI = 2.01, 12.46) for bed sharing at the initial contact and 5.02 (95% CI = 1.05, 24. 05) for bed sharing at 2 months. In this study breastfeeding was not associated with a statistically significant reduction in the risk of SIDS. The other risk factors for SIDS identified were: unmarried mother, leaving school at a younger age, young mother, greater number of previous pregnancies, late attendance for antenatal care, smoking in pregnancy, male infant, Maori ethnicity, low birth weight, and shorter gestation.

CONCLUSIONS

After adjustment for potential confounders, prone and side sleeping positions, maternal smoking, and the joint exposure to bed sharing and maternal smoking were associated with statistically significant increased risk of SIDS. A change from the side to the supine sleeping position could result in a substantial reduction in SIDS. Maternal smoking is common in New Zealand and with the reduction in the prevalence of prone sleeping position is now the major risk factor in this country. However, smoking behavior has been difficult to change. Bed sharing is also a major factor but appears only to be a risk to infants of mothers who smoke. Addressing bed sharing among mothers who smoke could reduce SIDS by at least one third. Breastfeeding did not appear to offer a statistically significant reduction in SIDS risk after adjustment of potential confounders, but as breastfeeding rates are comparatively good in New Zealand, this result should be interpreted with caution as the power of this study to detect a benefit is small.

Infant arousals during mother-infant bed sharing: implications for infant sleep and sudden infant death syndrome research

OBJECTIVE

Normative values for infant sleep architecture have been established exclusively in the solitary sleeping environment. However, most of the world's cultures practice some form of parent-infant cosleeping. In addition, no previous polysomnographic studies in infants examined the frequency of electroencephalogram (EEG) arousals. This is the first study to assess (a) EEG arousals in infants and their relationship to sleep stages; (b) the impact on arousals of mother-infant bed sharing; and (c) the temporal overlap of infant with maternal arousals during bed sharing.

METHODOLOGY

Three nights of polysomnography were performed in 35 breastfeeding mother-infant pairs when the infants were 11 to 15 weeks old. An adaptation night was followed by one bed sharing night and one solitary sleeping night. Twenty infants had been bed sharing since birth and 15 were routine solitary sleepers. Both epochal awakenings (EWs), based on 30-second epoch scoring of sleep-wake stages, and more transient arousals (TAs) >/=3 seconds were quantified.

RESULTS

Stage 3-4 sleep was associated with a striking paucity of EWs and TAs compared with stages 1-2 or rapid eye movement sleep. Bed sharing facilitated EWs and TAs selectively during stage 3-4 sleep. EWs from stage 3-4 sleep were more frequent on the bed sharing night than on the solitary night in both infant groups. Routinely bed sharing infants also exhibited more frequent TAs in stage 3-4 than the routine solitary sleepers in both conditions. In both groups, the number of infant arousals (EWs + TAs) that overlapped the mother's was doubled during bed sharing, with infant arousals leading most often.

CONCLUSIONS

Mother-infant bed sharing promotes infant arousals. Together with a previous report that bed sharing reduces stage 3-4 sleep, this suggests that normative values for infant sleep must be interpreted within the context of the sleeping environment in which they were established. Given that arousability is diminished in stage 3-4, we speculate that, under otherwise safe conditions, the observed changes in stage 3-4 sleep and arousals associated with bed sharing might be protective to infants at risk for SIDS because of a hypothesized arousal deficit. The responsivity of the mother to infant arousals during bed sharing might also be protective.

Combined effects of sleeping position and prenatal risk factors in sudden infant death syndrome: the Nordic Epidemiological SIDS Study

OBJECTIVE

Prone sleeping is a strong risk factor for sudden infant death syndrome (SIDS). We investigated whether the combined effect of prone sleeping position and prenatal risk factors further increased the SIDS risk.

METHODS

In the Nordic Epidemiological SIDS Study, parents of SIDS victims in Denmark, Norway, and Sweden completed a questionnaire on potential risk factors for SIDS. Forensic pathologists verified the SIDS diagnosis. Four controls of the same gender, age, and place of birth were selected. This matched case-control study, which included 244 SIDS cases and 869 controls from 1992 to 1995, was analyzed by conditional logistic regression.

RESULTS

Odds ratios (ORs) for prone and side sleeping compared with supine sleeping for the last sleep were 13.9 (95% confidence interval 8.2-24) and 3.5 (2.1-5.7). Infants 13 to 24 weeks old had particularly high risk in prone and side sleeping, at 28.5 (7.9-107) and 5.9 (1.6-22). OR for prone sleeping was higher in girls, at 30.4 (11-88), than in boys, 10.3 (5.5-19). We found strong combined effects of sleeping position and prenatal risk factors (more than multiplicative). The OR for prone and side sleeping was increased for infants with birth weight <2500 g, at 83 (25-276) and 36.6 (13-107); for preterm infants, at 48.8 (19-128) and 40.5 (14-115); and for intrauterine growth retarded, at 38.8 (14-108) and 9.6 (4.3-22), compared with supine position in infants without these prenatal factors. The combined effect of nonsupine positions and intrauterine growth retarded was highest among 13- to 24-week-old infants. Effects of combined presence of nonsupine sleeping positions and each of the factors of smoking in pregnancy, young maternal age, higher parity, low level of maternal education, and single motherhood were more than additive. Attributable fractions in the population for prone and side sleeping were 18.5% and 26.0%.

CONCLUSIONS

Both prone and side sleeping increased the risk of SIDS. The risk was increased further in low birth weight infants, preterm infants, and infants at the age of 13 to 24 weeks, suggesting that SIDS may be triggered by nonsupine sleeping in infants with prenatal risk factors during a vulnerable period of postnatal development.

Gender and the sudden infant death syndrome. New Zealand Cot Death Study Group

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.

Bedsharing promotes breastfeeding

OBJECTIVE

Because breastfeeding is thought to be protective against sudden infant death syndrome (SIDS), environmental or child care factors that promote breastfeeding might reduce infant vulnerability to SIDS. The effect of mother-infant bedsharing on nocturnal breastfeeding behavior was studied in 20 routinely bedsharing and 15 routinely solitary sleeping Latino mother-infant pairs when the infants were 3 to 4 months old.

METHODOLOGY

All pairs were healthy and exclusively breastfeeding at night. The videotape portion of all-night laboratory polysomnographic studies was used for the analyses. For each pair, an adaptation night was followed by one night each of bedsharing and solitary sleeping.

RESULTS

The most important finding is that when tested in their usual sleeping conditions, routinely bedsharing infants breastfed approximately three times longer during the night than infants who routinely slept separately: this reflected a two-fold increase in the number of breastfeeding episodes and 39% longer episodes. Breastfeeding was also facilitated on the bedsharing night relative to the solitary night within the routinely bedsharing group: the number and total duration of breastfeeding episodes were significantly larger on the bedsharing night.

CONCLUSIONS

We suggest that, by increasing breastfeeding, bedsharing might be protective against SIDS, at least in some contexts. Furthermore, maternal reproductive physiology could be impacted because nursing frequency affects ovulation. This is the first study to directly measure nocturnal breastfeeding behavior in any cultural group.

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

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 non-smoking 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.

SIDS, illness, and acute medical care. New Zealand Cot Death Study Group

One component of the Back to Sleep campaign to reduce the risk of sudden infant death syndrome (SIDS) is the recommendation that parents seek medical attention if their infant is unwell. The aim of this study was to investigate of SIDS could in part be explained by sick infants not getting appropriate medical care. Data on symptoms of illness and on acute medical contacts made for infants dying from SIDS (n = 390) within two weeks of their death were compared with those from a randomly selected group of control infants (n = 1592). SIDS cases had more severe illness than controls (odds ratio (OR) = 3.43; 95% confidence interval (CI) = 1.69 to 5.38), and were more likely to have seen a general practitioner (OR = 1.37; 95% CI = 1.09 to 1.73) or attended hospital (OR = 3.43, 95% CI = 1.09 to 1.73). Only 1.3% of all SIDS cases had symptoms suggesting severe illness and had not seen a general practitioner. A lack of medical contacts in the two weeks before death does not contribute to the risk of SIDS.

Pre- and postnatal medical care and risk of sudden infant death syndrome

The current study investigated whether sufficient attendance at prenatal and postnatal checks affects the risk of sudden infant death syndrome. A case-control study in the Tyrol enrolled 99 infants with sudden infant death syndrome that occurred between 1984 and 1994, and 136 randomly selected control cases. The risk of sudden infant death syndrome was higher in infants whose mothers attended less than five antenatal health checks than in the group with at least five or more visits (OR 5.1; p < 0.01). Babies who received medical help beyond routine health controls had a lower risk than those who did not (OR 0.32; p < 0.001). These differences persisted when social and demographic variables (mother's age at delivery, educational level, marital status, parity and gestational age) were taken into account. Our study identified inadequate antenatal and postnatal care as a risk indicator for sudden infant death syndrome and as a potential target for further educational work. Clinical recommendations should await the results of further evaluations.

V-shaped pillows and unsafe infant sleeping

OBJECTIVE

To investigate the possibility that adult size V-shaped pillows may be associated with accidental asphyxial deaths in infants.

METHODOLOGY

Review was undertaken of all cases of sudden infant death presenting to the Women's and Children's Hospital in Adelaide involving infants who had been found on adult size V-shaped pillows.

RESULTS

Four cases of sudden infant death were found in which infants were found sleeping on V-shaped pillows. All of the deaths had occurred in 1995. In two of the cases the pillows were considered to be implicated in the cause of death as the potential for obstruction of the infants' airways could be demonstrated on death scene reconstruction.

CONCLUSION

Adult size V-shaped pillows may be unsafe for use in small infants who may accidentally suffocate if trapped between the two arms, or under, the pillow. The use of such pillows to maintain the body position of sleeping infants should be discouraged.

A genetic basis for the sudden infant death syndrome sex ratio

Sudden infant death syndrome, in 36 global data sets comprising 67378 postneonatal autopsied cases, has a male fraction of 0.612 which is significantly greater than the male birth fraction of 0.5122. Each of the sex ratios in the 36 data sets cannot be rejected as a random sample from a P = 0.612 binomial distribution. We hypothesize that an X-linked two-allele (a,A) single gene may be responsible for this consistent behavior. The Hardy-Weinberg principle predicts, given a 5% excess male birth rate, that a recessive allele (a) associated with sudden infant death syndrome, having a frequency of q = 2/3, could be responsible for the male fraction of 0.612. The absence of the A allele would be a necessary precondition for sudden infant death syndrome. We hypothesize that the syndrome occurs only with additional rare environmental conditions and rare physiological factors leading to extreme hypoxic stress, which reduces the sudden infant death syndrome rate to the order of 1 per 1000 live births.

The use of breastmilk in a neonatal unit and its relationship to protein and energy intake and growth

OBJECTIVE

A nutritional audit was performed to determine whether current feeding regimes were achieving nutritional goals and to evaluate the use of breastmilk (BM) in a neonatal unit (NNU).

METHODS

All fluid consumed or infused daily was documented with daily weight and weekly length and head circumference measurements in 90 preterm infants (gestational age 30.1 +/- 2.6 weeks) while in the NNU for 60 +/- 27 days. Daily protein and energy intakes were calculated using values for South Australian preterm BM.

RESULTS

Parenteral nutrition provided 85% of the daily energy in week 1 falling to 11% by week 6. Ninety per cent of infants received some of their mother's BM and 62% were discharged at least partially breastfed. Protein and energy intakes were 1.03 +/- 0.35 g and 55 +/- 10 kcal/kg/day in week 1, increasing to 2.52 +/- 0.60 g and 109 +/- 15 kcal/kg per day by week 4. Protein intake correlated with weight gain (r2 = 0.39). Weight gain was 14.0 +/- 2.0 g/kg per day and z-scores for weight declined from -0.25 on admission to -1.22 on discharge, P < 0.0001. When infants were divided into two groups comprising those who received BM or formula as their predominant enteral feed, growth and protein intake (but not energy intake) were lower in the BM-fed infants. However, enteral feeds were tolerated earlier and more quickly in those infants receiving predominantly BM.

CONCLUSION

Energy requirements were readily met using current feeding regimes for preterm infants but protein intakes were marginal. Mothers of preterm infants had similar breastfeeding rates to mothers of term infants in South Australia. The long-term effects of the lower growth rates of preterm infants fed predominantly BM compared with those fed predominantly formula are unknown and need be balanced against the benefits of BM.

Can risk factors for over-heating explain epidemiological features of sudden infant death syndrome?

Sudden infant death syndrome is characterized by a number of epidemiological features that have defied simple explanation. Overheating is believed to play a role in its causation. Overheating can be caused by changes in heat production, changes in insulation of the infant, or changes in the external environmental temperature. Risk factors may influence any of these variables. A model is proposed which links risk factors for overheating to the epidemiological distribution of sudden infant death syndrome. This model might account for the frequently reported association between formula-feeding and sudden infant death syndrome.

Assessment of exposure misclassification bias in case-control studies using validation data

It has recently been shown that the bias due to misclassification of a binary exposure in case-control studies can be simply expressed in terms of so-called quality indices. Quality indices are measures of the degree of misclassification that are symmetric with respect to the true and measured exposure. They can be estimated from sub-study validation data and used to estimate the bias. Bias is not present if quality indices are nondifferential with respect to cases and controls. In this article the sampling distribution of these indices is investigated by developing formulae for their standard errors and these formulae are used to derive the standard error of the estimated bias. Simulation studies are used to confirm the validity of the formulae. The formulae are used to assess the bias in two studies of risk factors for Sudden Infant Death Syndrome (SIDS) and can be applied to the assessment of diagnostic tests.

Life events, social support and the risk of sudden infant death syndrome

The effects of a lack of maternal social support and stressful life events on the risk of Sudden Infant Death Syndrome (SIDS) were examined by case-control design: 390 cases and 1592 control infants. A seven item index of mother's social support was used. A possible 21 life events experienced by each family were summed and then put into one of three categories: 0-2, 3-5, and 6 or more life events. Similar levels of maternal social support were found for both groups. SIDS families experienced significantly more stressful life events than control families, but once social factors had been taken into account this association was lost.

Hyperthermia in sudden infant death

To determine whether preterminal hyperthermia is significantly associated with sudden infant death (SID), 140 structured interviews with parents of SID victims were compared with questionnaires filled in by a control group of parents living in the same area. All SID autopsies were performed between 1986 and 1992 at the Institute of Legal Medicine of Hannover Medical School according to the same protocol. Signs of profuse sweating (i.e. moist head, damp clothing or bedding) were present at the scene of death in 35.7% of cases. SID victims with signs of profuse sweating were more frequently found under their bedding (p < 0.001), were older (178 vs. 130 days) and the time period between when they were last seen alive and when they were found dead was longer (6.5 vs. 4.5 hours p < 0.01) compared to cases without sweating. Sweat on the head [odds ratio (OR) = 1.9; 95% confidence interval (CI) = 1.0, 3.6], and sweaty clothing and bedding (OR = 17.9; 95% CI = 8.7; 37.1) showed a significant association with the risk for SID. The pathophysiological basis for hyperthermia is SID remains to be determined. Hyperthermia could result from infection, overinsulation from excessive clothing with high environmental temperatures, covering of the infant's head or immature central thermoregulatory centres. The influence on the fatal outcome and the role in the pathogenesis of these deaths requires further research.

Higher rectal temperatures in co-sleeping infants

The effect on deep body temperature of infants co-sleeping (with either or both parents) is investigated in this case control study. Overnight continuous recordings of rectal temperature were made from 34 babies co-sleeping with one or both parents throughout the night and 34 infants matched for age, feeding regimen, parental smoking, thermal environment, sleeping position, and sex who slept alone. The co-sleeping infants had significantly higher rectal temperatures from two hours after bedtime, when the initial fall in sleeping body temperature was complete. The mean rectal temperature of co-sleeping infants between two and eight hours was 0.1 degree C higher than that of infants sleeping alone (p < 0.04). Given the very small variance in rectal temperature this probably reflects a considerable physiological difference between the two groups.

Symptoms, sweating and reactivity of infants who die of SIDS compared with community controls. New Zealand National Cot Death Study Group

OBJECTIVE

To describe the symptoms of illness reported by the parents of infants who have died of sudden infant death syndrome (SIDS) compared with those reported by community controls.

METHODOLOGY

A nationwide case-control study involving regions of New Zealand with 78% of all births between 1987 and 1990. Home interviews were completed with parents of 393 (81% of total) infants who died from SIDS in the post neonatal age group, and 1592 (88.4% of total) controls who were a representative sample of all hospital births in the study region.

RESULTS

Symptoms of infection were common in both cases and controls, but were not significantly different. Infants dying of SIDS, however, were likely to have symptoms suggestive of more severe illness in the 2 days before death (odds ratio [OR] = 3.02, 95% confidence interval [CI] 1.69-5.38). After adjusting for potential confounding this was still statistically significant (adjusted OR 2.36, 95% Cl 1.14-4.90). Also, babies dying of SIDS were more likely to have been less reactive to their environment in the 2 weeks before death compared with the controls (univariate OR 0.88, 95% Cl 0.55- 1.39, adjusted OR 0.55, 95% CI 0.29-0.88). 'Drenching' sweats at least weekly were reported for 15.6% of case infants compared with 5.9% of control infants (adjusted OR 2.12, 95% CI 1.53-3.39). Forty per cent of these infants had this symptom in the first 4 weeks of life when it was also associated with a significantly raised risk of SIDS. Apnoea lasting more than 20 s was reported for 13.2% of case infants compared with 5.3% of control infants (adjusted OR 1.93, 95% CI 1.17-3.17). Similarly, 71.8% of case infants' faces were reported to never turn red while awake compared to 49.8% of control infants (adjusted OR 2.98, 95% CI 2.19-4.07).

CONCLUSIONS

Only a small number (6.4%) of babies who die of SIDS have symptoms of serious illness in the 2 days before death. There is support for the hypothesis that there is a group of babies dying of SIDS who have subtle abnormalities in autonomic control or arousal ability.

Marital status and births after losing a baby from sudden infant death

To describe the change in marital status and subsequent live births of mothers who have lost a baby from sudden infant death (SID or cot death), a postal questionnaire was sent to European mothers who had been interviewed approximately 3.7 years (range 2.2-5.2 years) previously as part of a nationwide case-control study. Mothers of 105 (60.3%) cases and 828 (76.9%) controls replied. Changes in marital status between the time of interview and the time of the postal questionnaire did not differ between mothers of cases and that of controls when adjusted for marital status at the time of death/nominated date for controls. Cases were more likely to have further children than controls (P < 0.001) and had them sooner after the death than after the nominated date for control babies (P < 0.001). Case mothers were more likely than controls to have a second child after the death/nominated date, however the interval between the first and second child after the death/nominated date was the same as that for controls.

CONCLUSIONS

Although the death of an infant is a major stress on marital relationships, at approximately 3.7 years marital breakdown is no higher than in the control population. After the death of her baby the mother "replaces" the child by having more children than control mothers and having the first one earlier than control mothers. Mothers who lose a baby from SID are more fertile than the control population both before and after the death.

Smoking and the sudden infant death syndrome: results from 1993-5 case-control study for confidential inquiry into stillbirths and deaths in infancy. Confidential Enquiry into Stillbirths and Deaths Regional Coordinators and Researchers

OBJECTIVE

To investigate the effects of exposure to tobacco smoke and of parental consumption of alcohol and illegal drugs as risk factors for the sudden infant death syndrome after a national risk reduction campaign which included advice on prenatal and postnatal avoidance of tobacco smoke.

DESIGN

Two year population based case-control study. Parental interviews were conducted for each infant who died and four controls matched for age and date of interview.

SETTING

Three regions in England with a total population of 17 million people.

SUBJECTS

195 babies who died and 780 matched controls.

RESULTS

More index than control mothers (62.6% v 25.1%) smoked during pregnancy (multivariate odds ratio = 2.10; 95% confidence interval 1.24 to 3.54). Paternal smoking had an additional independent effect when other factors were controlled for (2.50; 1.48 to 4.22). The risk of death rose with increasing postnatal exposure to tobacco smoke, which had an additive effect among those also exposed to maternal smoking during pregnancy (2.93; 1.56 to 5.48). The population attributable risk was over 61%, which implies that the numbers of deaths from the syndrome could be reduced by almost two third if parents did not smoke. Alcohol use was higher among index than control mothers but was strongly correlated with smoking and on multivariate analysis was not found to have any additional independent effect. Illegal drug use was more common among the index parents, and paternal use of illegal drugs remained significant in the multivariate model (4.68; 1.56 to 14.05).

CONCLUSIONS

This study confirms the increased risk of the sudden infant death syndrome associated with maternal smoking during pregnancy and shows evidence that household exposure to tobacco smoke has an independent additive effect. Parental drug misuse has an additional small but significant effect.

An analysis of sudden infant death syndrome in aboriginal infants

The purpose of this case-control study was to identify antenatal and perinatal risk factors for sudden infant death syndrome (SIDS) in Aboriginal infants in Western Australia (WA). Cases were all Aboriginal infants born in WA from 1980 to 1990 inclusive and classified as dying from SIDS in WA. Controls consisted of a matched group and a random group both selected from liveborn Aboriginal infants born from 1980 to 1990. Multivariate modelling showed that SIDS in Aboriginal infants was strongly related to young maternal age (< 20 years, odds ratio (OR) = 2.89), high parity (parity > 3, OR = 4.40) and being small-for-gestational age (OR = 3.36) but was not associated with single marital status (OR = 0.95) or male sex (OR = 0.97). Although the study was based on routinely collected data, results do highlight some important groups for SIDS prevention. To gain further knowledge in terms of SIDS in Aboriginal infants, there is an urgent need to collect information concerning infant care practices in the Aboriginal community.

Immunisation and the sudden infant death syndrome. New Zealand Cot Death Study Group

AIMS

To examine the relation between immunisation and the risk of sudden infant death syndrome (SIDS).

METHODS

A large nationwide case-control study. Parental held records were used to measure immunisation status.

RESULTS

Infants were at increased risk of SIDS if they had not received the 6 week, 3 month, and 5 month immunisations. After controlling for potential confounding variables, including those which measured health care use and infant illness, the relative risk of SIDS for infants not being immunised at 6 weeks was 2.1 (95% confidence interval = 1.2, 3.5). Four percent of cases died within four days of immunisation and 7.6% of control infants had been immunised within four days of the nominated date. There was a reduced chance of SIDS in the four days immediately following immunisation (OR = 0.5; 95% CI = 0.2 to 0.9).

CONCLUSIONS

Immunisation does not increase the risk of SIDS and may even lower the risk.

Play position is influenced by knowledge of SIDS sleep position recommendations

OBJECTIVE

This study determined whether knowledge of sleeping in the prone position as a risk factor for sudden infant death syndrome (SIDS) influences caregivers' positioning of their infants for play and sleep.

METHODOLOGY

One hundred caregivers attending Adelaide metropolitan Child Adolescent and Family Health Services (CAFHS) were surveyed by self-administered questionnaire.

RESULTS

Ninety-three per cent of parents reported that their knowledge of SIDS influenced infant positioning for sleep and 84% reported they never put their infant in the prone position for sleep. Thirty-seven per cent reported that SIDS knowledge did influence play positioning and 26% reported never placing their infant prone for play. There was a significant association (P = 0.002) between the influence of SIDS knowledge on play positioning and avoidance of the prone position for play.

CONCLUSIONS

Community educators may need to clarify that prone positioning for play is not a risk factor for SIDS and that it is desirable for infants to spend supervised wakeful time in the prone position.

Factors affecting rectal temperature in infancy

The recordings of 1197 overnight rectal temperatures from infants of up to 24 weeks of age have been analysed with respect to 12 variables, including a number of risk factors for sudden infant death syndrome. Multivariable regression was used to identify if parental smoking, bottle feeding, sleeping position, and birth weight affect the overnight rectal temperature of infants. The rectal temperature, averaged over the period from three to five hours after the infants were put to bed, correlated well (R = 0.36) with the collected variables. An increase in the infant's age, birth weight, and the supine sleeping position all decreased the night time rectal temperatures. However, an increase in the night time room temperature, weight, and the combination of bottle feeding and parental smoking produced an increase in rectal temperature. The individual effects of bottle feeding and parental smoking were not significant. The results show that some of the major risk factors have the effect of raising the rectal temperature of sleeping infants.

Factors that influence the choice of infant feeding

To consider some of the many factors that influence the choice to initiate and continue breast-feeding.

CONCLUSION

There is increasing recognition of the nutritional value and related health outcomes of breast-fed infants. Further research is essential to appraise the medical and social determinants of infant feeding practices, particularly the early discontinutation of breast-feeding. Paediatricians are in an ideal position to foster, encourage and support such research and to accept a wider role in advocacy of the infant's right to obtain optimal nutrition.

Factors associated with the age of introduction of solids into the diet of New Zealand infants. New Zealand Cot Death Study Group

OBJECTIVE

To describe the current timing of the introduction of solids in infancy and the factors influencing the decision to introduce solids.

METHODOLOGY

Eighteen hundred infants were selected randomly as part of the New Zealand Cot Death Study. Of these, 88% of the parent/caregivers were interviewed when their infant was aged between 1 and 12 months. They were asked when solids were first introduced into the diet.

RESULTS

By 12 weeks of age more than 20% of infants had been given solids; by 16 weeks and by 6 months 50 and 90% of babies, respectively, had been given solids. Maternal smoking, low educational achievement and not being breast-fed exclusively to 4 weeks of age were factors which were strongly associated with the early introduction of solids.

CONCLUSION

Half of New Zealand infants are being started on solids earlier than is presently recommended. More education is needed to promote the later introduction of solid foods into the diet.

Antenatal and intrapartum factors associated with sudden infant death syndrome in the New Zealand Cot Death Study

OBJECTIVE

To describe the relationship between antenatal and intrapartum factors and sudden infant death syndrome (SIDS).

METHODOLOGY

The New Zealand Cot Death Study was a 3 year case-control study, with 485 infants who died from SIDS in the postneonatal period and 1800 randomly selected control infants. Data were obtained from obstetric records, parental interview and community nursing records.

RESULTS

This study confirms many of the antenatal and intrapartum risk factors for SIDS noted in studies from both the southern and northern hemispheres. After controlling for potential confounders, such as occupational group and marital status, significant inverse effects were noted for interpregnancy interval, birthweight and gestation. Other factors that retained a significantly increased risk of SIDS were: increasing parity, bacteriological evidence of urinary tract infection (UTI) (adjusted odds ratio 1.73, 95% CI 1.10-2.73); smoking antenatally (AdjOR 2.14, 95% CI 1.61-2.84); less than six antenatal checks attended (AdjOR 1.84, 95% CI 1.19-2.84); second stage of labour less than 16 min (AdjOR 2.06, 95% CI 1.35-3.14) and multiple birth (AdjOR 3.23, 95% CI 1.70-6.02). No interaction was observed between maternal haemoglobin and antenatal smoking. Interactions were tested for and not found between antenatal smoking and three antenatal risk factors (UTI, short second stage of labour and number of antenatal appointments). The only significant interaction between these three factors and three modifiable postnatal risk factors (prone sleeping, bed sharing and bottle feeding) was between bed sharing and fewer antenatal appointments. The risk of SIDS associated with bed sharing was greater among those whose mothers had fewer antenatal appointments.

CONCLUSIONS

Although many of the previously identified antenatal and intrapartum risk factors for SIDS are confirmed, the risks of SIDS associated with obstetric factors are in general considerably lower than the risks associated with the four modifiable postnatal risk factors.

Higher rates of SIDS persist in low income groups

OBJECTIVE

To examine how changes in the rates of sudden infant death syndrome (SIDS) have varied in different income groups during a 25 year period.

METHODOLOGY

Census data were obtained for five census periods (1971, 1976, 1981, 1986 and 1991) on the number of SIDS cases and inevitable deaths. Census area units (CAU) were ranked according to the average income earned by adults over the age of 15 years for each census year. The CAU were then divided into three equal income groups: low, middle and high.

RESULTS

The rates of SIDS differed significantly between the three income groups for the 1991 census period with the low income SIDS rate being 4.6/1000 births compared to 1.2/1000 live births for the higher income groups (Chi-squared = 18.3, P < 0.0001). There was no association between rates of inevitable deaths and income groups.

CONCLUSION

Currently, low income groups have three times the rate of SIDS compared to those in higher income groups. The reason for this is probably because the disadvantaged groups carry an overall higher burden of risk factors for SIDS. This must be kept in mind as further SIDS educational programmes are developed and implemented.