Are risk factors for sudden infant death syndrome different at night?

AIMS

To determine whether the risk factors for SIDS occurring at night were different from those occurring during the day.

METHODS

Large, nationwide case-control study, with data for 369 cases and 1558 controls in New Zealand.

RESULTS

Two thirds of SIDS deaths occurred at night (between 10 pm and 7 30 am). The odds ratio (95% CI) for prone sleep position was 3.86 (2.67 to 5.59) for deaths occurring at night and 7.25 (4.52 to 11.63) for deaths occurring during the day; the difference was significant. The odds ratio for maternal smoking for deaths occurring at night was 2.28 (1.52 to 3.42) and that for the day 1.27 (0.79 to 2.03); that for the mother being single was 2.69 (1.29 to 3.99) for a night time death and 1.25 (0.76 to 2.04) for a daytime death. Both interactions were significant. The interactions between time of death and bed sharing, not sleeping in a cot or bassinet, Maori ethnicity, late timing of antenatal care, binge drinking, cannabis use, and illness in the baby were also significant, or almost so. All were more strongly associated with SIDS occurring at night.

CONCLUSIONS

Prone sleep position was more strongly associated with SIDS occurring during the day, whereas night time deaths were more strongly associated with maternal smoking and measures of social deprivation.

Socioeconomic status and preterm birth: New Zealand trends, 1980 to 1999

BACKGROUND

While a number of countries have reported rising preterm birth rates over the past two decades, none has examined the effects of socioeconomic status on preterm birth at a national level.

AIM

To document the changing incidence of preterm birth in New Zealand over the past 20 years and to determine whether particular socioeconomic or ethnic subsections of the population have contributed disproportionately to the changes seen.

METHODS

Birth registration data routinely available from the New Zealand Health Information Service were analysed for the period 1980-99. Information for a total of 1 079 478 singleton live births was linked by Domicile Code to the New Zealand Deprivation Index, a small area index of deprivation.

RESULTS

Singleton preterm birth rates rose by 37.2% during the 20 year period, from 4.3% in 1980 to 5.9% in 1999. Rates increased by 71.9% among those living in the most affluent areas, but by only 3.5% among those living in the most deprived areas, resulting in the disappearance of a socioeconomic gradient in preterm birth that had existed during the early 1980s.

CONCLUSIONS

This study challenges traditional thinking on the associations between socioeconomic status and preterm birth. Further research is necessary if the changes that have occurred in New Zealand over the past 20 years are to be fully understood.

The epidemiology of placental infarction at term

The incidence and associations of placental infarction at term were investigated as part of a population based case-control study of small for gestational age (SGA) infants. 509 placentas from women delivering SGA infants (SGAP) and 529 placentas from women delivering infants with birthweights appropriate for gestational age (AGAP) were examined using fixed protocols for macroscopic identification and microscopic confirmation of infarction. Other information was obtained by maternal interview and from an obstetric database. Infarcts were found in 17.3 per cent of SGAP and 11.7 per cent of AGAP. This difference was in placentas with multiple infarcts not involving the placental margin and was significant in multivariate analysis (OR 1.66; 95 per cent CI 1.12,2.47). Multivariate analysis showed significant associations between the presence of any infarct and maternal hypertension in both SGAP (OR=4.00; 95 per cent CI 1.96,8.16) and AGAP (OR 2.99; 95 per cent CI 1.23,7.32); maternal smoking, associated with a lesser risk in SGAP only (OR=0.31; 95 per cent CI 0.13,0.73); maternal age at first pregnancy in a linear relationship with AGAP only (beta co-efficient 0.09, P=0.0034); and between some ethnic groups. We conclude that at least five factors have independent associations with the incidence of placental infarction and these associations differ by site and age of infarcts.

Nasal and intrapulmonary haemorrhage in sudden infant death syndrome

BACKGROUND

Fresh intrapulmonary and oronasal haemorrhages in cases of sudden infant death syndrome (SIDS) might be markers for accidental or intentional smothering inappropriately diagnosed as SIDS.

AIM

To compare the incidence, epidemiological association, and inter-relation of nasal haemorrhage, intrapulmonary haemorrhage, and intrathoracic petechiae in infant deaths certified as SIDS.

METHODS

In SIDS cases from a large nationwide case-control study, a wide range of variables were compared in cases with and without reported nasal haemorrhage and, in a subgroup of cases, in those with and without pathologically significant intrapulmonary haemorrhage.

RESULTS

Nasal haemorrhage was reported in 60 of 385 cases (15%) whose parents were interviewed. Pathologically significant intra-alveolar pulmonary haemorrhage was found in 47% of 115 cases studied, but was severe in only 7%. Infants with nasal haemorrhage had more haemorrhage into alveoli and air passages than age matched cases without nasal haemorrhage. In multivariate analysis, nasal haemorrhage was associated with younger infant age, bed sharing, and the infant being placed non-prone to sleep. Intrapulmonary haemorrhage was associated with the same three factors in univariate analysis, but in multivariate analysis only younger infant age remained statistically significant. There was no significant association between nasal or intra-alveolar haemorrhages and intrathoracic petechiae.

CONCLUSIONS

Nasal and intrapulmonary haemorrhages have common associations not shared with intrathoracic petechiae. Smothering is a possible common factor, although is unlikely to be the cause in most cases presenting as SIDS.

Risk factors for small-for-gestational-age babies: The Auckland Birthweight Collaborative Study

OBJECTIVE

This case-control study determined whether internationally recognized risk factors for small-for-gestational-age (SGA) term babies were applicable in New Zealand.

METHODOLOGY

All babies were born at 37 or more completed weeks of gestation in one of three hospitals in Auckland. Cases weighed less than the sex specific 10th percentile for gestational age at birth, and controls (appropriate-for-gestational-age (AGA)) were a random selection of heavier babies. Information was collected by maternal interview and from obstetric databases.

RESULTS

Information from 1714 completed interviews (844 SGA and 870 AGA) was available for analysis. Computerized obstetric records were available for 1691 of the 1701 women who consented to such access. In a multivariate analysis allowing for sex, gestational age at birth, social class and other potential confounders, mothers who smoked had a significantly increased risk of an SGA baby (adjusted OR 2.41; 95% CI 1.78-3.28), as did primiparous mothers (adjusted OR 1.34; 95% CI 1.03-1.73), mothers of Indian ethnicity (adjusted OR 3.22; 95% CI 1.95-5.30), women with pre-eclamptic toxaemia (adjusted OR 2.42; 95% CI 1.08-5.40) and those with pre-existing hypertension toxaemia (adjusted OR 5.49; 95% CI 1.81-16.71). Mothers of SGA infants were shorter (P < 0.001) and reported lower prepregnancy body weights (P < 0.001) than mothers of AGA infants. The population attributable fraction for smoking suggests that up to 18% of SGA infants born in the ABC Study could be related to maternal smoking.

CONCLUSIONS

Risk factors associated with SGA births in other countries are also important in New Zealand. Smoking in pregnancy is an important and potentially modifiable behaviour, and efforts to decrease the number of women who smoke during pregnancy should be encouraged.

Parental reported apnoea, admissions to hospital and sudden infant death syndrome

Three studies were undertaken: (i) a nation-wide case-control study for sudden infant death syndrome (SIDS), with 393 cases and 1592 controls, examined the association between parental reported apnoea and SIDS; (ii) a case-cohort study, with 84 cases of parental reported apnoea and 1502 controls, aimed to identify risk factors for apnoea; and (ii) national hospital admission data for ALTE and national SIDS mortality data were compared for the years 1986 to 1994. Parental reported apnoea was associated with a significant increased risk of SIDS [adjusted odds ratio (OR) 1.86; 95% confidence interval (CI) 1.12, 3.09]. The population attributable risk was 8%. There was a significant increased risk for parental reported apnoea in infants who did not die after adjustment for potential confounders with maternal smokers, short gestation and admission to the neonatal unit. There was no association with prone sleeping position, co-sleeping and bottle feeding. The mean annual admission rate for ALTE was 9.4/1000 live births. This did not change significantly over the study period (1986-1994). In contrast, the SIDS mortality rate decreased from over 4/1000 to 2.1/1000. Admission rates were higher for Maori infants and boys.

CONCLUSION

It may be concluded that the relationship between parental reported apnoea and SIDS is tenuous.

The burden of symptoms of asthma, allergic rhinoconjunctivitis and atopic eczema in children and adolescents in six New Zealand centres: ISAAC Phase One

AIM

To describe the burden of symptoms of asthma, allergic rhinoconjunctivitis and atopic eczema in children in six New Zealand centres.

METHODS

The International Study of Asthma and Allergies in Childhood (ISAAC) Phase One was undertaken in Auckland, Bay of Plenty, Hawke's Bay, Wellington, Nelson and Christchurch during 1992-1993. In each centre, approximately 3,000 six to seven year old children and 3,000 thirteen to fourteen year old adolescents were studied, a total of 37,592 participants. Both age groups answered written questionnaires and the adolescents a video questionnaire about asthma symptoms.

RESULTS

The prevalences of symptoms were high, for asthma 25% and 30%, allergic rhinoconjunctivitis 10% and 19%, and atopic eczema 15% and 13% in each age group respectively. More than 40% of participants had symptoms in the last year of at least one condition, most commonly asthma. There were no significant differences among regions, except for six to seven year olds in Nelson who had significantly lower prevalences of some symptoms of asthma and allergic rhinoconjunctivitis.

CONCLUSIONS

Asthma and allergies are common in New Zealand, with resultant morbidity and cost. However, there is little regional variation with the exception of lower rates in Nelson children. Explanations for these findings will be the subject of further studies.

The relationship of per capita gross national product to the prevalence of symptoms of asthma and other atopic diseases in children (ISAAC)

BACKGROUND

Increasing prevalence and worldwide variation in asthma and other atopic diseases suggest the influence of environmental factors, at least one possibly related to socioeconomic wellbeing. This paper examines the relationship of symptoms of asthma, rhinitis and eczema with gross national product per capita (GNP per capita).

METHODS

The prevalences of atopic symptoms in 6-7- and 13-14-year-old children were assessed in 91 centres (from 38 countries) and 155 centres (from 56 countries), respectively, in the International Study of Asthma and Allergy in Childhood (ISAAC). These symptoms were related to 1993 GNP per capita for each country as reported by the World Bank. The relationships between symptoms of atopic diseases and infant mortality, the human development index and 1982 GNP per capita were also considered.

RESULTS

The countries in the lowest quartile of GNP per capita have the lowest median positive responses to all the questions on symptoms of asthma, rhinitis and eczema. There was a statistically significant positive association between wheeze in the last 12 months and GNP per capita in the 13-14-year age group, but not in the 6-7-year age group. There was also a positive association between GNP per capita and eczema in both age groups.

CONCLUSIONS

The positive associations between GNP per capita and atopic symptoms being of only moderate strength suggests that the environmental factors are not just related to the wealth of the country.

The impact of pacifier use on breastfeeding: a prospective cohort study

OBJECTIVES

To determine the predictors of pacifier use during the first year of life and to assess the influence of pacifier use on the duration of breastfeeding.

METHODOLOGY

A prospective cohort study was conducted. Three hundred and fifty mother-infant pairs were followed to 1 year of age to determine the impact of the use of a pacifier on the duration of breastfeeding.

RESULTS

A cohort of 441 mothers were enrolled and 79% participated. Ninety four per cent were followed up to 1 year. Daily pacifier use was associated with early cessation of breastfeeding (risk ratio (RR) 1.71; 95% confidence interval (95%CI) 1.29, 2.28) and a reduced duration of full breastfeeding (adjusted (adj.) RR 1.35; 95%CI 1.05, 1.74). Finger sucking was not associated with a reduced duration of breastfeeding (RR 1.05; 95%CI 0.81, 1.37). Pacifier use less than daily was not associated with a change in duration of breastfeeding (RR 1.02; 95%CI 0.75, 1.39). Most mothers commenced the use of a pacifier within the first month. Multiple logistic regression analysis found that the use of a pacifier was associated with male gender (adj. RR 1.97; 95%CI 1.23, 3.13), maternal smoking in pregnancy (adj. RR 2.23; 95%CI 1.01, 4.95), and low maternal confidence with breastfeeding (adj. RR 2.70; 95%CI 1.48, 4.93).

CONCLUSIONS

Daily pacifier use is associated with a reduced duration of breastfeeding. Less frequent pacifier use does not reduce the duration of breastfeeding.

Maternal cannabis use in the sudden death syndrome

The smoking of cannabis and tobacco is common in many countries. In contrast to tobacco, which is an established risk factor for the sudden infant death syndrome (SIDS), nothing is known about cannabis and its effects on SIDS risk. We analysed data collected in a nation-wide case control study in New Zealand (393 cases, 1592 controls) to determine if there is any association between maternal cannabis use and SIDS risk. Adjusting for ethnicity and maternal tobacco use, the SIDS odds ratio for >weekly maternal cannabis use since the infant's birth was 2.23 (95% CI = 1.39, 3.57) compared to non-users; and the multivariate odds ratio was 1.55 (95% CI = 0.87, 2.75). We conclude that frequent maternal cannabis use may be a weak risk factor for SIDS, but this finding requires further research.

GDNF and GFRalpha-1 are components of the axolotl pronephric duct guidance system

In mammals, secretion of GDNF by the metanephrogenic mesenchyme is essential for branching morphogenesis of the ureteric bud and, thus, metanephric development. However, the expression pattern of GDNF and its receptor complex-the GPI-linked ligand-binding protein, GFRalpha-1, and the Ret tyrosine kinase signaling protein-indicates that it could operate at early steps in kidney development as well. Furthermore, the developing nephric systems of fish and amphibian embryos express components of the GDNF signaling system even though they do not make a metanephros. We provide evidence that GDNF signaling through GFRalpha-1 is sufficient to direct pathfinding of migrating pronephric duct cells in axolotl embryos by: (1) demonstrating that application of soluble GFRalpha-1 to an embryo lacking all GPI-linked proteins rescues PND migration in a dose-dependent fashion, (2) showing that application of excess soluble GFRalpha-1 to a normal embryo inhibits migration and that inhibition is dependent upon GDNF-binding activity, and (3) showing that the PND will migrate toward a GDNF-soaked bead in vivo, but will fail to migrate when GDNF is applied uniformly to the flank. These data suggest that PND pathfinding is accomplished by migration up a gradient of GDNF.

CLINICAL REVIEW ARTICLE: Is changing the sleep environment enough? Current recommendations for SIDS

Sudden infant death syndrome (SIDS or cot death) was the major cause of post-neonatal infant death in many countries in the late 1970s and 1980s. There is now very strong evidence that public intervention campaigns targeting the prone sleeping position, which had been identified by epidemiological studies as a major risk factor, were followed by substantial falls in the rate of SIDS. In the present review we discuss the evidence on which current recommendations for the prevention of SIDS are based. The prone sleeping position is now clearly causally associated with SIDS. Further reductions in SIDS may be produced by recommending the back sleeping position as opposed to the side position. Maternal smoking in pregnancy and bed sharing by infants of mothers who smoke are also strongly associated with SIDS, but have been harder to influence. Paternal smoking has also been implicated, although the magnitude of the reported risk is small. Finally, breastfeeding, pacifier use and having the infant sharing the parents bedroom, but not the bed, may also reduce risk. Continued reductions in SIDS mortality will require innovative public health education to target these major risk factors, while building on the "back to sleep" approach.

Plastic wrapping of cot mattresses: results from a pilot study

AIM

To assess the prevalence of plastic wrapping of cot mattresses and their thickness.

METHODS

Mothers of infants less than six months attending Plunket clinics in Central Auckland were interviewed. The thickness of the plastic was measured.

RESULTS

99 of 110 (90%) mothers invited to participate were visited at home. The sample was socioeconomically advantaged. Most infants were breastfed and few slept prone. The prevalence of plastic wrapped cot mattresses was 23.2%, of which sixteen (out of 23) used BabeSafe and seven used other types. The mean thickness of the BabeSafe was 0.15 mm (range 0.12-0.19 mm) and the other types were 0.10 mm (range 0.04-0.13 mm). One sample of plastic was 0.04 mm.

CONCLUSION

Thin plastic wrapping is being used and is potentially dangerous.

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.

Horizontal Distribution Patterns of Testate Amoebae (Protozoa) in a Sphagnum magellanicum Carpet

The distribution of soil microorganisms is generally believed to be patchy and to reflect habitat heterogeneity. Despite this general rule, the amount of existing data on species distribution patterns is scarce. Testate amoebae (Protozoa; Rhizopoda) are an important component of soil microbial communities and are increasingly used in ecological and paleoecological studies of Sphagnum-dominated peatlands, but data on the spatial structure of communities are completely lacking. This is an important aspect since quantitative models used for paleoecological reconstruction and monitoring are based on species assemblages. We explored the distribution patterns of testate amoebae distribution in a macroscopically homogeneous Sphagnum carpet, down to a scale of several centimeters. Distributions maps of the species and spatially constrained sample groups were produced. Multivariate and individual spatial autocorrelations were calculated. The importance of spatial structure was quantified by canonical correspondence analysis. Our ultimate goal is to find the finest resolution of environmental monitoring using testate amoebae. The distribution patterns differed among species, resulting in a complex spatial structure of the species assemblage in a whole. Spatial structure accounted for 36% of the total variation of species abundance in a canonical correspondence analysis constrained by spatial variables. This structure was partly correlated to altitude (microtopography) at a very fine scale. These results confirmed the existence of significant broad- and fine-scale spatial structures within testate amoebae communities that could in part be interpreted as effects of ecological gradients. This shows that, on a surface area of 0.25 m(2), ecological conditions which look uniform from a macroscopic point of view are not perceived as such by Sphagnum-inhabiting organisms. Therefore, testate amoebae could prove very useful to monitor fine-scale ecological processes or disturbances. Studies of the species' spatial distribution patterns in combination with autoecological studies are needed and should be included in the toolbox of biomonitoring itself.

Previous breastfeeding does not alter thymic size in infants dying of sudden infant death syndrome

The relationship between thymic weights and previous feeding histories was examined in 294 infants of 37 wk gestation or more dying of sudden infant death syndrome (SIDS). One hundred and sixty-five infants had been breastfed exclusively, 89 had been partially breastfed and 40 had never been breastfed. We found no relationship between thymic weight and type of previous feeding. The difference between these findings in SIDS and the substantially greater thymic size previously reported in 4-mo-old breastfed living infants deserves further study.

Factors associated with the duration of breastfeeding

A cohort study of healthy term infants was conducted to identify factors associated with breastfeeding duration. Three hundred and fifty mothers delivering in one obstetric hospital in Auckland, New Zealand were recruited. Ninety-five percent were followed up until 1 y. Breastfeeding was initiated by 97.4%, the median duration of breastfeeding was 7.6 mo, and 30% were continuing some breastfeeding at 12 mo. Adjusted risk ratios for shorter duration of breastfeeding were: maternal age <25 y, 2.33 (95% confidence interval = 1.33, 4.05); maternal age 25-34, 1.45 (1.01, 2.09) compared to maternal age > or =35; planning to cease breastfeeding < or =6 mo, 2.39 (1.65, 3.46); planning to breastfeed for as long as possible, 1.48 (1.00, 2.18), or not knowing plans 2.13 (1.36, 3.32) when compared to planning to cease breastfeeding after 6 mo; inverted nipples, 2.02 (1.26, 3.23), daily dummy use 1.62 (1.20, 2.18) or use of formula in the first month 2.79 (2.05, 3.80). Reporting mastitis, 0.67 (0.48, 0.94), and sharing the mother's bedroom at 3 mo, 0.69 (0.51, 0.92) were associated with a reduced risk for shorter duration of breastfeeding. We recommend that during the antenatal period attention be directed at mothers' plans for duration of breastfeeding, that mothers be encouraged to have their baby in their bedroom, and that the use of formula and dummies should be discouraged in the first months of life.

Mastitis in the first year postpartum

BACKGROUND

Limited information is available about the frequency and risk factors for lactation mastitis. The purpose of this study was to investigate frequency, risk factors, and outcome for lactation mastitis.

METHODS

We analyzed data from a cohort study of 350 mothers with healthy term infants, who were followed up for one year postpartum.

RESULTS

Eighty-three women (23.7% of the sample) reported one or more episodes of mastitis symptoms, and 61 (17.4%) women reported symptoms including fever. Fifty-six women (16%) received one or more courses of antibiotics for mastitis. Thirty women (8.5%) of the total cohort had recurrent episodes of mastitis symptoms. A total of 123 episodes of mastitis symptoms were reported. No cases of abscess were reported. Using multiple logistic regression, the adjusted risk ratio for mastitis symptoms associated with sore nipples in the first month was 2.07 (95% CI = 1.17, 3.66). A reduced risk of mastitis was associated with maternal smoking during pregnancy, with supplementation with water in the first month, and with the use of a pacifier on a daily basis within the first month. A history of mastitis symptoms was associated with a longer overall duration of breastfeeding.

CONCLUSIONS

Our results suggest that mastitis may be a marker for an ample milk supply. Mothers presenting with mastitis can be reassured that the outlook for continued successful lactation is good. Further research is needed to investigate the reasons for recurrence of mastitis and the etiology of episodes occurring late in lactation.

Changing infants' sleep position increases risk of sudden infant death syndrome. New Zealand Cot Death Study

OBJECTIVE

To examine whether the prone sleeping position may increase the risk for sudden infant death syndrome (SIDS), particularly in infants unused to prone sleep.

DESIGN

A 3-year (1987-1990) case-control study.

SETTING

Nationwide study in New Zealand.

SUBJECTS

Four hundred eighty-five infants who died of SIDS and 1800 controls.

MAIN OUTCOME MEASURES

Infants were classified as unaccustomed to prone if their usual sleep position was nonprone and they were placed prone for the last sleep. Secondary prone was used to describe infants placed nonprone but found prone.

RESULTS

Infants usually and last placed nonprone were at the lowest risk for SIDS (odds ratio [OR], 1.0); those usually and last placed prone were at increased risk (adjusted OR, 4.6; 95% confidence interval, 3.4-6.3). Risk was greatly increased among infants unaccustomed to the prone position (adjusted OR, 19.3; 95% confidence interval, 8.2-44.8). These infants accounted for 8% (31/ 386) of all SIDS deaths. Ninety percent (28/ 31) of infants in this group were found prone, and 71% (20/28) of those found prone were found with their faces turned down into bedding-a position in which asphyxia has been implicated as a mechanism of death. In addition, 138 infants who died of SIDS were last placed nonprone. Forty-seven infants (34%) in this group were found prone (secondary prone), and 60% (28/47) of those found prone were found with their faces turned down into the bedding. This group accounted for 12% of all SIDS deaths. Most of these infants (91% [43/47]) were usually placed nonprone.

CONCLUSIONS

Infants placed supine to sleep were at the lowest risk of SIDS, which supports the recommendation that this is the preferred sleeping position for healthy infants. In New Zealand, 20% of SIDS deaths involved lack of experience with the prone sleeping position. Our findings suggest the possibility that an infant's competence in escaping from potentially lethal situations during prone sleep (eg, the face-down position) may be impaired by inexperience in prone sleeping. Great caution should be exercised in placing infants unaccustomed to the prone sleeping position in the prone position.

Water fluoridation and the sudden infant death syndrome

AIMS

To determine whether exposure to fluoridated water supplies prenatally or postnatally at the time of death increases the risk of sudden infant death syndrome (SIDS).

METHODS

A nationwide, case-control study, with infant's water fluoridation status determined from census area unit information for mother's usual address at the time of the infant's birth, infant's usual address at the time of death / nominated sleep and address where infant died / was at nominated sleep. SIDS risk associated with fluoride exposure postnatally was assessed according to method of infant feeding (breast or reconstituted formula), for the two days prior to infant's death / nominated sleep.

RESULTS

Infants exposed to fluoridated water supplies during pregnancy were not at increased risk for SIDS, adjusted odds ratio (OR) 1.19 (95% confidence interval (CI) 0.82, 1.74). For breast-fed infants at the time of death / nominated sleep, fluoridated water exposure was not associated with an increased risk for SIDS, adjusted OR 1.09 (95% CI 0.66, 1.79). Similarly, 'fluoridated' formula feeding, when compared with 'unfluoridated' formula feeding, showed no increased risk of SIDS, adjusted OR 1.25 (95% CI 0.73, 2.13). There was no evidence of an interaction between fluoridation and infant feeding for the last two days (chi2 = 0.171, df = 1, p = 0.68).

CONCLUSION

Exposure to a fluoridated water supply prenatally or postnatally at the time of death did not affect the relative risk for SIDS.

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.

Seasonal differences in risk factors for sudden infant death syndrome. The New Zealand Cot Death Study Group

The aim of this study was to explore whether the risk of sudden infant death syndrome (SIDS) associated with prone sleeping position and other risk factors varies with season. The study was a large nation-wide case-control study, which compared 485 cases with 1800 controls. Parents of 393 (81.0%) cases and 1591 (88.4%) controls were interviewed. Obstetric records were also examined. Infants dying in winter were older and had lower birthweights than those dying in summer. The increased risk of SIDS associated with prone sleeping position was greater in winter than in summer. In contrast, the increased risk of SIDS associated with excess thermal insulation and bed sharing was less in winter than in summer. Prone sleeping position accounts for about half of the difference between the mortality rate in summer and that in winter. This suggests that some factor related to season modifies the effect of prone sleeping position.

Resistance to Friend leukemia virus in transgenic mice expressing the native Fv-4 gene

Fv-4 is a truncated ecotropic retrovirus gene that codes for an envelope protein under control of a cellular promoter. It confers resistance to ecotropic murine leukemia viruses. Transgenic mice were derived using the native Fv-4 gene as the construct for microinjection. Two founder mice were derived. In both founder lines, there was no detectable expression of the transgene or resistance to Friend murine leukemia virus (FrMLV) in hemizygotes. In one line, the resistance was observed in homozygotes with Fv-4 RNA formation in the thymus but not in the spleen or in other tissues. In the other founder line, a homozygous male was identified. Double integrants, derived from breeding this homozygous male to homozygous females from the other founder line, were also resistant. These results indicate that the native gene confers the resistance in homozygous transgenic mice or double integrants derived from different founders but not hemizygotes.

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.

Homing of mononuclear cells from iliac lymph nodes to the genital and rectal mucosa in non-human primates

The route of immunization may affect the type of immunity that is induced. The objectives of this investigation were to establish in the non-human primate if the internal iliac lymph nodes (LN) function as an inductive site of immunity from which mononuclear cells home to the rectal and cervico-vaginal mucosa. Rhesus macaques were immunized with simian immunodeficiency virus (SIV) core antigen p27 in the proximity of the iliac lymph nodes, and compared with the intramuscular (i.m.) (deltoid or gluteal), and axillary LN routes of immunization. The macaques were then challenged rectally or vaginally by a particulate SIVp27 antigen which was applied to the mucosal surface. The tracking dye PKH26 was injected near the immunizing LN or i.m. site and a week later the mucosal and lymphoid tissues were examined at autopsy. Preferential homing of PKH26-labeled cells from the internal iliac LN to the rectal and vaginal mucosa was demonstrated by flow cytometry after targeted iliac LN (TILN) but not after intramuscular (deltoid) or axillary LN immunization. Homing of the subsets of cells revealed that labeled CD4, CD8 and B cells, as well as monocytes were found in the rectum, colon, vagina or cervix. The results of this investigation shows that the route of immunization may affect regional mucosal immunity. Furthermore, the internal iliac LN may function as an inductive immunological site from which CD4, CD8 and B cells may home preferentially to the rectal, cervical and vaginal mucosa, as well as to the related regional but not the unrelated distal LN.

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.

Antibody-secreting cells specific for simian immunodeficiency virus antigens in lymphoid and mucosal tissues of immunized macaques

OBJECTIVES

To examine whether the route of immunization affects the induction of antibody-secreting cells (ASC) in the circulation of macaques. The distribution of ASC in the rectal mucosa and lymphoid tissues following challenge with simian immunodeficiency virus (SIV) was investigated.

DESIGN

Macaques were immunized with recombinant SIV gp120 and p27 antigens by the targeted iliac lymph node (TILN) route of immunization or the nasal and rectal route, augmented by intramuscular immunization [naso-rectal intramuscular (NRI)]. The macaques were challenged with live SIV by the rectal route and ASC were assayed in the circulation before and after SIV challenge, and in the tissues removed at post-mortem.

METHODS

ASC were examined in the circulation by Elispot assay. Mononuclear cells were prepared from peripheral blood, iliac and axillary lymph nodes and spleen. Rectal tissue was treated by enzyme digestion to elute mononuclear cells.

RESULTS

TILN and NRI immunization induced circulating IgA and IgG ASC to both gp120 and p27. Following rectal challenge with SIV, TILN macaques were protected from infection whereas NRI route-immunized and unimmunized controls became infected. IgA ASC to p27 were increased significantly in the iliac lymph nodes of the TILN immunized macaques compared with unimmunized controls (P < 0.05). Only IgA ASC were found in the rectal mucosa of the immunized protected macaques but both IgA and IgG ASC were detected in the unimmunized infected macaques. Overall the number of IgG ASC specific for p27 was significantly higher in the infected NRI and control macaques than in the protected macaques (P < 0.02). A progressive increase in IgG but not IgA ASC was detected in the peripheral blood mononuclear cells of the unimmunized infected macaques.

CONCLUSIONS

The results suggest that cells secreting IgA antibodies to p27 in the iliac lymph nodes of the TILN immunized macaques correlate significantly with protection from infection. The unimmunized infected macaques showed a progressive increase in IgG ASC in the peripheral blood after SIV challenge; this was found in the iliac and axillary lymph nodes and also in the spleen, suggesting that it is an immune response to the SIV infection.

The establishment and duration of breastfeeding. Part 2: Community influences

Most New Zealand mothers initiate breastfeeding in hospital, but many continue for only a relatively short time. This paper reports on mothers' and health care workers' perceptions of important community factors influencing the duration of breastfeeding. Data collection was by focus group discussions. The results indicate that some mothers have specific plans regarding the duration of breastfeeding but many do not. The importance of practical help, realistic role expectations, community acceptance especially amongst men, adequate maternity leave, and help for those returning to work is emphasised. Conflicting opinions exist about the difficulties of introducing older infants to bottles.

The establishment and duration of breastfeeding. Part 1: Hospital influences

Most New Zealand mothers initiate breastfeeding in hospital, but many continue for only a relatively short time. Focus group discussions with mothers and health care workers on their perceptions of important factors influencing the duration of breastfeeding indicated many negative initial hospital experiences. Specific concerns included overworked staff; lack of health care workers' skills, particularly in helping infants to latch on; inconsistent advice; noise and embarrassment in four bedded rooms; and the impact of changes in the provision of maternity services and funding.

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.

Risk factors for preterm birth: a New Zealand study

AIM

To identify risk factors for preterm birth.

METHODS

A cross sectional study. The study population was 1800 infants selected randomly from all babies born over a three-year period. Of these, 85 (4.8%) were classified preterm (less than 37 completed weeks gestation). Data were collected from obstetric records and parental interviews.

RESULTS

Risk factors associated with an increased risk of preterm birth after controlling for potential confounders included smoking during pregnancy (adjusted relative risk (RR) = 2.7, 95% confidence interval (CI) = 1.3, 5.4), and multiple birth (adjusted RR = 48.8, 95% CI = 18.1, 131.4). Urinary tract infection was significant at the 7% level (adjusted RR = 2.3, 95% CI = 1.0, 5.6). Alcohol intake in third trimester was associated with a reduced risk of preterm birth (adjusted RR = 0.4, 95% CI = 0.2, 0.7).

CONCLUSION

Maternal smoking and multiple births were the most important modifiable risk factors in this study for preterm birth and may contribute to 17% and 11% of preterm births respectively.

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.

Why is sudden infant death syndrome more common at weekends? The New Zealand National Cot Death Study Group

OBJECTIVES

To determine whether the prevalence of known risk factors and the magnitude of their association with sudden infant death syndrome (SIDS) differed between weekends and weekdays.

METHOD

A large nationwide case-control study, comparing interview data for 393 cases with 1591 controls.

RESULTS

Sudden infant death syndrome occurred more often at weekends, more deaths occurring on Sunday than on any other day of the week. Significant interaction effects were found between weekends and sharing a room with an adult and the parents going to a party. After adjustment for confounders, room sharing was less protective at the weekends (odds ratio (OR) = 0.66, 95% confidence interval (CI) 0.43 to 1.03) than it was on weekdays (OR = 0.41, 95% CI 0.30 to 0.57) using not room sharing and weekdays as the reference group. Although the likelihood of SIDS after a party was higher at weekends (OR = 2.47, 95% CI 1.11 to 5.47) than on weekdays (OR = 0.55, 95% CI 0.21 to 1.37), few cases were reported. Being Maori (OR = 3.35, 95% CI 1.75 to 6.43) or the child of an unmarried mother (OR = 3.91, 95% CI 2.20 to 6.92) were risk factors for SIDS occurring on Sundays.

CONCLUSIONS

The increase in SIDS at weekends may be explained in part by the lesser protective effect of sharing a bedroom with an adult at that time. It may also be related to social activities that occur at weekends.

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.

Attitudes to the use of dummies in New Zealand; a qualitative study

AIMS

To explore experiences with, and attitudes to, the use of dummies (pacifiers).

METHODS

Seven focus group discussions were held with groups of mothers and of health professionals.

RESULTS

Most mothers and health care workers had a generally negative view of dummy use. This related particularly to dislike of toddlers with them and practical issues such as getting lost or dirty. All would allow their use in a very unsettled baby. No mothers had personally experienced problems with breastfeeding due to the use of a dummy, but concern about this possibility was expressed by some health care workers. Recommendations varied about the length of time that dummies need to be avoided.

CONCLUSIONS

Mothers in New Zealand use dummies selectively for their infants and were concerned with issues of weaning the baby from the dummy, keeping it clean and not losing it. In analysing the relationships between dummy use and breastfeeding it is important to take into consideration the context of dummy use.

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.

Housing and sudden infant death syndrome. The New Zealand Cot Death Study Group

AIMS

This paper examined factors relating to the infants' place of domicile to see whether they increased the risk of sudden infant death syndrome (SIDS) beyond social and environmental effects previously published.

METHODS

A case control study was undertaken in New Zealand between the years 1987-90. From all sudden infant death syndrome diagnoses over this time, parents of 393 (81%) sudden infant death syndrome infants consented to participate and these derive the cases. Controls were ascertained by randomly sampling 1800 infants from all babies born over 78% of the country. Parents of 1592 (88%) control infants consented to participate in the study.

RESULTS

The relative risk of sudden infant death for infants usually residing in houses rented from the government (State houses) was 1.73 (95% CI: 1.13, 2.66) times that of infants with parents owning their house, after adjusting for likely social, economic and environmental confounding factors. However, the type of housing, construction of housing, heating and age of housing was not associated with sudden infant death syndrome. Although house size, measured in terms of bedroom numbers, was similar for sudden infant death syndrome and control infants (chi 2 = 0.40, df = 2, p = 0.82), the number of people normally residing within these houses was different. Sudden infant death syndrome infants' houses were less likely to have two adults and more likely to have more children normally resident. Density calculations (derived by calculating the children and/or adult numbers divided by bedroom numbers) revealed a non significant increase in relative risk, suggesting that housing overcrowding was not associated with sudden infant death syndrome in New Zealand.

CONCLUSIONS

Infants domiciled in State houses are more likely to experience sudden infant death syndrome. However, this increased relative risk for sudden infant death syndrome appears to have little to do with the house per se and, perhaps, more to do with socioeconomic characteristics.

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.