Pj Berry

Interaction between bedding and sleeping position in the sudden infant death syndrome: a population based case-control study.

OBJECTIVE--To determine the relation between sleeping position and quantity of bedding and the risk of sudden unexpected infant death. DESIGN--A study of all infants dying suddenly and unexpectedly and of two controls matched for age and date with each index case. The parents of control infants were interviewed within 72 hours of the index infants death. Information was collected on bedding, sleeping position, heating, and recent signs of illness for index and control infants. SETTING--A defined geographical area comprising most of the county of Avon and part of Somerset. SUBJECTS--72 Infants who had died suddenly and unexpectedly (of whom 67 had died from the sudden infant death syndrome) and 144 control infants. RESULTS--Compared with the control infants the infants who had died from the sudden infant death syndrome were more likely to have been sleeping prone (relative risk 8.8; 95% confidence interval 7.0 to 11.0; p less than 0.001), to have been more heavily wrapped (relative risk 1.14 per tog above 8 tog; 1.03 to 1.28; p less than 0.05), and to have had the heating on all night (relative risk 2.7; 1.4 to 5.2; p less than 0.01). These differences were less pronounced in the younger infants (less than 70 days) than the older ones. The risk of sudden unexpected death among infants older than 70 days, nursed prone, and with clothing and bedding of total thermal resistance greater than 10 tog was increased by factors of 15.1 (2.6 to 89.6) and 25.2 (3.7 to 169.0) respectively compared with the risk in infants of the same age nursed supine or on their side and under less than 6 tog of bedding. CONCLUSIONS--Overheating and the prone position are independently associated with an increased risk of sudden unexpected infant death, particularly in infants aged more than 70 days. Educating parents about appropriate thermal care and sleeping position of infants may help to reduce the incidence of the sudden infant death syndrome.

Epidemiology of SIDS and Explained Sudden Infant Deaths

Objectives. To establish whether epidemiologic characteristics for sudden infant death syndrome (SIDS) have changed since the decrease in death rate after the “Back to Sleep” campaign in 1991, and to compare these characteristics with sudden and unexpected deaths in infancy (SUDI) from explained causes. Design. Three-year, population-based, case-control study. Parental interviews were conducted soon after the death and for 4 controls matched for age and date of interview. All sudden unexpected deaths were included in the study and the cause of death was established by a multidisciplinary panel of the relevant health care professionals taking into account past medical and social history of the mother and infant, the circumstances of death, and a full pediatric postmortem examination. Contributory factors and the final classification of death were made using the Avon clinicopathologic system. Setting. Five regions in England, with a total population of >17 million people, took part in the study. The number of live births within these regions during the particular time each region was involved in the study was 473 000. Study Participants. Three hundred twenty-five SIDS infants (91.3% of those available), 72 explained SUDI infants (86.7% of those available), and 1588 matched control infants (100% of total for cases included). Results. Many of the epidemiologic features that characterize SIDS infants and families have remained the same, despite the recent decrease in SIDS incidence in the United Kingdom. These include the same characteristic age distribution, few deaths in the first few weeks of life or after 6 months, with a peak between 4 and 16 weeks, a higher incidence in males, lower birth weight, shorter gestation, and more neonatal problems at delivery. As in previous studies there was a strong correlation with young maternal age and higher parity and the risk increased for infants of single mothers and for multiple births. A small but significant proportion of index mothers had also experienced a previous stillbirth or infant death. The majority of the SIDS deaths (83%) occurred during the night sleep and there was no particular day of the week on which a significantly higher proportion of deaths occurred. Major epidemiologic features to change since the decrease in SIDS rate include a reduction in the previous high winter peaks of death and a shift of SIDS families to the more deprived social grouping. Just more than one quarter of the SIDS deaths (27%) occurred in the 3 winter months (December through February) in the 3 years of this study. In half of the SIDS families (49%), the lone parent or both parents were unemployed compared with less than a fifth of control families (18%). This difference was not explained by an excess of single mothers in the index group. Many of the significant factors relating to the SIDS infants and families that distinguish them from the normal population did not distinguish between SIDS and explained SUDI. In the univariate analysis many of the epidemiologic characteristics significant among the SIDS group were also identified and in the same direction among the infants dying as SUDI attributable to known causes. The explained deaths were similarly characterized by the same infant, maternal, and social factors, 48% of these families received no waged income. Using logistic regression to make a direct comparison between the two index groups there were only three significant differences between the two groups of deaths: 1) a different age distribution, the age distribution of the explained deaths peaked in the first 2 months and was more uniform thereafter; 2) more congenital anomalies were noted at birth (odds ratio [OR] = 3.14; 95% confidence intervals [CI]: 1.52–6.51) among the explained deaths (20%) compared with the SIDS (8%), which was not surprising given that 10% of these deaths were explained by congenital anomalies; and 3) a higher incidence of maternal smoking during pregnancy among the SIDS mothers, the proportion of smokers within the explained SUDI group was much higher (49%) than the controls (27%), but among SIDS mothers the proportion of smokers was higher still (66%) and this difference was significant (66% vs 49%; OR = 2.03; 95% CI: 1.16–3.54). The largest subgroup of explained SUDI deaths were those attributable to infection (46%). There was a winter peak of deaths from infection, the highest number occurring in December (21%) but this was not significant. A multivariate model of these deaths showed parental unemployment to be the most significant factor (OR = 27.74; 95% CI: 3.19–241.34). Short gestational age (OR = 11.67; 95% CI: 1.84–74.14), neonatal problems (OR = 14.27; 95% CI: 1.89–107.81), and higher prevalence of males (OR = 9.26; 95% CI: 1.63–52.52) were also significant. Half of the deaths from infection occurred in crowded households (>1 adult or child per room excluding hallways, toilets, bathrooms, and kitchens if not used as a dining room) which was also a significant factor (OR = 10.37; 95% CI: 1.08–99.59). Conclusions. The study identifies changes in the epidemiologic characteristics of SIDS that have followed the “Back to Sleep” campaign, and confirms that many underlying factors are similar between infants who die as SIDS and those dying suddenly of explained causes. Many studies investigating SIDS have reported numerous epidemiologic characteristics and risk factors strongly associated with SIDS when compared with live control infants. It has been generally assumed that these factors are specific to SIDS to the extent that the syndrome has been described as an “epidemiologic entity.” Many of the factors associated with SIDS that were significantly different from the control population were not significantly different when compared with the explained deaths. This suggests that SUDI share some of the same underlying factors irrespective of the clinical or pathologic findings, and challenges a rigid concept of SIDS as an epidemiologic entity. The particular finding that the incidence of maternal smoking during pregnancy, although high among mothers of explained SUDI infants, was significantly higher among SIDS mothers, lends weight to the mounting evidence that the association between smoking and SIDS may be part of a causal mechanism.

Can the fall in Avon's sudden infant death rate be explained by changes in sleeping position?

OBJECTIVE--To examine the impact of changing practice with regard to infant sleeping position on mortality from the sudden infant death syndrome. DESIGN--A population based study of all infants dying suddenly and unexpectedly during February 1990 to July 1991, and two groups of controls; one comprising every 125th baby born to Avon residents and the other comprising pairs of infants matched to each index case for age, neighbourhood, and date of study. Information about sleeping position was collected at home visits soon after the index babys death or, for the population based controls, on several occasions in the first six months of life. The design was comparable to that of an earlier study of the same population. SETTING--County of Avon. SUBJECTS--35 infants who died suddenly and unexpectedly (32 of the sudden infant death syndrome), 70 matched controls, and 152 population based controls. RESULTS--The prevalence of prone sleeping in the matched controls was much lower than that found in an earlier study in Avon (28% (18/64) 1990-1 v 58% (76/131) 1987-9; p less than 0.001) and was comparable with the prevalence in population based controls (29%). This would be expected to lead to a reduction in the incidence of the sudden infant death syndrome to 2.0/1000 live births (95% confidence interval 1.8/1000 to 2.5/1000). The actual mortality fell from 3.5/1000 in 1987-9 to 1.7/1000. CONCLUSION--The fall in mortality can be almost entirely accounted for by the reduction in prone sleeping, suggesting a causal relation exists between them. Side and supine positions confer protection but the side position is unstable and the infant may roll prone. We therefore recommend supine as the safest sleeping position for babies.

Pacifier use and sudden infant death syndrome: results from the CESDI/SUDI case control study

OBJECTIVES To investigate the relation between pacifier use and sudden infant death syndrome (SIDS). DESIGN Three year population based, case control study with parental interviews for each death and four age matched controls. SETTING Five regions in England (population > 17 million). SUBJECTS 325 infants who had died from SIDS and 1300 control infants. RESULTS Significantly fewer SIDS infants (40%) than controls (51%) used a pacifier for the last/reference sleep (univariate odds ratio (OR), 0.62; 95% confidence interval (CI), 0.46 to 0.83) and the difference increased when controlled for other factors (multivariate OR, 0.41; 95% CI, 0.22 to 0.77). However, the proportion of infants who had ever used a pacifier for day (66% SIDS v 66% controls) or night sleeps (61% SIDS v 61% controls) was identical. The association of a risk for SIDS infants who routinely used a pacifier but did not do so for the last sleep became non-significant when controlled for socioeconomic status (bivariate OR, 1.39 (0.93 to 2.07)). CONCLUSIONS Further epidemiological evidence and physiological studies are needed before pacifier use can be recommended as a measure to reduce the risk of SIDS. Key messages There was no difference between victims of SIDS and control infants in routine use of a pacifier (“dummy” or “soother”) for day or night sleeps The use of a pacifier was associated with a lower prevalence and shorter duration of breast feeding, lower socioeconomic status, and mothers who smoked more heavily There was no association between pacifier use and sleeping position More control infants used a pacifier for the last/reference sleep, giving an apparent “protective” effect against SIDS; the significance of this association increased when controlled for other factors Further epidemiological evidence and physiological studies are needed before we can recommend pacifier use as protective against SIDS

A clinical comparison of SIDS and explained sudden infant deaths: how healthy and how normal?

OBJECTIVES To compare the clinical characteristics associated with sudden infant death syndrome (SIDS) and explained sudden unexpected deaths in infancy (SUDI). DESIGN Three year population based, case control study with parental interviews for each death and four age matched controls. SETTING Five regions in England (population, > 17 million; live births, > 470 000). SUBJECTS SIDS: 325 infants; explained SUDI: 72 infants; controls: 1588 infants. RESULTS In the univariate analysis, all the clinical features and health markers at birth, after discharge from hospital, during life, and shortly before death, significant among the infants with SIDS were in the same direction among the infants who died of explained SUDI. In the multivariate analysis, at least one apparent life threatening event had been experienced by more of the infants who died than in controls (SIDS: 12% v 3% controls; odds ratio (OR) = 2.55; 95% confidence interval (CI), 1.02 to 6.41; explained SUDI: 15% v 4% controls; OR = 16.81; 95% CI, 2.52 to 112.30). Using a retrospective illness scoring system based on “Baby Check”, both index groups showed significant markers of illness in the last 24 hours (SIDS: 22%v 8% controls; OR = 4.17; 95% CI, 1.88 to 9.24; explained SUDI: 49% v 8% controls; OR = 31.20; 95% CI, 6.93 to 140.5). CONCLUSIONS The clinical characteristics of SIDS and explained SUDI are similar. Baby Check might help identify seriously ill babies at risk of sudden death, particularly in high risk infants. Key messages There are clinical features and health markers characterising increased vulnerability of infants who die suddenly and unexpectedly that are evident at birth, during life, and just before death These features, important among the infants with sudden infant death syndrome, are in the same direction among the explained sudden unexpected deaths Clinical features common to both groups of explained and unexplained deaths after controlling for possible confounders included a higher prevalence of an apparent life threatening event and ill health in the 24 hours before death “Baby Check” might help identify seriously ill babies at risk of sudden death, particularly in high risk infants

Weight gain and sudden infant death syndrome: changes in weight z scores may identify infants at increased risk

AIMS To investigate patterns of infant growth that may influence the risk of sudden infant death syndrome (SIDS). DESIGN Three year population based case control study with parental interviews for each death and four age matched controls. Growth was measured from prospective weight observations using the British 1990 Growth Reference. SETTING Five regions in England (population greater than 17 million, more than 470 000 live births over three years). SUBJECTS 247 SIDS cases and 1110 controls. RESULTS The growth rate from birth to the final weight observation was significantly poorer among the SIDS infants despite controlling for potential confounders (SIDS mean change in weight z score (δzw) = −0.38 (SD 1.40)v controls = +0.22 (SD 1.10), multivariate: p < 0.0001). Weight gain was poorer among SIDS infants with a normal birth weight (above the 16th centile: odds ratio (OR) = 1.75, 95% confidence interval (CI) 1.48–2.07, p < 0.0001) than for those with lower birth weight (OR = 1.09, 95% CI 0.61–1.95, p = 0.76). There was no evidence of increased growth retardation before death. CONCLUSIONS Poor postnatal weight gain was independently associated with an increased risk of SIDS and could be identified at the routine six week assessment. Key messages The lower weight of SIDS infants compared to the control infants which was apparent at birth was even more notable in the two weeks before death SIDS infants, particularly those of normal birth weight, exhibited poorer weight gain than their controls Although poor growth was evident among SIDS infants there was no evidence of accelerated retardation in the weeks prior to death The difference in growth between SIDS and control infants was apparent within the first five to seven weeks of life

Baby Check and the Avon infant mortality study.

Thirty seven sudden, unexpected infant deaths from the Avon study were scored retrospectively for serious illness using a modified version of Baby Check. Three cases (8%) scored very highly. In a small proportion of sudden deaths, Baby Check could have identified serious illness before death and led to hospital admission.