Nordic Epidemiological Sudden Infant Death Syndrome Study Research Articles

Sudden infant death syndrome during low incidence in Sweden 1997–2005

Following the change from prone to supine in preferred sleeping position, the incidence of Sudden Infant Death Syndrome (SIDS) in Sweden fell from 1.1 per 1000 live births in 1992 to 0.41 in 1995. After a further small decline, we have been experiencing a plateau at around 0.25 since 2000. To identify the changes that have occurred in the epidemiology of SIDS since the end of the Nordic Epidemiological SIDS Study in 1995. Data from the Medical Birth Register of Sweden, covering the years 1995-2005, were used. Sleeping position is not included in the register. The incidence of SIDS has remained low in Sweden. Independent risk factors were smoking during early pregnancy, parents not living together, low maternal age, high parity and short gestational age. The odds ratio for smoking has continued to increase and the median age of death has continued to decrease since the previous study. We found no signs of seasonality in the current material. Age at death continued to decrease. The high incidence during weekends persisted. Seasonality was not significant. There was no evidence of a changing effect from risk factors in the studied period.

SIDS risk factors and factors associated with prone sleeping in Sweden

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

Circadian variations in sudden infant death syndrome: associations with maternal smoking, sleeping position and infections. The Nordic Epidemiological SIDS Study

To study circadian variation in the sudden infant death syndrome (SIDS) and possible associations with risk factors for SIDS. A questionnaire-based case-control study matched for place of birth, age and gender was conducted in Denmark, Norway and Sweden: The Nordic Epidemiological SIDS Study. The study comprised 244 SIDS victims and 869 control infants between September 1992 and August 1995. The main outcome was hour found dead. A significant circadian pattern was observed among the 242 SIDS victims with a known hour found dead, with a peak at 08.00-08.59 in the morning (n = 33). Of the SIDS victims, 12% were found dead at 00.00-05.59, 58% at 06.00-11.59, 21% at 12.00-17.59 and 9.0% at 18.00-23.59. When comparing night/morning SIDS and day/evening SIDS (found dead 00.00-11.59 and 12.00-23.59, respectively), the proportion of night/morning SIDS was high among infants of smoking mothers (81% vs 53%, p < 0.001), infants with a reported cold (82% vs 64%, p = 0.007) and infants sleeping side/supine (81% vs 60%, p < 0.001). No associations were observed between hour found dead and other sociodemographic risk factors for SIDS. Risk (odds ratio and 95% confidence interval) of night/morning SIDS and day/evening SIDS was 7.0 (4.5-10.9) and 1.5 (0.8-2.5), respectively, for maternal smoking, 2.2 (1.5-3.1) and 0.6 (0.3-1.3), respectively, if the infant had a reported cold, 3.7 (2.1-6.6) and 3.1 (1.1-8.4), respectively, if the infant was put to sleep in the side position (supine reference), and 11.0 (5.9-20.2) and 21.6 (7.6-60.8), respectively, if the infant was put to sleep in the prone position. The observed higher proportion of night/morning cases in SIDS if the mother smoked, if the infant was reported to have a cold and if the infant was sleeping side/supine may contribute to the understanding of some epidemiological characteristics of SIDS.

Breast feeding and the sudden infant death syndrome in Scandinavia, 1992–95

Aims: To assess the effects of breast feeding habits on sudden infant death syndrome (SIDS). Methods: The analyses are based on data from the Nordic Epidemiological SIDS Study, a case–control...

Changes in the epidemiology of sudden infant death syndrome in Sweden 1973–1996

BACKGROUNDFrom the early 1970s to the early 1990s, there was a significant rise in the incidence of sudden infant death syndrome (SIDS) in Scandinavia. Following the risk reducing campaign, the...

Caffeine and alcohol as risk factors for sudden infant death syndrome

OBJECTIVETo assess whether alcohol and caffeine are independent risk factors for sudden infant death syndrome (SIDS).MATERIALS AND METHODSAnalyses based on data from the Nordic epidemiological SIDS study, a case control...

Interactions of infectious symptoms and modifiable risk factors in sudden infant death syndrome. The Nordic Epidemiological SIDS study

The aim of the study was to investigate the effect of infection on sudden infant death syndrome (SIDS) and to analyse whether modifiable risk factors of SIDS, prone sleeping, covered head and smoking act as effect modifiers. In a consecutive multicentre case‐control study of SIDS in Denmark, Norway and Sweden, questionnaires on potential risk factors for SIDS were completed by parents of SIDS victims, and for at least two controls matched for gender, age and place of birth. All SIDS cases were verified by an autopsy. The study comprised 244 SIDS cases and 869 controls, analysed by conditional logistic regression. Significantly more cases than controls presenting symptoms of infectious diseases during the last week and/or last day were treated with antibiotics and had been seen by a physician. The finding is consistent with the hypothesis of an infectious mechanism in SIDS induced by local microorganism growth and toxin or cytokine production, and also adds further support to a possible association between infection and SIDS by loss of protective mechanisms, such as arousal. The risk of SIDS among infants with the combined presence of infectious symptoms and either of the other modfiable risk factors, prone sleeping, head covered or parental smoking, was far greater than the sum of each individual factor. These risk factors thus modify the dangerousness of infection in infancy. □Cytokines, epidemiology, infectious symptoms, Nordic study, risk factors, SIDS, toxin

Interactions of infectious symptoms and modifiable risk factors in sudden infant death syndrome. The Nordic Epidemiological SIDS study.

The aim of the study was to investigate the effect of infection on sudden infant death syndrome (SIDS) and to analyse whether modifiable risk factors of SIDS, prone sleeping, covered head and smoking act as effect modifiers. In a consecutive multicentre case-control study of SIDS in Denmark, Norway and Sweden, questionnaires on potential risk factors for SIDS were completed by parents of SIDS victims, and for at least two controls matched for gender, age and place of birth. All SIDS cases were verified by an autopsy. The study comprised 244 SIDS cases and 869 controls, analysed by conditional logistic regression. Significantly more cases than controls presenting symptoms of infectious diseases during the last week and/or last day were treated with antibiotics and had been seen by a physician. The finding is consistent with the hypothesis of an infectious mechanism in SIDS induced by local microorganism growth and toxin or cytokine production, and also adds further support to a possible association between infection and SIDS by loss of protective mechanisms, such as arousal. The risk of SIDS among infants with the combined presence of infectious symptoms and either of the other modifiable risk factors, prone sleeping, head covered or parental smoking, was far greater than the sum of each individual factor. These risk factors thus modify the dangerousness of infection in infancy.

A case-control study of smoking and sudden infant death syndrome in the Scandinavian countries, 1992 to 1995

AIMTo establish whether smoking is an independent risk factor for sudden infant death syndrome (SIDS), if the effect is mainly due to prenatal or postnatal smoking, and the effect of...

Sociodemographic risk factors for sudden infant death syndrome: associations with other risk factors

The aim of this study was to investigate associations between sudden infant death syndrome (SIDS) and social factors in the Nordic countries. A case‐control study was conducted in Denmark, Norway and Sweden: The Nordic Epidemiological SIDS Study. Parents of 244 SIDS infants and 869 control infants matched on gender, age at death and place of birth filled in questionnaires. The dataset was analysed by conditional logistic regression. In univariate analysis, the following sociodemographic factors were associated with an increased risk of SIDS: low maternal age [odds ratio (OR) 7.8; 2.8‐21.5], high birth order (OR 4.4; 2.5‐7.5), single motherhood (OR 2.9; 1.7‐5.0), low maternal education (OR 4.5; 2.8‐7.1), low paternal education (OR 3.0; 1.9‐4.7), maternal unemployment (OR 2.4; 1.8‐3.4) and paternal unemployment (OR 4.0; 2.7‐5.9). In a multivariate analysis where maternal smoking was also included, only paternal unemployment, young maternal age and high birth order remained significantly associated with SIDS. Housing conditions were not associated with SIDS. However, the risk of SIDS was high if the family had lived in their present home for only a few years (OR 2.3; 1.3–4.1). Sociodemographic differences remain a major concern in SIDS in a low‐incidence situation and even in an affluent population with adequate health services.

Sociodemographic risk factors for sudden infant death syndrome: associations with other risk factors. The Nordic Epidemiological SIDS Study.

The aim of this study was to investigate associations between sudden infant death syndrome (SIDS) and social factors in the Nordic countries. A case-control study was conducted in Denmark, Norway and Sweden: The Nordic Epidemiological SIDS Study. Parents of 244 SIDS infants and 869 control infants matched on gender, age at death and place of birth filled in questionnaires. The dataset was analysed by conditional logistic regression. In univariate analysis, the following sociodemographic factors were associated with an increased risk of SIDS: low maternal age [odds ratio (OR) 7.8; 2.8-21.5], high birth order (OR 4.4; 2.5-7.5), single motherhood (OR 2.9; 1.7-5.0), low maternal education (OR 4.5; 2.8-7.1), low paternal education (OR 3.0; 1.9-4.7), maternal unemployment (OR 2.4; 1.8-3.4) and paternal unemployment (OR 4.0; 2.7-5.9). In a multivariate analysis where maternal smoking was also included, only paternal unemployment, young maternal age and high birth order remained significantly associated with SIDS. Housing conditions were not associated with SIDS. However, the risk of SIDS was high if the family had lived in their present home for only a few years (OR 2.3; 1.3-4.1). Sociodemographic differences remain a major concern in SIDS in a low-incidence situation and even in an affluent population with adequate health services.

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

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. 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. 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%. 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.