SIDS—changes in the epidemiological pattern in Eastern Norway 1984–1996

doi:10.1016/S0379-0738(98)00048-6

Forensic Science International

Volume 93, Issues 2–3, 11 May 1998, Pages 155-166

https://doi.org/10.1016/S0379-0738(98)00048-6 Get rights and content

Abstract

The objective was to analyse differences in the epidemiological pattern of sudden death in infancy during two time periods—the Sudden Infant Death Syndrome (SIDS) `epidemic': 1984–1989, and the period of rapid decline in the SIDS rate 1990–1996. Sex distribution, age, sleeping position, signs of infection, day of the week and place of death were registered and compared for the two time periods studied in all SIDS cases autopsied at the Institute of Forensic Medicine, Oslo. There were significantly more deaths in the age group under four months in the period 1984–89 than in the second period. Prone sleeping position, signs of infection, death outdoors and during the winter were more frequent during the first period than in the second. These features also were more frequent in the age group under four months than in the older babies during the first period. The shift in the epidemiological pattern after 1990, when the risk factor campaign was launched, indicates that prone sleeping position, cold climate, sleeping outdoors and infections seem to be risk factors that are particularly harmful to the youngest infants.

Introduction

During the eighties, Norway experienced a Sudden Infant Death Syndrome (SIDS) epidemic [1]. In 1984–1989, the SIDS rate in Eastern Norway reached peak values of approximately 2 per 1000 live births [2]. Since then, however, the rate has dropped dramatically being approximately 0.6 per 1000 live births after 1994. Other authors have reported the same decline in SIDS rate in other countries and several have pointed out that this decline has coincided with a change in sleeping position 3, 4, 5, 6, 7. During the seventies and eighties, the prone sleeping position became increasingly common in Norway [8], but at the end of 1989 a campaign against the prone position was started, and the decline in SIDS rate has been shown to run parallel to the decline in the prone sleeping position in the total infant population [7].

In 1984, a prospective study of sudden infant death was initiated at the Institute of Forensic Medicine in Oslo and between then and 1996, a total of 281 deaths in infants and children under two years of age have been examined by autopsy.

The purpose of this study was to compare characteristics such as age and sex distribution, position when found dead, information about infections prior to death, place and day of the week of death, which had been registered in the period with high rates, between 1984 and 1989, with those registered in the period with lower rates, between 1990 and 1996 [1].

Some of these factors, such as prone position, increased body temperature (due to too much clothing or infection) have been established as risk factors [9]that can be eliminated, whereas others, such as gender, age, seasonal variation or signs of infection, cannot be manipulated.

The aim of the study was to elucidate shifts in the epidemiological patterns to generate hypotheses for studies of trigger mechanisms and death mechanisms.

Section snippets

Forensic autopsies in eastern Norway

The Institute of Forensic Medicine in Oslo serves eastern Norway which includes 9 out of 19 counties in the country. The population is 2.2 million which is 51 percent of the total population. Practically all criminal cases are investigated at the institute in Oslo. Other forensic cases, such as accidents and sudden unexpected deaths are also investigated by clinical pathologists. The proportion of forensic cases examined by others rather than by forensic experts has declined from 19% in 1984 to

Results

The sex distribution was the same in both periods, the ratio male/female being 59/43 and 57/41 in the first and second periods, respectively. The age distribution in the two periods was significantly different (P<0.01), and the differences appear to lie in the youngest group, the typical age peak between two and four months being less pronounced in the second period (Fig. 2). Thus, the decrease was most pronounced in this age group. There were significantly more deaths in the age group <4

Discussion

The reason that the number of SIDS cases in the two periods studied is similar in spite of the drop in SIDS rate after 1990 is due to the fact that the second period is one year longer than the first one, and also that the decrease in SIDS rate has been compensated by the fact that other hospitals in the area have stopped to perform autopsies in cases of sudden infant death. However, the ratio between cases originating from urban and rural areas has not changed, constituting 21% and 79% in the

Acknowledgements

The authors wish to express their thanks to professor Robert Carpenter for his advices concerning the statistical calculations. This work was supported by the Norwegian SIDS Society and the Research Council of Norway.

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SIDS—changes in the epidemiological pattern in Eastern Norway 1984–1996

Abstract

Introduction

Section snippets

Forensic autopsies in eastern Norway

Results

Discussion

Acknowledgements

Lancet

J. Paediatr.

Lancet

Use of new Nordic criteria for classification of SIDS to reevaluate diagnoses of sudden unexpected infant death in the Nordic countries

Acta Paediatr.

Sleeping position for infants and cot death in the Netherlands 1985–91

Arch. Dis. Child

Cot death supplement. Results from the first year of the New Zealand cot death study

NZ Med. J.

Sociodemographic factors associated with sleeping position and location

Arch. Dis. Child

Sleeping position and sudden infant death syndrome in Norway 1967–91

Arch. Dis. Child

Sleeping position and sudden infant death syndrome in Norway

Tidsskr Nor Lœgeforen

Factors potentiating the risk of sudden infant death syndrome associated with the prone position

N. Eng. J. Med.

Cot death in eastern part of Norway 1984–92

Tidsskr Nor Lœgeforen

Sleeping position and sudden infant death syndrome (SIDS): effect of an intervention programme to avoid prone sleeping

Acta Paediatr.

Reduction in mortality from sudden infant death syndrome in New Zealand: 1986–92

Arch. Dis. Child

Environment of infants during sleep and risk of the sudden infant death syndrome: results of 1993–5 case-control study for confidential inquiry into stillbirths and deaths in infancy

Br. Med. J.