Historias Clinicas

Lisonkova et al. BMC Pregnancy and Childbirth 2012, 12:59 http://www.biomedcentral.com/1471-2393/12/59

RESEARCH ARTICLE

Open Access

Sudden infant death syndrome: a re-examination of temporal trends
Sarka Lisonkova1*, Jennifer A Hutcheon1 and KS Joseph1,2
Abstract
Background: While the reduction in infants’ prone sleeping has led to a temporal decline in Sudden Infant Death Syndrome(SIDS), some aspects of this trend remain unexplained. We assessed whether changes in the gestational age distribution of births also contributed to the temporal reduction in SIDS. Methods: SIDS patterns among singleton and twin births in the United States were analysed in 1995–96 and 2004– 05. The temporal reduction in SIDS was partitioned using the Kitagawa decomposition method into reductions dueto changes in the gestational age distribution and reductions due to changes in gestational age-specific SIDS rates. Both the traditional and the fetuses-at-risk models were used. Results: SIDS rates declined with increasing gestation under the traditional perinatal model. Rates were higher at early gestation among singletons compared with twins, while the reverse was true at later gestation.Under the fetuses-at-risk model, SIDS rates increased with increasing gestation and twins had higher rates of SIDS than singletons at all gestational ages. Between 1995–96 and 2004–05, SIDS declined from 8.3 to 5.6 per 10,000 live births among singletons and from 14.2 to 10.6 per 10,000 live births among twins. Decomposition using the traditional model showed that the SIDS reduction among singletonsand twins was entirely due to changes in the gestational age-specific SIDS rate. The fetuses-at-risk model attributed 45% of the SIDS reduction to changes in the gestational age distribution and 55% of the reduction to changes in gestational age-specific SIDS rates among singletons; among twins these proportions were 64% and 36%, respectively. Conclusion: Changes in the gestational agedistribution may have contributed to the recent temporal reduction in SIDS. Keywords: SIDS, Temporal trend, Gestational age

Background Although Sudden Infant Death Syndrome (SIDS) is a leading cause of post-neonatal death in industrialized countries, its etiology is largely unknown [1]. While the reduction in prone sleeping following the back-to-sleep campaign has led to a decline in SIDS in manycountries [2-6], there are several puzzling aspects related to this intervention and the epidemiology of SIDS. For instance, the onset of the decline in SIDS preceded the initiation of the back-to-sleep campaign [2-7]. The reduction in SIDS in the United States began in 1989, while the backto-sleep campaign was initiated in 1994 [6]. Similarly,
* Correspondence: slisonkova@cfri.ca 1 Department ofObstetrics & Gynaecology, University of British Columbia and the Women’s Hospital and Health Centre of British Columbia, Room E418B, 4480 Oak Street, Vancouver, BC V6H 3 V4, Canada Full list of author information is available at the end of the article

SIDS rates in the United Kingdom decreased continuously from 1988 onwards, while the back-to-sleep campaign only began in 1991 [7]. Other unexplainedepidemiologic features of the temporal reduction in SIDS include the relatively greater reduction in SIDS among term infants, as compared with infants born at preterm gestation. Data from Avon county in England show that term live births among SIDS cases decreased from 88% in 1984–88 to 63% in 1994–98, the period when SIDS rates declined most rapidly. The proportion of term infants among SIDS casesremained stable thereafter (66% in 1999–2003) and SIDS rates did not change dramatically during this period [7]. Also, a larger decline in SIDS was observed among twins as compared with singletons. In England, SIDS among twin live births declined by 71% from 1.4 per 1000 live births in 1993 to 0.4 per 1000 live births in 2003,

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