Sudden Infant Death Syndrome (SIDS)

Highlights of its Epidemiology and History

BIOS601: Dec. 5, 2007

SIDS: Introduction

• Definition: “The sudden death of an infant under one year of age which remains unexplained after thorough investigation, including the performance of a complete autopsy, examination of the death scene, and review of the clinical history”

• SIDS continues to be the leading cause of death for infants aged between 1 month and 1 year in developed countries:– Lowest: Japan (0.09/1000), The Netherlands (0.1/1000)

– Highest: New Zealand (0.8/1000)

– Intermediate: USA (0.57/1000), UK (0.41/1000)

– 2162 infants died of SIDS in the USA alone (2003).

• “An elusive disease that strikes not only the child, but his whole family”

NICHD (National Institute of Child Health & Human Development)

Issues of Definition

• “In the technical medical language, a ‘syndrome’ refers only to the set of detectable characteristics. A specific disease, condition, or disorder may or may not be identified as the underlying cause.” (Wikipedia)

• “… diagnosis of SIDS is a diagnosis of exclusion, and the means of exclusion are imperfect … a diagnostic dustbin” (Emery)

• “the diagnosis of cot death … excused all concerned from any defect in care, diagnosis, and treatment’ and ‘facilitated the development of parent support groups and the raising of money for research

• SIDS vs pneumonia (Loberg and Naess, 1991), 55% of 1,144 cases eliminated (Haas 1993),1.6% of 400 cases reclassified (Valdes-Dapena, 1988)

SIDS: Epidemiology

Age of Cot Deaths

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80

Age (Months)

# O

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(SIDS deaths, Auckland, New Zealand, 1970-1979)

Age Structure Seasonality

Month of Cot Deaths

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J F M A M J J A S O N D

Month of Year

# O

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- Gender, birth order, pacifiers, prior fetal loss, time of day, regional differences,race and ethnicity, family recurrence

- Cigarette smoking, bed-sharing, swaddling, breastfeeding, socioeconomic

SIDS: Pathology

Paradox: The baby is observed to be clean and well-cared-for with apparently good to excellent state of development, nutrition, and hydration.

External Findings: Moderate amount of cyanosis, mucoid fluid in the mouth and nostrils (> 50% of cases), soiled diapers

Internal Findings: Intrathoracic petechiae: observed more consistently in SIDS cases than in any other condition at this age (>50%), some pulmonary congestion and edema, some inflammation of the upper respiratory tract

SIDS: Final Pathways

Cardiovascular

Apnea

Mechanism

Epidemiology Pathology

Causality?

Hill’s Criteria …

SIDS Timeline

Old Testament (I Kings 3:19), Middle Ages

mid 1800s (rise and fall of thymic theory; negligence; other causes)

1942-1953 (Werne and Garrow, SIDS as a distinct medical entity)

1953+ (accumulation of epidemiologic and pathologic data, as wellas a ‘parade of theories’).

1969 (definition of SIDS established)

Early 1990s (identification of acceptance of sleeping position as the mostpowerful risk factor, followed by a worldwide decline in SIDS incidence)

2007 (still the leading cause of infant mortality, but with changing epidemiology)

Sleeping Position Timeline

1950-1985 – sleep position observed but not noticed in SIDS studies

1972 – public campaign in the Netherlands against the supine position

1985 – sleep position first clearly raised as a possible important factor(Davies, Hong Kong)

1986 – 1st study with clear recommendation against the prone sleepingposition (Beal), with subsequent drop in SIDS rates

1989 – 1st thorough analysis of the effects of the prone sleeping position(deJonge, Netherlands)

1991 – 1st prospective study of the prone position (Dwyer, Tasmania)

1991-1994 – controversy and delay in policy implementation in the United States

2007 – still the leading cause of infant mortality, but with changing epidemiology

1991-1994 SIDS controversy in the United States

• 1991 Guntheroth and Spier (JAMA)

• April 15, 1992 AAP press release followed by report in Pediatrics

• Criticisms: – Hunt and Shannon (1992)– SIDS Alliance (Mary Willinger)– Orenstein (1992)

• Sources of epidemiological controversy: statistics, literature,

causality vs. association, intuition, population differences,

iatrogenesis, levels of rigour. “Hindsight is 20/20”

• “willingness to ignore 2000-3000 infant deaths per year”

• National campaign announced by Surgeon General

AAP Task Force on Infant Positioning and SIDS (Pediatrics, 1992)

Four modifiable and other major risk factors for cot death: The New Zealand study

(Mitchell et. al., 1992)

SIDS rates in Avon compared with England and Wales, during 1984-2003

SIDS: An ongoing area of investigation

# SIDS articles (Pubmed)

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1970 1975 1980 1985 1990 1995 2000 2005 2010

Year

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6335 Hits

SIDS: An epidemiological study in progress

• Sudden infant death syndrome: another year of new hope but no cure.

(Curr Opin Pulm Med. 2007 Nov;13(6):497-504)• Risk of sudden infant death syndrome with parental mental illness.

(Arch Gen Psychiatry. 2007 Nov;64(11):1323-30 )• Unexpected sudden death related to medullary brain lesions

(Acta Neuropathol. 2005 May;109(5):554-5. Epub 2005 May 18)• Vitamin A and sudden infant death syndrome in Scandinavia 1992-1995.

(Acta Paediatr. 2003;92(2):162-4)• Enzyme-linked immunoassay for respiratory syncytial virus is not predictive of

bronchiolitis in sudden infant death syndrome.

(Pediatr Dev Pathol. 1998 Sep-Oct;1(5):375-9)• SIDS and chaos.

(Med Hypotheses. 1994 Jan;42(1):11-2)• Passive fear--a possible cause of sudden infant death?

(Tidsskr Nor Laegeforen. 1986 Apr 30;106(11):898-902)• Structure of periadrenal brown fat in childhood in both expected and cot deaths

(Arch Dis Child. 1978 Feb;53(2):154-8)• etc. …..

Conclusions

• Risk factors vs. causality (Hill’s criteria)

• Importance of policy in epidemiology

• Epidemiology changes

• Sources of epidemiological controversy

• Another breakthrough?

The continuing decline in SIDS mortality(Mitchell, 2007)