and communities can help protect young people from
the harms of substance abuse.
See also: ADOLESCENCE; CONFORMITY; PARENT-
CHILD RELATIONSHIPS
Bibliography
Grant, Bridget F., and Deborah A. Dawson. ‘‘Age at Onset of
Alcohol Use and Its Association with DSM-IV Alcohol Abuse
and Dependence: Results from the National Longitudinal Al-
cohol Epidemiologic Survey.’’ Journal of Substance Abuse 9
(1997):103–110.
Johnston, Lloyd D., Patrick M. O’Malley, and Jerald G. Bachman.
Monitoring the Future National Survey Results on Drug Use,
1975–1999, Vol. 1: Secondary Students. Bethesda, MD: Nation-
al Institute on Drug Abuse, 1999.
Johnston, Lloyd D., Patrick M. O’Malley, and Jerald G. Bachman.
‘‘Monitoring the Future National Results on Adolescent Drug
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http://www.monitoringthefuture.org; INTERNET.
Kandel, Denise B., and Kazuo Yamaguchi. ‘‘From Beer to Crack:
Developmental Patterns of Drug Involvement.’’ American Jour-
nal of Public Health 83 (1993):851–855.
Kandel, Denise B., Kazuo Yamaguchi, and Kevin Chen. ‘‘Stages of
Progression in Drug Involvement from Adolescence to Adult-
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Denise Hallfors
Laura E. Frame
SUDDEN INFANT DEATH SYNDROME
Sudden infant death syndrome (SIDS) refers to the
sudden unexpected death of an infant under the age
of one year who prior to the event was considered to
be completely healthy. The diagnosis also requires
that a review of the clinical and environmental histo-
ry, death scene investigation, and autopsy fail to re-
veal an alternative explanation of the death. In other
words, the diagnosis of SIDS remains a diagnosis of
exclusion.
Incidence
SIDS remains the primary cause of death for in-
fants between one month and six months of age. Prior
to 1991 the incidence rates of SIDS in the United
States ranged between 1.2 and 2 per 1,000 live births.
Of the developed countries of the world, some, in-
cluding Sweden, Hong Kong, and Japan, reported
rates as low as 0.3 to 0.5 per 1,000 live births. Others,
such as Australia (especially Tasmania), New Zealand,
and Northern Ireland reported rates as high as 3–7
per 1,000 live births. In 1995, three years after the
Academy of Pediatrics issued guidelines recommend-
ing placing infants in the nonprone position (i.e., not
lying on the stomach) for sleeping, Michael Malloy
and his colleagues published a study noting a 33 per-
cent drop in the incidence of SIDS within the United
States. Other countries reported similar experiences
after adopting infant sleep position changes. This
lowered incidence was maintained for succeeding
years, but it remains to be seen if additional decreases
will occur with increasing compliance with the recom-
mended sleep positioning guidelines.Epidemiological Factors
While the cause of SIDS remains elusive, multiple
studies have documented consistent epidemiological
factors associated with higher SIDS risks in some
groups of infants. Risk factor categories include ma-
ternal and prenatal, neonatal (newborn), postneona-
tal, geographic, and race/ethnicity groupings.
Maternal and prenatal risk factors constitute a
lengthy list of biological and environmental condi-
tions. These include shorter interpregnancy interval,
increased placental weight, low socioeconomic status,
nutritional deficiency, anemia, urinary tract infection,
intrauterine hypoxia (oxygen deficiency), fetal
growth retardation, smoking, drug exposure, poor
prenatal care, young age, lower education, and in-
creased number of pregnancies. Several studies have
identified maternal smoking as a significant risk fac-
tor. The National Institute of Child Health and
Human Development (NICHD) conducted a large
study in the United States of 757 SIDS cases with two
matched control groups. Seventy percent of the SIDS
mothers in this study smoked. When compared with
the control groups, the risk for infants of mothers who
smoked is doubled and progressively increases as the
number of cigarettes smoked per day increases.
These infants also die at younger ages. Constriction
of blood vessels leading to chronically diminished ox-
ygen delivery to fetal tissues is thought to be the
mechanism by which smoking increases the risk of
SIDS.
Neonatal risk factors include poor growth, as-
phyxia (inadequate oxygen delivery to body tissues),
prematurity, and low birthweight. As the gestational
age decreases, the relative risk of SIDS increases. This
is also true of birthweight. The incidence of SIDS in
preterm infants whose birthweight is greater than
1,500 grams (3 pounds, 5 ounces) is about 8 per 1,000
live births, compared to preterm infants with birth-
weights less than 1,500 grams, where the risk rises to
10 per 1,000 live births. Postnatally, male sex, age
(two to four months), bottle feeding, overheating,
smoking exposure, soft bedding materials, no pacifier
use, and prone sleeping position have been identified
as significant factors that independently increase the
risk of SIDS.394 SUDDEN INFANT DEATH SYNDROME