The Sudden Infant Death Syndrome Alliance
1314 Bedford Avenue
Suite 210
Baltimore, Maryland 21208     # 410-653-8226        # 800-221-7437



TO: Affiliate Presidents and Executive Directors
FROM: Judith S. Jacobson, Executive Vice President
DATE: 4/2/01

RE: "Thermal Stress in Sudden Infant Death. Is There an Ambiguity With the
Rebreathing Hypothesis?" Pediatrics Vol. 107 No. 4, April 2001

In the April 2001 issue of Pediatrics, Warren G. Guntheroth, MD and Philip S. Spiers, PhD,
compare the risk factors for infant's overheating with those of rebreathing and determine
that both share some common clinical markers and pose a risk for Sudden Infant Death
Syndrome. They conclude that it is important that health care professionals and others
who interact with new parents continue to focus on maintaining a comfortable room
temperature for the baby and avoid overheating. The article, "Thermal Stress in Sudden
Infant Death. Is There an Ambiguity With the Rebreathing Hypothesis?" states that - in
addition to placing an infant to sleep on his or her back - SIDS could be further reduced
by not wrapping an infant in excessive bedclothes or by covering its head during sleep.

The authors chronicle a history of medical research on parents' practices in creating a
sleep environment for their infants, reinforcing the importance of placing babies on their
backs for sleep. An infant's ability to retain body heat is significantly increased by stomach
sleeping; the main source of heat loss is the baby's head - particularly the face. If that is
also covered, overheating is even more likely. Challenged by thermal stress, an infant's
heart, lung and sweat glands must work harder to cool down. Guntheroth and Spiers
suggest that SIDS risk as it relates to seasonality, infection, and the effects of bedsharing
are consistent with the overheating hypothesis. In colder months, parents may dress an
infant in more layers or with warmer blankets. An infant with a fever needs less as opposed
to more insulation from clothing because his body temperature is already elevated. Studies
have shown that an infant frequently has its head covered when bedsharing, as well as the
heat source provided by the mother's body under shared blankets.

Since the launch of the Back to Sleep Campaign in 1994, the primary message for parents
and other caregivers has been to place infants to sleep on the back to help reduce the risk
of SIDS. Through multiple research studies from around the world, stomach sleeping had
been indicated to create the greatest risk for SIDS. At the same time, further risk reduction
recommendations have been provided, including the use of a firm, flat mattress; elimination
of fluffy, loose bedding and soft objects from the infant's sleep environment; maintenance
of a smoke-free zone around the baby; and the avoidance of infant overheating due to
excessive bed clothes or room temperature.

Consistent with the Guntheroth and Spiers study, the SIDS Alliance brochure, Facts About
Sudden Infant Death Syndrome & Reducing the Risk of SIDS cautions parents to be careful
not to overheat their baby. "Research findings indicate that overheating (too much clothing, too
heavy bedding, and too warm a room) may increase the risk of SIDS, particularly if a baby
already has a fever. Other signs that your baby may be overheated include sweating, damp hair,
heat rash, rapid breathing, and restlessness. Babies cannot regulate their own body temperature
well, therefore, parents should set the thermometer to whatever temperature you find most
comfortable and dress your baby in as much or as little as you would wear. Remember to
remove your baby's hat and heavy outerwear when indoors, in cars, or stores to keep your
baby from becoming overheated during the cold weather months, and limit layers of clothes
and blankets in warmer weather."

While we acknowledge overheating as a risk factor and encourage parents to avoid
overdressing their babies for sleep, it is important to note that studies have also found an
increased SIDS risk among infants who were wearing too little clothing while sleeping in a
cool environment.

Although we do not yet know exactly how or why SIDS happens, researchers continue
to identify deficits, behaviors, and other factors that may put an infant at higher risk. It is
important to remember that risk factors are not causes of SIDS, but are believed to make
an infant more vulnerable and increase the possibility of death. SIDS, like other medical
disorders, may eventually have more than one explanation and more than one means of
prevention. Multiple and different risk factors may play a role in a particular infant's death.
At the same time, many SIDS victims have no known risk factors; and most babies with one
or more risk factors will survive. Research must continue if we are to discover what causes
SIDS, and expand upon opportunities to reduce SIDS risk.

According to Bradley Thach, MD, Professor of Pediatrics at the Washington University
School of Medicine in St. Louis and chairman of the SIDS Alliance Medical and Scientific
Advisory Council, the Back to Sleep recommendations continue to provide parents and
care givers with the latest medical evidence on reducing the risk of SIDS in the hope of giving
every baby the best possible chance to thrive. Dr. Thach reminds parents and other caregivers to:

· Place your baby on the back to sleep at night and naptime.

· Use a firm mattress in a safety-approved crib or bassinet.

· Eliminate fluffy, loose bedding from your baby's sleep area.

· Keep your baby's face clear of coverings.

· Be careful not to overheat your baby.

· Don't allow anyone to smoke around your baby.

· Educate babysitters, day care providers, grandparents and everyone who cares for
  your baby about SIDS risk.

· And don't forget to enjoy your new baby!

The SIDS Alliance is a national, not-for-profit, voluntary health organization dedicated
to the support of SIDS families, public education, and medical research. For the latest,
quality-assured information about Sudden Infant Death Syndrome and ways to reduce
SIDS risk, call the SIDS Alliance toll-free at 1 (800) 221-SIDS (7437) or visit the SIDS
Alliance Online at

Click here to see a second article on SIDS.