| [ Summary ] |
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Human beings of homeothermic animals control
their body temperature constantly by regulating
thermogenesis and thermolysis against the
changes of environmental temperature. However,
hyperthermia (heat stroke) occurs easily
in sleeping infants, if the mechanism of
thermolysis (cooler) is remarkably inhibited
by a high-temperature environment or excessive
clothing. Adults can take appropriate means
against the unpleasant external environment.
However, it is impossible for infants to
turn over in their sleep, take off their
socks, or remove bedclothes by kicking, so
we must always care if their environments
are pleasant and ensure against risk. During
daytime, an infant is often observed by someone.
So his/her unusal condition (heat stroke)
is possible to detect earlier and SIDS can
be avoided. At night, however, the environment
surrounding of the infant is dark and his/her
parents are often sleeping, so detection
of disorder may be delayed and "heat
stroke" may result in the worst situation.
An infant with hyperthermia ("heat
stroke") in the cause of external environmental
factors has to suppress thermogenesis. Consequently,
he/she is obliged to sleep deeply, relax
the muscles, and decrease body movement in
order to keep his/her body temperature normal.
As a homeothermal animal, these behaviors
occur commonly. However, if the suppression
of thermogenesis lasts for a long time, it
may cause serious troubles in the life of
the sleepig infant.
To sum up, this new hypothesis suggests
that
SIDS tends to occur when the following
three
factors are overlapped each other. |
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| １）External environmental factors (nursing environment)
causing hyperthermia (heat stroke) |
| （１） |
Excessive clothing, such as caps, gloves,
and socks, and bedclothes
(disturbance of thermolysis).
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| （２） |
Lying prone in sleeping (disturbance of thermolysis
from the
abdomen which release the heat of infants,
higher than back). |
| （３） |
Long-time sleeping under a high-temperature
environment |
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(in bedclothes, inside warm car, near heater,
on hot carpet, in incubator, during bathing,
etc.) |
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| ２）Characteristics of (SIDS) infants |
| （１） |
Infants cannot give a "hazard signal(too
hot)" with word. |
| （２） |
Infants cannot escape from the unpleasant
external environment (high temperature). |
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| ３）Human beings are homeothermal animal. |
| （１） |
Infants with hyperthermia (heat stroke) keep
sleeping more deeply
and relax the muscles to inhibit
thier thermogenesis. |
| （２） |
Unless the situation with heat stroke is
improved, arousal reaction is
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retarded. Long-time deep sleeping and relaxation
of the muscles cause respiratory inhibition (hypoxemia). |
| （３） |
According to the rise of environmental temperature,
oxygen
consumption of infants increases. |
| （４） |
Release of catecholamines is suppressed during
peripheral
vasodilation, especially during sleep. |
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| The above-mentioned characteristics, 2. and
3. are those of human infants. We adults
should pay attention to the item 1. It is
the most important for us to understand these
characteristics of infants thoroughly, and
to give them safe and comfortable environments. |
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The new hypothesis described above may not
be suitable completely for all the cases
of SIDS. In this study, the investigations
of central(core) and peripheral deep body
temperatures of infants could clarify the
thermo-control mechanisms of infants, and
the risk of prone-sleeping for SIDS. Nevertheless,
it must be necessary to carry out further
studies in order to make more clear actual
contrivances(=mechanisms) of neuro-regulaion
center of temperature and respiration, and
other mechanisms of infants. Furthermore,
it must be clarified the reasons hastely
and scientifically why the bottle-feeding
and the smoking, as remained risk factors
for SIDS, are dangerous for infants.
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