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Shedding Light on Premature Infant Health

Study suggests 'preemies' do better when exposed to cycled light

THURSDAY, Feb. 21, 2002 (HealthDayNews) -- The dark, quiet surroundings thought to promote fetal development in the womb may not work once an infant enters the real world -- particularly if that entry comes sooner than expected.

So suggests a new study published in the current Journal of Pediatrics.

Recreating the dark, intimate environment of a mother's womb was once thought beneficial for babies born prematurely, but this latest study says fragile infants may do better when exposed to naturally cycled light.

"Once the pre-term infant is born, it has different physiologic demands that are not like the womb," explains Debra H. Brandon, study author and assistant professor at the Duke University School of Nursing.

In the uterus, babies don't have to use their lungs to oxygenate their body. Likewise, the kidneys don't face the same demands and the digestive system does not have to work, she adds.

Once born, a baby's systems must function independently of the mother, and here's where Brandon says exposure to light can be critical.

"Cycled light probably promotes the development of circadian rhythms, which may, in turn, aid digestion, through the secretion of digestive enzymes, and the development of sleep-wake states," Brandon explains.

If pre-term infants can use their food better and sleep more, she says, they should gain weight faster, and the study showed they did.

A circadian rhythm is the internal clock that controls many body functions. It can be influenced by environmental cues, particularly light and darkness. Although our world runs on a 24-hour cycle, circadian rhythms can run anywhere from 22 to 28 hours in length.

In the womb, babies are connected to their mother's circadian rhythm. When born full-term, they quickly begin to develop their own internal body clock. Infants born prematurely, however, fall somewhere in the middle, and receive treatments that vary widely, Brandon says.

In many neonatal units, babies are continuously exposed to bright hospital light, which can be stressful, or relegated to near darkness, to simulate conditions in the womb. Neither, she says, is conducive to developing circadian rhythms.

At New York University Medical Center, doctors help premature infants by integrating light therapy into a unique form of treatment known as "Kangaroo Care," says Dr. Karen Hendricks-Munoz, director of the neonatal care program. Babies are taken out of incubators and placed on the bare chest of either parent for up to three hours at a time, using the warmth and "rhythm" of Mom or Dad's body to encourage growth and development.

"'Kangaroo Care' allows our premature infants to be held and touched regularly, which, naturally places them in a variety of lighting conditions and exposes them to other environmental cues. And we see a real difference in how well they do," Hendricks-Munoz says.

The idea that scientific attention is now being paid to these "non-medical cues" is important, she says.

"I think it's wonderful that an institution as prestigious as Duke has done this study, and given us the science behind one of the many things that we intuitively have always believed was right for the baby," Hendricks-Munoz says.

The Duke study involved 62 infants, all premature and all of similar weight. Babies were randomly assigned to one of three groups. The first group received cycled light every day soon after birth. The second group had 24 hours daily of near darkness soon after birth, followed by cycled light beginning at 32 weeks post-conceptual age -- equal to the gestational age if the baby had not been born prematurely. The third group also had near darkness almost from birth, followed by cycled light starting at 36 weeks post-conceptual age, not long before the infants went home.

The cycles were defined as 11 hours of light, followed by 11 hours of darkness. The near darkness was interrupted with some transitional lighting that occurred with each change in nursing shifts. All babies were weighed and measured daily, and vital signs were recorded regularly.

The result:Those infants who received the cycled light from birth, as well as those exposed beginning at 32 weeks, gained more weight and were considered heartier than the babies who remained in near darkness until just before going home.

There was no difference among the three groups, however, in ventilator use or length of hospital stay.

For Hendricks-Munoz, the study results are valuable. They dovetail with her research, which found that "not only exposure to light, but also touch and sound, can make a tremendous difference in how well a premature infant thrives."

Using "Kangaroo Care," premature infants often go home up to 20 days sooner than those who receive traditional care, she says.

What To Do: To learn more about circadian rhythms, visit the Red River Sleep Center. For more information on caring for premature infants, see The American Academy of Family Physicians. To find out more about "Kangaroo Care," visit The University of Manitoba.

SOURCES: Interviews with Debra H. Brandon, R.N., Ph.D., assistant professor, Duke University School of Nursing, and clinical nurse specialist, Duke Intensive Care Nursery, Durham, N.C.; Karen Hendricks-Munoz, M.D., director, Neonatology Program, New York University Medical Center and Bellevue Hospital, New York City; February 2002 Journal of Pediatrics
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