News Release from Children’s Hospital of Philadelphia
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PHILADELPHIA — Infants who sleep at night in a bedroom with a light on may be at higher risk for nearsightedness later in childhood. A collaborative study by researchers at the University of Pennsylvania Medical Center and The Children’s Hospital of Philadelphia found that children who slept with either a room light or night light on until age 2 were more likely to later develop myopia (nearsightedness), compared to children who slept in darkness. Graham E. Quinn, M.D., a pediatric ophthalmologist at Children’s Hospital, and Richard A. Stone, M.D., of Penn’s Scheie Eye Institute, announced their findings in the May 13 issue of Nature.
The researchers surveyed parents of 479 children aged 2 to 16 seen in the ophthalmology outpatient department of Children’s Hospital. A questionnaire asked about the child’s nighttime light exposure at the time of the survey and before age two. Only 10 percent of children who slept in darkness before age 2 currently had myopia, compared to 34 percent of children who had slept with a night light, and 55 percent of those who had a room light on. Light exposure after age two showed no such association with current myopia. “The results were dose-dependent,” said Dr. Quinn. “Room lights were associated with a higher likelihood of nearsightedness than four-watt night lights.”
Both family history and environmental factors are thought to be involved in causing myopia. “Myopia is largely a disorder of industrialized societies,” said Dr. Stone, adding that myopia raises the risk of retinal problems, glaucoma and blindness in later life. In myopia, images focus in front of the retina instead of directly on it, largely because the eye has grown too long after birth. Prior research had shown that the eyes of chicks require a daily period of darkness to grow normally, and the researchers thus decided to study nighttime light exposure in children. They specifically asked about light exposure in the first two years of childhood. The eye normally develops rapidly during the early years of life even though myopia is usually detected much later. “Lighting may have an influence during sleep because small amounts of light pass through the eyelids even when they are closed,” said Dr. Stone.
The researchers are preparing a follow-up study of some of the same children involved in the original research, to obtain precise measurements of the anatomy of the children’s eyes. Further studies in other populations are needed to determine whether the initial findings can be generalized. As for what parents should do, Dr. Quinn said that children below age 2 are not usually afraid of the dark, and that “until these research results are more thoroughly evaluated, babies should sleep without artificial lighting in the bedroom at nighttime.”
The Children’s Hospital of Philadelphia, the nation’s first children’s hospital, is a leader in patient care, education and research. This 406-bed multispecialty hospital provides comprehensive pediatric services to children from before birth through age 19. The Children’s Hospital of Philadelphia admits more than 16,00 patients and cares for more than 50,000 emergency and 500,000 outpatient visits annually.
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