The study, published in the May issue of the Journal of Perinatology, is believed to be the first to demonstrate a link between retinopathy of prematurity (ROP), a condition marked by abnormal blood vessel growth in the retina, and hyperglycemia, which occurs in about 45 percent of all infants weighing less than 2.2 lbs.
The Johns Hopkins researchers found that infants with ROP had higher daily blood sugar levels compared to healthy infants of the same gestational age and birth weight, and determined that with each 10 mg/dl increase of average monthly glucose levels, ROP risk almost doubled.
"We were not surprised by these study results, especially since ROP bears many similarities to adult diabetic retinopathy, a related retinal disorder in which hyperglycemia has already been shown to be a major risk factor," said the study's senior author, Christoph U. Lehmann, M.D., a Children's Center neonatologist. "If glucose is truly connected to the pathogenesis of ROP, as our study finds, then we may be able to reduce the risk using tighter glucose control in the first few months of life."
Hopkins researchers examined the charts of 16 preemies born at The Johns Hopkins Hospital between 1992 and 1997 who developed ROP, and compared them to 31 healthy infants based on gestational age, birth weight and year of birth.
Initial ophthalmologic screening was performed on all infants within six weeks of birth. During the first month of life, an average of five glucose measurements were taken per day to calculate daily maximum, minimum, mid-point and average values for each individual infant.
ROP infants had higher glucose maximums, averages and mid-point levels than control infants. Their daily glucose levels also varied more, with average measurements ranging from a low of 78 mg/dl to a high of 116 mg/dl. Additionally, ROP infants experienced hyperglycemic events – or glucose levels above 150 mg/dl – more often than the control group. According to researchers, normal glucose levels in infants should range between 60 mg/dl and 150 mg/dl.
The study also affirmed the well-established link between high oxygen levels and ROP, with researchers finding infants at increased risk for ROP with even the smallest increases of supplemental oxygen, which is almost always given to preemies. Other known ROP risk factors include blood transfusions, frequent blood gas measurements and ventilator use.
However, Lehmann said further research is needed before hyperglycemia can be considered an independent ROP risk factor or a cause of the disease. "Although we saw an association between hyperglycemia and ROP, we need additional studies to confirm our findings and determine if hyperglycemia is inherently linked to ROP or if it represents another marker of severity of illness, such as the number of blood transfusions," he said.
Co-authors on the study were Ruchira Garg, M.D., Alexander Agthe, M.D., and Pamela Donohue, M.D., of the Division of Neonatal-Perinatal Medicine at the Children's Center.
Johns Hopkins Medical Institutions' news releases are available on an EMBARGOED basis on EurekAlert at http://www.eurekalert.org, and from the Office of Communications and Public Affairs' direct e-mail news release service. To enroll, call 410-955-4288 or send e-mail to bsimpkins@jhmi.edu. On a POST-EMBARGOED basis find them at http://www.hopkinsmedicine.org
Journal
Journal of Perinatology