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Effects of docosahexaenoic acid supplementation on visual acuity and visual attention of preterm infants
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EFFECTS OF DOCOSAHEXAENOIC ACID SUPPLEMENTATION ON VISUAL ACUITY AND VISUAL ATTENTION OF PRETERM INFANTS Susan E. Carlson and Susan H. Werkman The University of Tennessee, Memphis, Newborn Center, 853 Jefferson Avenue, Memphis, TN 38163 Docosahexaenoic acid (DHA) is a member of the n-3 family of fatty acids that derive from the nutritionally essential n-3 fatty acid, linolenic acid (LNA). DHA but not LNA is found as a high percentage of total fatty acids in the retina and neurally active tissue. Neuringer and her colleagues have demonstrated that n-3 deficient diets decrease retinal and neural DHA accumulation with adverse effects on retinal physiology, visual development, and visual attention in rhesus monkeys. Human infants receive preformed DHA from their mothers during the last intrauterine trimester and in subsequent feedings of mothers’ milk. Infants born early in the last trimester and fed formulas prepared in the United States receive little preformed DHA but have good intakes of LNA. Although their diets are not n-3 deficient, we have postulated that they may need dietary DHA for optimal visual and neural development. If DHA were a “conditionally essential” nutrient for preterm infants, the inclusion of DHA in their diet might enhance outcomes related to n-3 status in rhesus monkeys; i.e., retinal physiology, visual development and visual attention. We studied early visual development and visual attention in two randomized, double-blind trials. Infant formulas containing LNA with DHA were compared with formulas containing LNA alone. Grating acuity, visual recognition memory and visual attention were determined within narrow age limits at 0, 2, 4, 6, 9 and 12 mo. Grating acuity was determined by the Teller Acuity Card procedure at each of these ages. At 6,9 and 12 mo visual recognition memory (novelty preference) and visual attention (look number and duration) were determined using the Fagan Infantest. In preterm infants supplemented with DHA for 11 mo (from -2 mo to 9 mo, Trial I), grating acuity was higher than in controls at 2 mo and 4 mo only. At 6, 9 and 12 mo, however, infants fed LNA+DHA compared with LNA alone had a higher number of total looks and looks to both the novel and the familiar stimuli and lower average time per look and time per novel look. In preterm infants supplemented with DHA for 5 mo (from -3 mo to 2 mo, Trial II), grating acuity was increased at 2 mo only and only in infants without bronchopulmonary dysplasia (BPD). At 12 mo the effects of DHA supplementation on look number and duration were similar to those seen at 12 mo in our first study regardless of whether or not the infant had BPD. Eighty-four infants had assessments for visual acuity at 2 mo, RBC DHA at 2 mo and visual attention at 12 mo. There was no relationship between 2-mo acuity and shorter look duration at 12 mo; however, RBC DHA at 2 mo (DHA feeding) and combined years of parent formal education were highly inversely related to look duration. In summary DHA supplementation increased grating acuity early in infancy and shortened look duration later in infancy. Prior and concurrent measures of resolution acuity were unrelated to look duration at 12 mo. We are inclined to interpret differences in look duration as evidence of differences in information processing speed. In conclusion the results of two randomized, double-blind trials in preterm infants show effects of dietary DHA on visual acuity and visual attention (look duration) analogous to those related to better DHA status in infant monkeys, suggestive evidence that DHA is a “conditionally essential” nutrient for preterm infants.
EFFECTS OF DOCOSAHEXAENOIC ACID SUPPLEMENTATION ON VISUAL ACUITY AND VISUAL ATTENTION OF PRETERM INFANTS Susan E. Carlson and Susan H. Werkman The University of Tennessee, Memphis, Newborn Center, 853 Jefferson Avenue, Memphis, TN 38163 Docosahexaenoic acid (DHA) is a member of the n-3 family of fatty acids that derive from the nutritionally essential n-3 fatty acid, linolenic acid (LNA). DHA but not LNA is found as a high percentage of total fatty acids in the retina and neurally active tissue. Neuringer and her colleagues have demonstrated that n-3 deficient diets decrease retinal and neural DHA accumulation with adverse effects on retinal physiology, visual development, and visual attention in rhesus monkeys. Human infants receive preformed DHA from their mothers during the last intrauterine trimester and in subsequent feedings of mothers’ milk. Infants born early in the last trimester and fed formulas prepared in the United States receive little preformed DHA but have good intakes of LNA. Although their diets are not n-3 deficient, we have postulated that they may need dietary DHA for optimal visual and neural development. If DHA were a “conditionally essential” nutrient for preterm infants, the inclusion of DHA in their diet might enhance outcomes related to n-3 status in rhesus monkeys; i.e., retinal physiology, visual development and visual attention. We studied early visual development and visual attention in two randomized, double-blind trials. Infant formulas containing LNA with DHA were compared with formulas containing LNA alone. Grating acuity, visual recognition memory and visual attention were determined within narrow age limits at 0, 2, 4, 6, 9 and 12 mo. Grating acuity was determined by the Teller Acuity Card procedure at each of these ages. At 6,9 and 12 mo visual recognition memory (novelty preference) and visual attention (look number and duration) were determined using the Fagan Infantest. In preterm infants supplemented with DHA for 11 mo (from -2 mo to 9 mo, Trial I), grating acuity was higher than in controls at 2 mo and 4 mo only. At 6, 9 and 12 mo, however, infants fed LNA+DHA compared with LNA alone had a higher number of total looks and looks to both the novel and the familiar stimuli and lower average time per look and time per novel look. In preterm infants supplemented with DHA for 5 mo (from -3 mo to 2 mo, Trial II), grating acuity was increased at 2 mo only and only in infants without bronchopulmonary dysplasia (BPD). At 12 mo the effects of DHA supplementation on look number and duration were similar to those seen at 12 mo in our first study regardless of whether or not the infant had BPD. Eighty-four infants had assessments for visual acuity at 2 mo, RBC DHA at 2 mo and visual attention at 12 mo. There was no relationship between 2-mo acuity and shorter look duration at 12 mo; however, RBC DHA at 2 mo (DHA feeding) and combined years of parent formal education were highly inversely related to look duration. In summary DHA supplementation increased grating acuity early in infancy and shortened look duration later in infancy. Prior and concurrent measures of resolution acuity were unrelated to look duration at 12 mo. We are inclined to interpret differences in look duration as evidence of differences in information processing speed. In conclusion the results of two randomized, double-blind trials in preterm infants show effects of dietary DHA on visual acuity and visual attention (look duration) analogous to those related to better DHA status in infant monkeys, suggestive evidence that DHA is a “conditionally essential” nutrient for preterm infants.