Reading difficulty in school-aged very low birth weight infants in Japan.

Objective: To investigate the prevalence of and the perinatal risk factors related to reading difficulty in school-aged very low birth weight infants (VLBWI) with normal intelligence.

Methods: Subjects were 79 Japanese children in the second to fourth grade of elementary school who had been born at very low birth weight and who regularly visited a follow-up clinic at one of four hospitals. All members had a full-scale IQ score of 80 or higher. Perinatal information was obtained retrospectively from medical records. Each subject underwent four reading tasks, testing monomoratic syllable reading, word reading, non-word reading and short sentence reading. Subjects with an SD reading time score greater than 2.0 in two or more tasks were considered to have reading difficulty (RD). Furthermore we investigated the relations between RD and perinatal factors using logistic regression analysis adjusted for potential confounding factors.

Results: Twenty-five (31.6%) out of 79 subjects had RD. We discovered that treated retinopathy of prematurity (tRoP) was a significant risk factor (adjusted OR=5.80, 95% confidence interval=1.51-22.33).

Conclusion: The rate of RD in school-aged VLBWI was higher than the estimated prevalence of dyslexia in Japan. Even in children with normal intelligence, long-term developmental follow-up including support for reading skills is necessary for VLBWI. Further investigation is desired to elucidate the relations between visual problems and RD in school-aged children.