Long-term cognitive outcomes of prematurely born infants: A longitudinal follow-up of Denver II, Bayley III and WISC-IV Tests

Background Prematurity constitutes a risk factor for developmental delay in infancy and childhood. This study aims to: (i) determine long-term cognitive outcomes in prematurely delivered children and compare them with term-delivered children using the WISC-IV and Stroop tests; (ii) examine the relation between Denver II, Bayley III and WISC-IV, Stroop tests. Methods The study group consisted of children born prematurely who had been tested with Denver II and Bayley III in their first 2 years, and had been evaluated with WISC-IV and Stroop tests under follow up, 6-10 years later. Results The study group (n = 60, 25 F, 35 M) was 8.0 +/- 2.4 (6-10.7) years old when given WISC-IV and Stroop tests. Gestational age in the study group was 34-37 weeks in 25%, 30-33 weeks in 48.3%, and <29 weeks in 26.7%. On WISC-IV, the verbal comprehension index, perceptual reasoning index, working memory index, and full-scale IQ scores were lower in the study group than the control group (P < 0.05). The study group took longer to complete the Stroop test (P < 0.05). Lower socioeconomic status (P = 0.005) and parental education level (P = 0.000) were associated with lower verbal comprehension index scores. Denver II and Bayley III test results were related to WISC-IV results (P < 0.05) but not to the Stroop test results (P > 0.05). Conclusions Our results showed prematurity negatively influences the results of WISC-IV and Stroop tests at school age. Denver II and Bayley III tests applied at age 2 years likely predict WISC-IV results.