Preterm children with very low birthweight (VLBW) / extremely low birthweight (ELBW) with normal early development had been found poorer executive functions (EFs) at preschool-age (Ni, Huang & Guo, 2011). The previous study found that the risks of deficits in EFs at preschool-age of preterm children can be attenuated by more supportive home environment (Taylor & Clark, 2016). However, former studies didn't investigate the effect of birthweight and home environment on cognitive EFs of preterm children simultaneously, especially those with normal early development. The present study aims to investigate the predictive effect of birthweight and home environment on the cognitive EFs of VLBW / ELBW preterm children.

The preterm children were recruited from the Premature Baby Foundation of Taiwan. Inclusion criteria were their scores of Bayley Scales of Infant and Toddler Development, second or third edition at 12 and 24 months, and Wechsler Preschool and Primary Scale of Intelligence, Revised Edition at 5 years old were higher than 70. Exclusion criteria were visual impairment, hearing impairment, and cerebral palsy. There was a total of 287 preterm children with age 6 recruited in the present study. Preterm children were then divided into VLBW group (n=202, birthweight between 1001-1500g) and ELBW group (n=85, birthweight less than 1000g). The typical children included 89 term-born healthy and typically developing children with age 6, who were recruited from comparable social status families in the community. Four types of cognitive EFs including 22 indicators were assessed. Inhibition ability including 8 indicators was assessed through Comprehensive Nonverbal Attention Test Battery (CNAT), cognitive flexibility including 6 indicators was assessed through Wisconsin Card Sorting Test (WCST), working memory including 2 indicators was assessed through Digit Span Subtest of Wechsler Intelligence Scale for Children-IV (WISC-IV) and Knox's Cube Test (KCT), planning ability including 6 indicators was assessed through Tower of London (ToL). The home environment was assessed through Home Observation for Measurement of the Environment (HOME), Revised edition. Data were analyzed with Stepwise Regression.

Results showed that the regression model with birthweight significantly predicted 83.3% of planning ability indicators, 83.3% of cognitive flexibility indicators, and 50% of working memory indicators. Among indicators mentioned above, birthweight has been found the greatest predictive effect on summation-of score of ToL (R2=.04, p<.001). The regression model with HOME significantly predicted 66.7% of planning ability indicators, 16.7% of cognitive flexibility indicators, and 12.5% of inhibition ability indicators. Among the indicators mentioned above, HOME has been found the greatest predictive effect on rule-1 of ToL (R2=.027, p=.001). The regression model with birthweight and HOME significantly predicted 50% of planning ability indicators. Among indicators mentioned above, the regression model has been found the greatest predictive effect on summation-of-score of ToL (R2=.061, p<.001).

Both birthweight and home environment have been found significantly predicted different types of cognitive EFs at preschool-age of VLBW / ELBW preterm children with normal early development. Though the home environment doesn't have such a great predictive effect as birthweight is, both birthweight and home environment are significant predictors of planning ability.