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Persisting cognitive deficits in survivors of very low birthweight and their implications for adult functioning

Survival rates among very-low-birthweight (VLBW, <1500g) infants increased dramatically during the 1980s and 1990s, especially among those born with more extreme preterm birth. The survivors are now entering young adulthood and are facing challenges not encountered in their school-age years. They are enrolled in post-secondary education or vocational training programs, or are working or seeking employment. With varying degrees of success, they are also gaining independence from their parents in decision-making and selfcare, and are establishing adult relationships or even beginning families of their own. Review of outcomes of VLBW in young adulthood suggests that many survivors may encounter more problems in facing these challenges than their term-born, normal birthweight peers. As a group, young adults with VLBW perform less well on tests of cognition and achievement than age-matched controls. Despite inconsistencies across studies, they also may be prone to inattention and internalizing symptoms. Studies examining functional outcomes in young adults with VLBW confirm lower or delayed educational attainment and difficulties in establishing social relationships. A Norwegian national study of adult outcomes found that lower gestational age predicted lower income and a decreased likelihood of finding a life partner and having children, suggesting functional limitations for that portion of the VLBW population with more extreme prematurity. Outcomes are nevertheless highly variable and many if not most VLBW survivors appear to lead normal adult lives. Long-term follow-up studies such as that by Løhaugen et al. provide information that is useful in identifying affected individuals with VLBW and in characterizing their cognitive deficits. A major strength of the study is the administration of the full form of the Wechsler Intelligence Test, which provides a broader and more reliable index of global cognitive ability. Use of the full form also sheds new light on the magnitude of group differences across subtests and ability indices. The observation of pronounced weaknesses on the Wechsler Adult Intelligence Scale Perceptual Organization Index in the VLBW group compared with controls is consistent with previous literature. However, the fact that there were group differences on all ability indices and on multiple verbal as well as performance subtests suggests that cognitive impairment in early adulthood is more pervasive than suggested by past studies using shortened versions of IQ testing batteries. Another important finding is the much higher rate of low IQ scores (>1SD below the mean of the controls) in the VLBW group, indicating that reduced IQ is a relatively common finding among survivors. A higher rate of participation in vocational programs in the VLBW group also adds to other evidence for effects of VLBW on employment. More research is needed to better understand factors related to variability in cognitive outcomes of VLBW, the pattern of cognitive strengths and weaknesses evident in adulthood, and the relation of cognitive skills to functional adaptations. Although Løhaugen et al. did not find that neonatal risk factors were related to IQ scores when individuals with cerebral palsy were excluded from analysis, past studies have documented associations of cognitive deficits with more extreme low birthweight, intrauterine growth retardation, and longer periods of oxygen treatment. Assessment of VLBW-related brain abnormalities and environmental characteristics has the potential to yield more accurate predictions of individual outcomes. Measures of executive function and other skills frequently impaired in survivors of VLBW (but not comprehensively probed by IQ tests) will also be useful in clarifying the cognitive implications of variations in brain status and environmental-genetic background. Finally, little is known about the longer-term development of adults with VLBW or the relevance of cognitive weaknesses to problems in mental health, job performance, interpersonal and family relationships, and independent living skills. Although cognitive weaknesses may increase an individual’s vulnerability to these problems, outcomes are also dependent