Adult IQ for Very Preterm and Very Low Birth Weight Babies Can Be Predicted by Age Two, Study Finds
Research from the University of Warwick shows that the adult IQ of individuals born very preterm or with very low birth weight can be reasonably predicted as early as age two.
The prospective study was led by Professor Dieter Wolke of the University of Warwick’s Department of Psychology and Warwick Medical School. It followed a birth cohort from southern Bavaria, Germany, known as the Bavarian Longitudinal Study, tracking cognitive development from infancy into adulthood.
Previous research has established a link between very preterm birth or very low birth weight and reduced cognitive performance throughout childhood and into adult life. What this study adds is a clearer timeline for when adult-level cognitive outcomes can be anticipated in these high-risk children.
Professor Wolke explained that this is among the first studies to examine the predictability of adult IQ in individuals over age 26 who were born very preterm (before 32 weeks gestation) or with very low birth weight (less than 1.5 kg). The research indicates that, for this group, cognitive assessments at around two years of age provide a fair prediction of adult IQ.
In contrast, the study found that children born at term generally do not yield reliable predictions of adult IQ until about age six. Across all measurement points, the very preterm and very low birth weight group scored lower on IQ tests than the term-born control group, even after excluding individuals with severe cognitive impairment from the comparisons.
The cohort included 260 infants born very preterm or with very low birth weight and 229 term-born controls. Cognitive function was assessed repeatedly using age-appropriate developmental and intelligence measures at 5 and 20 months, and at 4, 6, 8, and 26 years. The comparisons were not driven by sex, family income, or parental education, and control participants were recruited from the same obstetric wards.
Study findings highlighted two important points. First, children born very preterm or with very low birth weight face a higher risk of persistent cognitive problems that extend into adulthood. Second, cognitive outcomes for this group are relatively stable from an early age, with measurable differences apparent by 20 months. For clinicians and educators, this stability suggests that assessments at age two can help identify children who would benefit from early, targeted interventions.
Professor Wolke noted that while some very preterm or very low birth weight children show low test scores early on but improve over time, many with persistent difficulties are identifiable by their second year of life. Early detection creates an opportunity to plan specialised therapeutic, educational, and family support services that may improve longer-term outcomes.
Professor Wolke is based at the University of Warwick’s Department of Psychology and at Warwick Medical School. The university’s research programs include epidemiology, trials of complex interventions at individual, family and community levels, and investigation of social, cultural and environmental influences on mental health and wellbeing.
Source: Nicola Jones – University of Warwick
Original research: Breeman LD, Jaekel J, Baumann N, Bartmann P, Wolke D. “Preterm Cognitive Function Into Adulthood.” Pediatrics. Published online August 10, 2015. doi:10.1542/peds.2015-0608
Abstract
Preterm Cognitive Function Into Adulthood
Background: Very preterm (VP; gestational age <32 weeks) and very low birth weight (VLBW; <1500 g) births are associated with impaired cognitive function across the lifespan. It is unclear how stable cognitive function is from childhood into adulthood for VP/VLBW individuals compared with term-born peers, and how early adult cognitive function can be predicted.
Methods: The Bavarian Longitudinal Study followed 260 VP/VLBW and 229 term-born individuals from birth to adulthood. Cognitive function was assessed with developmental and IQ tests at 5 and 20 months and at 4, 6, 8, and 26 years.
Results: Across assessments, VP/VLBW participants had significantly lower IQ scores than term-born controls, even when excluding those with severe cognitive impairment. IQ scores were more stable over time for VP/VLBW individuals; however, differences in stability diminished when participants with cognitive impairment were excluded. Adult IQ could be predicted with fair certainty (correlation r > 0.50) from age 20 months onward for the VP/VLBW sample and from age six onward for term-born individuals.
Conclusions: VP/VLBW individuals are at increased risk of cognitive problems that often persist from early childhood into adulthood. These problems can be reliably identified by age two, supporting the recommendation for cognitive follow-up at 24 months to plan timely special support services.