Cognitive and neuropsychological impairment associated with extremely preterm (EP) birth persists into young adulthood, according to findings from the 1995 EPICure cohort.
Of note, intellectual impairment increased significantly after the age of 11 years among 19-year-olds in the cohort of individuals born EP, Helen O’Reilly, PhD, of the Institute for Women’s Health at University College London and colleagues reported in.
Neuropsychological assessment to examine general cognitive abilities, visuomotor abilities, prospective memory, and certain aspects of executive functioning and language in 127 cases and 64 term-born controls showed significantly lower scores across all tests in those born EP.
Impairment in at least one neuropsychological domain was present in 60% of EP birth cases (compared with 21% of controls), with 35% having impairment in at least four domains. Most deficits occurred in general cognitive function and/or visuomotor abilities.
Further,and those with cognitive impairment at 11 years were at increased risk of deficit at 19 years (RR, 3.56), even after adjustment for sex and socioeconomic status, the authors wrote.
None of the term-born controls had a cognitive impairment at 11 years, and two (3%) had impairment at 19 years.
Studies of adults born very preterm have revealed that these individuals are at risk for neuropsychological impairment, but the extent of such impairment in individuals with EP birth, defined as birth before 26 weeks’ gestation, had not previously been studied in the long term.
Assessments in the EPICure cohort of individuals born EP in 1995 previously showed scores at 1.1-1.6 standard deviations lower on measures of general cognitive function, compared with standardized norms and/or term-born controls, at age 2.5, 6, and 11 years, Dr. O’Reilly and colleagues explained.
The current findings indicate that general cognitive and neuropsychological functioning problems associated with EP birth persist and can increase into early adulthood, and they “highlight the need for early and ongoing neuropsychological and educational assessment in EP children to ensure these children receive appropriate support in school and for planned educational pathways,” the investigators concluded.
In an accompanying, Louis A. Schmidt, PhD, and Saroj Saigal, MD, of McMaster University, Hamilton, Ont., wrote that these findings “provide compelling evidence for persistent effects of cognitive impairments” in individuals born EP.
They highlighted three lessons from the study:
- It is important to control for anxiety in future studies like this “to eliminate potential confounding influences of anxiety when examining performance-based measures in the laboratory setting,” as individuals born EP are known to exhibit anxiety.
- Group heterogeneity also should be considered, as all survivors of prematurity are not alike.
- Measurement equivalency should be established between groups.
With respect to the latter, “although many of the measures used by O’Reilly et al. have been normed, issues of measurement invariance have not been established between EP and control groups on some of the measures reported,” Dr. Schmidt and Dr. Saigal wrote, noting that “many other studies [also] fail to consider this fundamental measurement property.”
“Considering issues of measurement equivalency is of critical importance to ensuring unbiased interpretations of findings,” they added, concluding that the findings by O’Reilly et al. represent an important contribution and confirm findings from many prior studies of extreme prematurity, which “informs how we effectively manage these problems.”
“As the percentage of preterm birth continues to rise worldwide, coupled with reduced morbidity and mortality, and with more EP infants reaching adulthood, there is a need for prospective, long-term outcome studies of extreme prematurity,” Dr. Schmidt and Dr. Saigal added.
The study was funded by the Medical Research Council United Kingdom. The authors reported having no relevant financial disclosures. The editorial by Dr. Schmidt and Dr. Saigal, who also reported having no relevant financial disclosures, was supported by the Canadian Institutes of Health Research.
SOURCES: O’Reilly H et al. ; Schmidt LA, Saigal S. .