Mathewson K J, Saigal S, Van Lieshout R J, Schmidt L A
Child Emotion Lab, Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON, Canada.
Department of Pediatrics, McMaster University, Hamilton, ON, Canada.
J Intellect Disabil Res. 2023 Mar;67(3):186-204. doi: 10.1111/jir.13021.
Infants born at extremely low birthweight (ELBW: ≤1000 g) are vulnerable to intellectual disabilities, but the factors that may distinguish between ELBW survivors with and without these impairments are not well understood. In this study, prospective associations between neonatal factors and functional outcomes in childhood and adolescence were compared in ELBW survivors with and without borderline intellectual functioning (BIF).
Borderline intellectual functioning was defined by IQ < 85, assessed at 8 years. Among 146 ELBW survivors, 48 (33%) had IQ scores under 85, and 98 (67%) had scores equal to or over 85. Group differences in demographic and risk factors were assessed via t-test, chi-squared analysis or non-parametric tests. Neonatal factors that differed between ELBW groups were tested for association with adaptive behaviour assessed at age 5 years, and reading and arithmetic skills assessed at ages 8 and 15 years, using hierarchical regression models.
Extremely low birthweight survivors with BIF had significantly lower birthweights than ELBW survivors without BIF (790 vs. 855 g, P < 0.01) and were more likely to be born to mothers with lower socioeconomic status (SES) (78% vs. 48%, P < 0.01). These ELBW survivors also were more likely to be diagnosed with significant neurosensory impairment (NSI; 35% vs. 19%, P < 0.04), experienced more bronchopulmonary dysplasia (56% vs. 38%, P < 0.04), received more days of respiratory support (median 33 vs. 14 days, P < 0.01) and remained in hospital for longer periods (median 81 vs. 63 days, P < 0.03). Birthweight, familial SES, NSI and duration of respiratory support were significant predictors for one or more outcomes. Across groups, lower familial SES was associated with lower academic scores (Ps < 0.05), and NSI predicted lower adaptive functioning (Ps < 0.001). Other associations were moderated by group: among ELBW survivors with BIF, heavier birthweights predicted better arithmetic skills, the presence of NSI was associated with poorer arithmetic skills and more ventilation days predicted poorer reading skills.
At birth, ELBW survivors with BIF faced more physiological and social disadvantages and required more medical intervention than their ELBW peers without BIF. Smaller birth size, NSI burden and prolonged neonatal ventilatory support displayed gradients of risk for childhood and adolescent academic outcomes across groups. Whereas academic performance in ELBW survivors with BIF was sensitive to variation in birth size, NSI or ventilation days, ELBW survivors without BIF attained thresholds of intellectual ability that were sufficient to support higher levels of academic performance at both ages, regardless of their status on these factors. The findings are discussed in relation to Zigler's developmental theory of intellectual disability.
极低出生体重（ELBW：≤1000克）的婴儿易患智力残疾，但对于区分有无这些损伤的ELBW存活者的因素，人们了解并不充分。在本研究中，比较了有边缘智力功能（BIF）和无边缘智力功能的ELBW存活者中，新生儿因素与儿童期和青春期功能结局之间的前瞻性关联。
边缘智力功能定义为8岁时智商<85。在146名ELBW存活者中，48名（33%）智商得分低于85，98名（67%）得分等于或高于85。通过t检验、卡方分析或非参数检验评估人口统计学和风险因素的组间差异。使用分层回归模型，对ELBW组间存在差异的新生儿因素与5岁时评估的适应性行为、8岁和15岁时评估的阅读及算术技能进行关联检验。
有BIF的极低出生体重存活者出生体重显著低于无BIF的ELBW存活者（790克对855克，P<0.01），且其母亲社会经济地位（SES）较低的可能性更大（78%对48%，P<0.01）。这些ELBW存活者也更可能被诊断为有严重神经感觉损伤（NSI；35%对19%，P<0.04），患支气管肺发育不良的情况更多（56%对38%，P<0.04），接受呼吸支持的天数更多（中位数33天对14天，P<0.01），住院时间更长（中位数81天对63天，P<0.03）。出生体重、家庭SES、NSI和呼吸支持时长是一个或多个结局的显著预测因素。在所有组中，较低的家庭SES与较低的学业成绩相关（P<0.05），且NSI预示着较低的适应性功能（P<0.001）。其他关联因组而异：在有BIF的ELBW存活者中，出生体重较重预示着算术技能更好，存在NSI与较差的算术技能相关，呼吸支持天数更多预示着阅读技能较差。
出生时，有BIF的ELBW存活者比没有BIF的ELBW同龄人面临更多生理和社会劣势，需要更多医疗干预。较小的出生体型、NSI负担和延长的新生儿通气支持在各组中均显示出儿童期和青春期学业结局的风险梯度。虽然有BIF的ELBW存活者的学业表现对出生体型、NSI或通气天数的变化敏感，但没有BIF的ELBW存活者达到了智力能力阈值，足以在两个年龄段都支持较高水平的学业表现，无论他们在这些因素上的状况如何。结合齐格勒的智力残疾发展理论对这些发现进行了讨论。
