UBC Theses and Dissertations
The effect of neurodevelopmental impairment definition on incidence rates among very preterm infants Haslam, Matthew David
Background: Various criteria are used to define severe neurodevelopmental impairment (SNI) and the effect of definition is rarely reported. Objective: To examine the impact of changes in SNI definition on incidence rates of SNI and the association between risk factors and SNI. Methods: We included infants (n=2187) born <29 weeks gestation between April 2009 and September 2011, who were admitted to a Canadian Neonatal Network Neonatal Intensive Care Unit (NICU) and assessed at 18-21 months corrected age by the Canadian Neonatal Follow-Up Network (CNFUN). Incidence rates of SNI were calculated for 7 commonly used definitions identified in the literature. Logistic regression was performed to identify risk factors for SNI using the definitions which yielded the highest and the lowest incidence rate of SNI. Adjusted odds ratios (AOR) and 95% confidence intervals (CI) were estimated for risk factors significantly associated with SNI. Results: SNI definitions were composed of six common criteria: cerebral palsy severity using the Gross Motor Function Classification System (GMFCS), motor, language, and cognitive Bayley-III scores, and visual or hearing impairment. SNI incidence ranged from 3.5% to 14.9% (highest vs lowest rate ratio 4.29; 95% CI: 3.37, 5.47). The definition yielding the highest incidence included at least one of: GMFCS score 3-5, Bayley-III motor, language, or cognitive score <70, bilateral visual impairment, or use of hearing aids or cochlear implants. The definition yielding the lowest incidence included at least one of: GMFCS score 4-5, Bayley-III language or cognitive score <55, or bilateral visual impairment. The associations between risk factors and SNI varied depending on the SNI definition used. Maternal ethnicity, employment status, antenatal steroid treatment, and gestational age at birth were inconsistent in the significance of their associations with SNI. Maternal drug use, infant male sex, score of neonatal acute physiology >20, late onset sepsis, bronchopulmonary dysplasia, and intraventricular hemorrhage were consistently associated with SNI, irrespective of the SNI definition used, although the strength of these associations varied. Conclusions: Criteria used to define SNI significantly influence SNI incidence and the associations between risk factors and SNI. A standardized definition of SNI would facilitate scientific communication and spatio-temporal comparisons.
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