Stable incidence but regional differences in retinopathy of prematurity in Norway from 2009 to 2017

Abstract

Purpose: To explore the changes over time and regional differences in the incidence of retinopathy of prematurity (ROP) in a national cohort of infants born <28 weeks' gestational age (GA).

Methods: A population-based study of infants with GA <28 weeks in Norway from 2009 to 2017. Prospectively collected data on clinical variables and outcomes were obtained from the Norwegian Neonatal Network.

Results: Of 1499 live-born infants transferred to a neonatal intensive care unit, 1156 were discharged alive. Four-hundred and fifty-eight infants (39.6%) had ROP, 152 (13.1%) had severe ROP, and 110 (9.5%) were treated for ROP. Eleven hundred infants (95.2%) had complete data sets. In a model comprising region of primary care, GA [odds ratios (OR): 0.65; 95% CI: 0.55-0.77], growth velocity (OR: 1.10; 95% CI: 1.00-2.00), medically treated patent ductus arteriosus (OR: 1.80; 95% CI: 1.19-2.72), weeks of supplemental oxygen (OR: 1.07; 95% CI: 1.03 to 1.11) and region of primary care (OR: 4.95; 95% CI: 3.05-8.04 for the pair of regions with the highest estimated OR) were significantly associated with severe ROP. Additionally, institutional differences for severe ROP were found, with ORs from 0.41 (95% CI: 0.05-3.23) to 5.36 (95% CI: 3.05-9.43) using the largest institution as reference. Incidences were stable over time after adjusting for GA. A larger proportion was treated with anti-vascular endothelial growth factor after 2011.

Conclusions: The incidence of severe ROP was stable between 2009 and 2017 in Norway. Regional and institutional differences need to be explored in future studies.

Keywords: anti-VEGF; incidence; population-based study; regional differences; retinopathy of prematurity; risk factors.