Interleukin-6 polymorphism and bronchopulmonary dysplasia risk in very low-birthweight infants


Touhei Usuda, PhD, Division of Pediatrics, University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan. Email:


Background:  The aim of the present study was to evaluate the role of interleukin (IL)-6-634 polymorphism in neonatal disorders such as bronchopulmonary dysplasia (BPD) and periventricular leukomalacia (PVL) in very low-birthweight (VLBW) infants.

Methods:  This prospective cohort study included 202 infants (gestational age at birth, 23–34 weeks; birthweight, 500–1499 g). Genotypic analysis (polymerase chain reaction–restriction fragment length polymorphism) was performed with DNA extracted from whole-blood samples.

Results:  Genotype distribution (66.8% CC, 28.2% CG, 5.0% GG) was similar to that in the adult Japanese population. BPD occurred in 85 infants (42.1%) among 202 VLBW infants. The duration of O2 therapy in infants with CG/GG genotypes was significantly longer than that in infants with the CC genotype (CG/GG vs CC: 40.3 ± 52.2 days vs 28.4 ± 32.6 days, P < 0.05), but the prevalence of BPD was not associated with the CG/GG genotype (CG/GG, 40.0%; CC, 46.3%, P= 0.24). Infants with CG/GG genotypes were more likely to have received postnatal corticosteroid therapy for BPD than those with the CC genotype (CG/GG vs CC: 20.9% vs 11.1%, P= 0.05). PVL occurred in six infants (3.0%). There was no significant difference in the prevalence of PVL among IL-6-634 polymorphisms (CG/GG, 3.0%; CC, 3.0%, P= 0.65).

Conclusions:  IL-6-634 polymorphism is associated with duration of oxygen therapy in VLBW infants. This suggests that the IL-6-634 polymorphism G allele is an aggravating factor of BPD. IL-6-634 polymorphism is not associated with PVL.