Background Phototherapy is used on the majority of preterm infants with unconjugated hyperbilirubinaemia. The use of fluorescent tube phototherapy is known to induce oxidative DNA damage in infants and has largely been replaced by blue light-emitting diode phototherapy (BLP). To date, it is unknown whether BLP also induces oxidative DNA damage in preterm infants.

Objective To determine whether BLP in preterm infants induces oxidative DNA damage as indicated by 8-hydroxy-2′deoxyguanosine (8-OHdG).

Design Observational cohort study.

Methods Urine samples (n=481) were collected in a cohort of 40 preterm infants (24–32 weeks’ gestational age) during the first week after birth. Urine was analysed for the oxidative marker of DNA damage 8-OHdG and for creatinine, and the 8-OHdG/creatinine ratio was calculated. Durations of phototherapy and levels of irradiance were monitored as well as total serum bilirubin concentrations.

Results BLP did not alter urinary 8-OHdG/creatinine ratios (B=0.2, 95% CI −6.2 to 6.6) at either low (10–30 µW/cm²/nm) or high (>30 µW/cm²/nm) irradiance: (B=2.3, 95% CI −5.7 to 10.2 and B=−3.0, 95% CI −11.7 to 5.6, respectively). Also, the 8-OHdG/creatinine ratios were independent on phototherapy duration (B=−0.1, 95% CI −0.3 to 0.1).

Conclusions BLP at irradiances up to 35 µW/cm²/nm given to preterm infants ≤32 weeks’ gestation does not affect 8-OHdG, an oxidative marker of DNA damage.