BackgroundPhototherapy 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 The use of fluorescent tube phototherapy is known to induce oxidative DNA damage in infants and has largely been replaced by blue light-emitting diode phototherapy (BLP).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.ObjectiveTo determine whether BLP in preterm infants induces oxidative DNA damage as indicated by 8-hydroxy-2′deoxyguanosine (8-OHdG).DesignObservational cohort study.MethodsUrine 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.ResultsBLP 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).ConclusionsBLP 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.