Aims The influence of a 24 h light-dark rhythm in neonatal care on sleep and crying patterns of preterm infants was examined using standard diary measures over 3 consecutive days at corrected ages of 5 and 11 weeks.

Methods 41 preterm infants (<32 weeks gestational age) were either nursed in the standard 24 h dim light condition (control group; n = 21) or in a cycled condition (7am–7pm light, 7pm–7am dark; intervention group; n = 20). Variables for sleep, wake and content, fussing, crying and unsoothable crying were analysed in four 6 h intervals starting at midnight.

Results A preliminary analysis by repeated measure ANOVA including 29 preterm infants (15 controls, 14 intervention group) showed a significant interaction between interval and age for the variables sleep and awake and content (5 weeks: most sleep between 24:00–12:00; 11 weeks: between 18:00–6:00; opposite for awake and content). Fussing and crying showed an age (fussing: P<0.008, crying: P<0.029) and interval (fussing: P<0.00, crying: P<0.003) effect with more fussing at 5 weeks and in the evening hours. For fussing a significant interaction between age and intervention (P<0.024) was found with less fussing episodes at 5 weeks of age for infants nursed in cycled condition (0.26 hours vs 0.5 hours).

Summary and Conclusion While no differences in sleep, wake and content, crying and unsoothable crying were found between the two conditions, nursing in a cycled light condition reduced fussing episodes at the peak age of 5 weeks.