To determine the influence of breast-feeding on the prevalence and persistence of sleeping problems in southern Finland (SF) and southern Germany (SG).
Prospective binational population study of infants admitted to special care units (SCUs) in geographically defined areas in SF and SG.
In SF, the number of SCU infants was 1057 (very preterm, 47; preterm, 258; term, 752); 485 term infants were control subjects. In SG, the number of SCU infants was 4427 (very preterm, 284; preterm, 1419; term, 2724).
Parent reports of child sleeping problems at 5, 20, and 56 months of age.
Night waking at 5 months of age was less frequent for SCU very preterm (25.5%), preterm (40.6%), and term infants (48%) than for term control subjects (56.7% to 59.9%) in SF. No differences in sleeping behavior according to gestation were found at 20 and 56 months. Sleeping problems were greater in SF infants (25.5% to 48%) than in SG infants (15.1% to 19.1%) at 5 months of age and were explained by a higher rate of breast-feeding in SF. Breast-feeding had no long-term effects on night waking or on co-sleeping in SF. In contrast, breast-fed infants continued to wake more often in SG.
Breast-feeding rather than gestational age is strongly related to night waking. More support for dealing with night waking might prevent early termination of breast-feeding.