Cosleeping in context: sleep practices and problems in young children in Japan and the United States.

OBJECTIVE To determine the relationship between cosleeping and sleep problems in cultures with very different sleep practices. DESIGN Interview study. SETTING Families in urban Japan and the United States identified through pediatric and other professional contacts. PARTICIPANTS Parents of healthy 6- to 48-month-old children (56 Japanese parents and 61 white US parents). All children had been breast-fed and lived in 2-parent, middleclass households. INTERVENTION None. MAIN OUTCOME MEASURE Sleep practices and sleep problems. RESULTS More Japanese than US children coslept 3 or more times per week (59% vs. 15%, P<.001). All cosleeping Japanese children regularly slept all night with their parents (vs. 11% of US cosleepers, P<.001). Japanese and US children did not differ in part-night cosleeping (7% vs. 13%, P = .37). Most Japanese children had adult company and body contact as they fell asleep, and fathers slept separately in 23% of families. A greater proportion of US children had regular bedtime struggles and night waking. Within the US sample, cosleeping was associated with more bedtime struggles (P<.001), night waking (P<.01), and overall stressful sleep problems (P<.01). In the Japanese sample, cosleeping was associated only with night waking (P<.05); however, the proportion of cosleeping Japanese children with frequent night waking was at the level reported for US children who slept alone (30% vs 23%, P = .47). CONCLUSIONS Cultural differences seem to influence the relationship between sleep practices and sleep problems. The experience of the Japanese families indicates that cosleeping per se is not associated with increased sleep problems in early childhood.