Couples' nighttime sleep efficiency and concordance: evidence for bidirectional associations with daytime relationship functioning.

OBJECTIVE: To examine prospectively the directionality of the association between daily relationship functioning and nightly sleep quality and the association between couples' relationship functioning and concordance in sleep-wake rhythms. Emerging evidence suggests the existence of bidirectional links between sleep and relational processes in dyads, but to date, this research has been primarily cross sectional.

METHODS: Sleep was measured via both diaries and wrist actigraphy for 7 days in 29 heterosexual cosleeping couples. Ecological momentary assessment methods were used to characterize daily relationship functioning. Dyadic, multilevel analyses were used to examine the degree to which nightly sleep efficiency or within-couple concordance in sleep timing predicted the next day's relational functioning and vice versa.

RESULTS: In the first set of analyses, for men, higher diary-based sleep efficiency predicted less negative partner interaction the following day. For women, less negative partner interaction during the day predicted greater actigraphy-based sleep efficiency that night. Furthermore, if women reported more positive and less negative daytime partner interaction during the day, this also predicted higher diary-based sleep efficiency for their male partners that night. In the second set of analyses, among females only, lower diary- or actigraphy-based sleep onset concordance respectively predicted less positive and more negative partner interactions the next day.

CONCLUSIONS: Bidirectional associations seem to exist between sleep parameters and interpersonal interaction and may represent a novel pathway linking close relationships with physical and mental health.