Mother–infant circadian rhythm: Development of individual patterns and dyadic synchrony.

Background Mutual circadian rhythm is an early and essential component in the development of maternal–infant physiological synchrony. Aims The aim of this to examine the longitudinal pattern of maternal–infant circadian rhythm and rhythm synchrony as measured by rhythm parameters. Study design In-home dyadic actigraphy monitoring at infant age 4, 8, and 12 weeks. Subjects Forty-three healthy mother–infant pairs. Outcome measures Circadian parameters derived from cosinor and non-parametric analysis including mesor, magnitude, acrophase, L5 and M10 midpoints (midpoint of lowest 5 and highest 10 h of activity), amplitude, interdaily stability (IS), and intradaily variability (IV). Results Mothers experienced early disruption of circadian rhythm, with re-establishment of rhythm over time. Significant time effects were noted in increasing maternal magnitude, amplitude, and IS and decreasing IV ( p < .001). Infants demonstrated a developmental trajectory of circadian pattern with significant time effects for increasing mesor, magnitude, amplitude, L5, IS, and IV ( p < .001). By 12 weeks, infant phase advancement was evidenced by mean acrophase and M10 midpoint occurring 60 and 43 min (respectively) earlier than at 4 weeks. While maternal acrophase remained consistent over time, infants became increasingly phase advanced relative to mother and mean infant acrophase at 12 weeks occurred 60 min before mother. Mother–infant synchrony was evidenced in increasing correspondence of acrophase at 12 weeks ( r = 0.704), L5 ( r = 0.453) and M10 ( r = 0.479) midpoints. Conclusions Development of mother–infant synchrony reflects shared elements of circadian rhythm. [ABSTRACT FROM AUTHOR]