Summary
Background: The mutual dependencies between mother and infant circadian rhythms are important
for examining disturbances of maternal circadian rhythms, which are considered substantial
risk factors for the development of maternal depression during childrearing periods.
Objectives: We characterized the mutual dependencies of maternal–infant circadian rhythms by
an index of synchronization properties and then tested the hypothesis that such an
index, specifically the instantaneous phase differences between their rhythms, is
associated with maternal mental health.
Methods: We performed longitudinal recordings of maternal symptoms of fatigue, stress, and
mood states by ecological momentary assessment, together with simultaneous measurements
of mother and infant physical activity data in daily life, on 20 mother–infant pairs
for a period of >1 week. The circadian components in their physical activity data
were extracted by ensembled bivariate empirical mode decomposition, and the corresponding
instantaneous phases were then obtained based on the Hilbert transformation. The associations
between diurnal maternal symptoms and absolute phase differences between mother and
infant circadian rhythms were tested by multilevel models.
Results: Diurnal fatigue and depressive mood scores showed positive and significant correlations
(p < 0.05) with the increase in instantaneous mother–infant phase differences, indicating
the significant role of synchronization of mother–infant circadian rhythms for maintaining
maternal mental health.
Conclusions: These findings suggest that modifications of maternal and/or infant circadian rhythms
may lead to the improvement of maternal mental health during child-rearing periods.
Keywords
Circadian rhythm - ecological momentary assessment - maternal mental health - physical
activity - empirical mode decomposition