Background: Chronotype is a construct contributing to individual differences in sleep-wake timing. Previous studies with children have found that evening-types exhibit greater sleep difficulties. Infant sleep quality can be modulated by several factors, such as parental characteristics. We examined the association between parental circadian preference and sleep in early childhood.

Methods: This study was based on a longitudinal birth cohort, with several measurement points. We used information regarding parental questionnaires during pregnancy and children's sleep measures at three, eight, 18 and 24 months. In total, 1220 mothers, 1116 fathers, 993 infants at three months, 990 infants at eight months, 958 children at 18 months, and 777 children at 24 months were analyzed. Parental circadian preference was measured using the Horne-Östberg Morningness-Eveningness Questionnaire. Concerning children's sleep, we used the Brief Infant Sleep Questionnaire (BISQ) and the Infant Sleep Questionnaire (ISQ) at each time point.

Results: Maternal circadian preference was associated with infants' circadian rhythm development at three, eight, 18 and 24 months. Furthermore, increased maternal eveningness was also related to short sleep during daytime at three months, and nighttime at three and eight months, to long sleep-onset latency at three, 18 and 24 months, to late bedtime at three, eight and 18 months, and to sleep difficulties at eight and 24 months. Paternal circadian preference was not associated with any sleep variable at any time point.

Conclusion: Maternal circadian preference is related to several sleep difficulties in early childhood, and it may be considered a potential risk factor for the onset of early sleeping problems.