A consistent bedtime for children displayed better control over emotions and behaviour while working with others or under stress, a new study has found.

Researchers, including those from The Pennsylvania State University, US, analysed sleep and behaviour data of 143 six-year-olds, mothers of whom were trained about responsive parenting in the first 2.5 years following birth.

The parenting style revolves around responding to a child's emotional and physical needs in a warm and consistent manner. One of the aspects of responsive parenting involves creating a supportive and predictable sleep environment, techniques for which include comforting babies by rocking or patting, among others.

Responsive parenting helped children develop bedtime routines and sleep behaviours in the first year after birth, according to a 2016 study, published in the journal Pediatrics, which too was conducted by researchers at The Pennsylvania State University.

The latest study, which is a long-term one, showed the continued benefits of regular sleep timing in children, the authors said.

"Findings support the importance of consistency in sleep timing and how this may play a greater role in children's behavioural and emotional outcomes than mean actigraphic sleep duration and quality (measured using wearable devices)," they wrote in the study published in the Journal of Developmental and Behavioural Pediatrics.

"Children who had consistent bedtimes were generally able to regulate their behaviour and emotions. On the other hand, children whose bedtimes and sleep times were all over the place showed more impulsivity and less control," lead researcher Adwoa Dadzie, a doctoral student in biobehavioural health, Pennsylvania State University, said.

For the study, the children wore a monitor on their wrist for seven days that measured night-time sleep and activity. Aspects such as time of falling asleep and waking up, along with sleep efficiency and duration were recorded, the researchers described.

The data was compared with the children's performance on a task designed to test their response to feeling frustrated, the team said.

Each child selected a toy that they wanted to play with from a large selection. The chosen toy was placed in a clear box and locked. The child was given a set of keys, none of which unlocked the box, the authors explained.

The team then observed the child for self-regulated behaviour, including self-talk and trying each key, and a lack of self-regulation -- which included throwing the keys without trying them all. After four minutes, the children were handed the correct key to the box and allowed to play with the toy.

Another task involved in the study was collaborative, which tested the children for their ability to cooperate.

The results showed that the more a child's bedtime changed each night, the worse they regulated their behaviour and emotions.

For example, a child whose bedtime varied by 20 minutes a night over the week of the study typically displayed more self-regulation than a child whose bedtime shifted by two hours across the week.

The children participants were a part of the university's Intervention Nurses Start Infants Growing on Healthy Trajectories (INSIGHT) study.

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