Young children with irregular bed-times suffer intellectually, according to research published today.
A long-term study by researchers at the Department of Epidemiology and Public Health, University College London, UK, found that parents should aim to impose regular bedtimes, particularly at the age of 3, as this was an important time for cognitive development.
Going to bed at different times could have a knock-on effect on their health during their lives, they warn.
Authors Yvonne Kelly, John Kelly and Amanda Sacker have made the assertions after their study in which they looked to see if the time a child went to bed and the consistency of bed-times had any impact on intellectual performance.
They examined data from more than 11,000 seven year olds, all of whom were part of the UK Millennium Cohort Study (MCS), which used regular surveys and home visits when the children were 3, 5, and 7, to find out about family routines, including bedtimes.
The results, which were measured by validated test scores for reading, maths, and spatial awareness, are published in the latest edition of The Journal of Epidemiology and Community Health.
The authors found that irregular bedtimes were most common among 3-year-olds, when about 1 in 5 youngsters went to bed at varying times, but by the age of 7, more than half the children went to bed regularly between 7.30-8.30pm.
The authors found that children from more socially disadvantage backgrounds tended to have irregular bedtimes or who went to bed after 9 pm.
Seven-year-old girls tended to have lower scores on the three assessments if they had irregular bedtimes compared with children who had regular bedtimes. However, this was not the case among 7-year-old boys.
The authors found that irregular bedtimes by the age of 5 were not linked with poorer brain power in girls or boys at the age of 7.
However, haphazard bedtimes at the age of three were associated with lower scores in reading, maths, and spatial awareness in both boys and girls. The authors believe that this could be a sensitive period for cognitive development.
The impact of irregular bedtimes also seemed to be cumulative, they said.
Girls who never went to bed at the same time each night at ages 3, 5, and 7 had significantly lower reading, maths and spatial awareness scores than girls who had had consistent bedtimes. The impact was the same in boys, but for any two of the three time points.
The authors say that irregular bedtimes could disrupt natural body rhythms and cause sleep deprivation. This undermines the plasticity of the brain and the ability to acquire and retain information.
“Sleep is the price we pay for plasticity on the prior day and the investment needed to allow learning fresh the next day,” they write.
“Early child development has profound influences on health and wellbeing across the life course. Therefore, reduced or disrupted sleep, especially if it occurs at key times in development, could have important impacts on health throughout life.”
Kelly Y, Kelly J, Sacker A. Time for bed: associations with cognitive performance in 7-year old children: a longitudinal population-based study. J Epidemiol Community Health. 2013;0:1–6. doi:10.1136/jech-2012-202024 [abstract]
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