Published in the Journal of Epidemiology and Community Health, the new study looked at bedtimes and standardized test scores of children who were part of the UK Millennium Cohort Study, a nationally representative study of children from the United Kingdom that followed children during ages 3, 5 and 7. In addition to gathering information about bedtimes and standardized tests in math, reading and spatial abilities at the age of 7, researchers controlled for specific socioeconomic factors and factors relating to discipline, breakfast routines and whether or not the parents read to the children. Home studies and regular surveys were also done to help monitor all changes over the course of the study.
What’s interesting about this study was that the researchers expected that late bedtimes would lead to poor cognitive test performance. Yet, as they looked at the data, it became apparent that the time wasn’t as important as the consistency of the child’s bedtime routine. This was true, even after accounting for various socioeconomic factors.
In both boys and girls, irregular betimes at age 3 were associated with lower test scores, but not at age 5. Bedtimes that had never been consistent for girls at ages 3, 5, and 7 were associated with lower test scores when compared to those with regular bedtimes, and for any two of these age groups, boys also displayed poorer test scores if they did not have a consistent sleep routine.
Though they’re not really sure why, girls seemed to show the most sensitivity to bedtime routines than boys. Sacker and her colleagues theorized that “it might be that girls are more susceptible to elements of the psychosocial environment than boys, and hence also more perturbed by inconsistent bedtime schedules.”
But essentially, for both boys and girls, the results “showed that it wasn’t going to bed late that was affecting child’s development, it was the irregular bedtimes that were linked to poorer developmental scores,” Amanda Sacker, professor in the Department of Epidemiology and Public Health at University College London told CNN Health. “If the child prefers to go to sleep a little bit later, but it’s done regularly, that’s still OK for them, according to the evidence.”
There are, of course, some limitations to this study. For example, even though a large group of participants was looked at, there was only a correlation between bedtime schedules; there’s no cause and effect here. So researchers can’t really say that irregular sleep is a direct driver of lower test scores.
And though there are some clear indications that suggest a regular bedtime is important to better academic performance, there’s another important question: what exactly is a “regular” bedtime? Does the child need to go to bed at exactly the same time every night, or can the hour be fudged a little, like say 20 minutes or half an hour? The study doesn’t say.
Also, researchers did not ask about the amount of sleep children received. Though parents did say what time their children went to bed and whether or not there was a consistent bedtime routine (which was self-reported, also a possible flaw), they didn’t report what time their children woke up in the morning or if their children woke up at all throughout the night. Therefore, it would be difficult to say if the amount of sleep played a role in how the study’s results turned out.
In addition, there’s no real answer as to why an irregular bedtime would affect test scores. There are a few theories, however. For example, children with irregular bedtimes may not get enough quality sleep because their body’s natural circadian rhythms may be disrupted by inconsistent sleep schedules. This is supported by other studies that have suggested that even adults can reap better quality sleep time by keeping a consistent bedtime hour each night.
It is thought that, by giving our brains and bodies regular times to process stimuli from the day, we ensure that we have enough room for fresh learning the next day.
“It not only helps with what’s gone on the day before, but it also sets you in good state for the day to come,” Sacker said.
And given the fact that cognitive impairment and lack of concentration are two potential consequences of limited and disrupted sleep, it would only make sense that it’s important for us to do everything we can to promote healthy sleep habits and high quality sleep in our homes. This is important, not only for childhood development, but also long-term health for our children, and ourselves.
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