pediatric housecalls Robert R. Jarrett M.D. M.B.A. FAAP

Bedtimes and Children’s Thinking Ability

August 14, 2013

In most of our practices, questions about children’s bedtimes are one of the most frequent queries from parents pediatricians receive. And, I thought we had just about covered it until I heard about some new research on: NO bedtimes — or better said, no specific time for bed.

Once I finish describing the study the reasons will sort of sound obvious to you but I have to confess I learned a couple of things that I hadn’t considered before about irregular bedtimes.

It seems that we now have evidence that irregular bed-times in early childhood may actually impair children’s cognitive development and even have damaging long-term health effects throughout life.

Frankly, I’ve had friends and acquaintances with children in both groups (regular and irregular); and, I have to say from mere casual observation, the ease of parenting and quality of life for parents is so much better when the kids have regular bed-times that I’m hard pressed to understand why a parent would want it any other way.

However, I’m sure that there was some explanation that some of them drifted into the irregularity. I’m just not sure that I now remember what it was, if ever I did know. If I had known these study results back then, I would have found a way to bring it up in conversation; but, I didn’t back then.

The Millennium Cohort Study

Back in 2000 a group of “Brits” began a massive undertaking that they called “The Millennium Cohort Study (MCS).” It is an extremely large scale effort where huge numbers of children born in the new millennium are studied over many years (thirteen so far) on everything from habits to health and development to diseases.

There are so many children included in the MCS that the group of investigators from University College in London had no problem including over 11,000 children born between September 2000 and January 2002 as a “cohort” to study bedtime rituals and cognitive development. They are now able to supersede a few previous, much smaller, studies that had “mixed” (conflicting) results.

We’ve known that sleep plays a key role in maintaining healthy brain and intellect function; but, till now, nearly all studies concern adults and adolescents and we’ve known almost nothing about its relation to the developing child’s brain.

The researchers simply analyzed bedtimes from age 9 months and 3, 5, and 7 years where home visits were conducted and questions about socioeconomic circumstances, demographic characteristics, family routines (including bedtimes) and psychosocial environment were asked.

On 7-year-old’s, cognitive assessments were done by trained interviewers to measure reading, mathematics, and spatial abilities. Then they controlled for socioeconomic status in addition to other factors such as discipline strategies, reading to children and breakfast routines.

Irregular Bedtimes Not Good For Kids

The findings were that: irregular bedtimes in toddlers are associated with lower cognitive test scores at age 7 years – and girls are particularly affected.

The fact that impairment at such a young age can definitely lead to life-long effects prompted the investigators to look deeper and expand on their findings. For example, are the effects cumulative and is any age-group more susceptible.

Keeping in mind the study was done in England with British parenting practices, here’s what we now know more fully about children’s bedtimes and their mental development:

• Irregular bedtimes are most common at age three where 20% had irregular bed times.
• At age 7 more than 50% went to bed between 7:30 and 8:30 pm.
• Irregular bedtimes at age 3 is associated with lower reading, mathematics and spatial scores in both boys and girls.
• For boys, irregular bedtimes at any 2 of the tested ages was linked to lower reading, mathematics, and spatial scores.
• At age 7, not having a regular bedtime was related to lower reading, mathematics, and spatial for girls; but not for boys – possibly related to statistical methods of correcting for parental habits (see below).
• In addition, for girls there was a substantial cumulative effect. Those who had never had regular bedtimes at ages 3, 5 and 7 had substantially impaired reading, math and spatial scores.
• Age three may be a particularly sensitive period for cognitive development.
• Going to bed later had less statistical effect than whether it was irregular.
• in general, children who had irregular bedtimes or went to bed after 9 p.m. tended to come from lower socioeconomic backgrounds than other study participants.

So, What Does This Mean?

Well, look. You know that sleep is where your brain “consolidates” all the memories that you accumulate during the day, right? It’s like living “real time” is a whole lot faster than the poor brain neurons are able to construct all the new pathways it takes to remember them; so, “real time” gets the pause button while the neurons catch up.

It’s just like all your streaming You Tube videos which need to be buffered by your computer once in awhile to let the “streaming” catch up with the video display.

Now days that’s called: “plasticity” – all the processes having to do with embedding new knowledge, memory and skill into the developing brain structure. “Sleep is the price we pay for plasticity” the scientists tell us. To us it means: “You have fun, you learn, you live … you sleep!”

Early child development has profound influences on health and well-being across the whole life course. Therefore, reduced or disrupted sleep, especially if it occurs at key times in development, could have critically important impacts on health throughout life.

The researchers speculate that inconsistent bedtimes might be causing the results that they found in possibly 2 ways: “First, causing a disruption of the normal circadian rhythm of sleep cycles; and/or, second, by causing sleep deprivation and its subsequent effect on brain plasticity.”

“Sleep is the price we pay for plasticity on the prior day and the investment needed to allow learning fresh the next day” they say; so, if you don’t get adequate amount or quality – you don’t learn or develop correctly.

The Rest of the Story

Even though these were excellent and hard-won statistics on a massive sample size, you realize that they are still just statistical relations not definitive causes, right? Even though a parent should be able to draw logical conclusions for their own parenting techniques, the study still hasn’t proven a cause and effect relationship, right?

Why are girls more affected than boys by inconsistent bedtimes? Possibly they’re more susceptible to the environment and more easily perturbed by inconsistent bedtime schedules.

In the midst of the study the researchers felt they needed to control for the variation in other aspects of parenting and social environment. In general children with irregular bedtimes or bedtimes after 9 p.m. came from lower socioeconomic backgrounds. They were more likely to be from lower income homes and have mothers with poorer mental health. They were also less likely to have breakfast and be read to daily.

Perhaps is was these statistical corrections which caused the statistics not to show as great for five year old boys; but, that needs more study. It also points out the difficulty in finding actual causes things like this and doing research on this kind of topic.

And, lastly, I wish the Millennium Study had a question about how much sleep the children were getting during the night and not just what time they went to bed.

If It Were Me

If it were me, I’d be putting them to bed at regular times from birth till they went away to college, if it took double-sided tape and super glue!

Oh, and parenthetically, there is even more scientific data which shows that a regular bedtime is better for adults than we have accumulated yet for children.

[Journal of Epidemiology and Community Health, July 8, 2013]