Regulatory Sleep Systems

Any links to Amazon are affiliate links.


In Healthy Sleep Habits, Happy Child, Weissbluth talks about two regulatory systems the body uses for sleep (pages 15-16). These are Homeostatic Control Mechanism (which I shall henceforth refer to as HCM) and Circadian Timing System or Internal Timing System (which I shall refer to as circadian rhythm because that is how I first learned it). The information in the book on these two topics is not extensive; it is only two paragraphs long. But there have been tons of studies on the two topics.

HCM basically is the body’s function for making up for lost sleep. The longer you are awake, the longer your body will try to sleep. Your body wants to restore lost sleep. Weissbluth says this is a system we cannot control, much like sweating. If we are hot, we will sweat.

My personal commentary on HCM. First of all, the term HCM isn’t a great one. There are lots of homeostatic control mechanisms. The human body is full of them. The liver, the kidneys, the brain…the brain is full of them :). Homeostasis is basically the body working to to keep things stable in the body despite external forces. If homeostasis fails, things like diabetes, dehydration, hypoglycemia, etc. can occur.

I think the way Weissbluth refers to HCM makes it sound like, “If your baby needs to sleep, he will. His body will make up for it. Plus, if he is awake for a long time, he will sleep for a long time.” Now, there is much throughout the book to negate that feeling, but his info on HCM definitely leads you in that direction.

And many parents come to this idea on their own. They keep baby awake longer in order to try to get longer naps or more nighttime sleep out of the baby. But we know sleep begets sleep, and creating an overly tired baby causes major sleep problems.

Here is a better way of looking at HCM in sleep. The HCM drives the body to sleep. As you are awake, you build up a need for sleep–a sleep debt. The longer you are awake, the more your body wants to sleep. So the HCM doesn’t mean you will definitely sleep when needed. It is a way for your body to tell you to sleep. But not all people, babies included, listen to this drive.

You can’t look at HCM by itself to figure out sleep needs. Some bodies are likely better at self-regulating need for sleep. They have better homeostatic control, just like some bodies are better at managing sugar than others. You also have to consider how long it has been since the person slept….optimal waketime. And we also have circadian rhythm to consider.

Whew! Feeling a bit of information overload? Take a deep breath. Get a drink.

Let’s keep going.

Aaahhh Circadian Rhythm. I find this very fascinating. To be quite honest, I really only wanted to write about circadian rhythm, but the two are pretty interdependent, so that is why we have talked about HCM.

The Circadian Rhythm is set to sunlight. It uses the sun to make sure the body is sleeping when it should and that you are having correct stages while sleeping. The circadian rhythm is about 24 hours (circadian is based on a Latin word that translates to “about a day”). Now, Weissbluth at some point in his book points out that the circadian rhythm is actually 25 hours and that is why a baby will have off days over so often. This is true, but true only with no environmental cues. With environmental cues, the clock is a bit longer than a 24 hour day.

In babies, the circadian rhythm changes constantly–which means sleep needs change constantly. This is especially true during the first few months. Just when you figure things out, it changes.

The circadian rhythm is present in all animals. It affects eating patterns, sleeping patterns, and migration patterns, to name a few.

A Circadian Rhythm is your internal clock that tells you when to be tired and when not to be tired. Note that a key component, probably the key component, is light. Light=wake up. Dark=sleep. So, changes to your light exposure will impact your natural rhythm.

You know how I often ask you about the sunlight during summer months when you have sleep problems with your children? It is because sunlight impacts sleep.

This is also why you want to keep lights dim as you are getting ready for bed. This is why most experts recommend no TV or other electronics close to bedtime for any aged child. This is why you keep lights dim if you need to visit your child in the night. This is why it is hard to get a child to go to bed during the summer. I am hearing this from moms of kids of all ages right now. We just hit the longest day of the year, and children do not want to go to bed when it is light outside.

This is why we have dark blinds on our kids’ windows. At bedtime, we close the blinds and it is dark enough for nighttime no matter what time it is. It also helps keep the sun out in the morning. Any light exposure in the morning will speed up the time the body naturally wakes up.

Our blinds aren’t perfect; Brayden gets up much earlier in the summer than he does the winter. But they help.

Light isn’t the only environmental factor on your circadian rhythm. There are also social cues that impact your natural sleep patterns. Meal times impact the circadian rhythm (which, by the way, helps me argue against Weisbluth’s argument that food does not affect sleep patterns). You also have temperature, noise, routines, pain, and medication.

There is so much to sleep! It is no wonder it takes so much time and effort to get our babies sleeping well consistently. You need time for the body to adjust. In fact, the circadian rhythm doesn’t really emerge until 2-3 months old. This is the age when you really start to see an impact from light cues and feeding patterns and sleep routines. Now, we all know we can establish good sleep patterns before this age. But this is the age when things really start to self-regulate, so there is less mom-regulated. This is right about the time babies tend to get easier to take care of :).

Okay, so there is some of the science behind sleep. It isn’t quite as simple as we would like it be :).


How useful was this post?

Click on a star to rate it 1-5!

Average rating 0 / 5. Vote count: 0

No votes so far! Be the first to rate this post.

As you found this post useful...

Follow us on social media!

We are sorry that this post was not useful for you!

Let us improve this post!

Tell us how we can improve this post?


Valerie, also known as The Babywise Mom, is the mother to four children. She has been blogging on Babywise and general parenting since 2007. She has a degree in technical writing and loves using those skills to help parents be the best parents they can be! Read her book, The Babywise Mom Nap Guide, to get help on sleep from birth through the preschool years. You can also find her writing at, Today Parenting, and Her View From Home. Read more about Valerie and her family on the About page. Follow her on FacebookPinterest, and Instagram for more tips and helps.

Find me on: Web | Twitter | Facebook


  1. Heidi
    June 24, 2010 / 6:25 PM

    the science of sleep is very interesting esp. with children (very frustrating at times really) I wonder if there is an average age that children do start 'making up for lost sleep' Both our boys (ages 2 and 5) rise at the same time no matter when they go to bed. That makes summertime fun in the evenings hard to stop. We have to really consider if the fun we are having is worth the crabbiness we're sure to take on the following day! :)It seems at least that teenagers have no problem with this, no?? HA!

  2. Jean Lee
    June 24, 2010 / 9:12 PM

    Interesting post. I've been thinking lately whether children need less sleep in the summer? Don't our bodies adjust seasonally to have more energy in the summer and less during the winter? I still put my 13 month old to sleep at 7:30pm even though it's bright out, but was wondering if it would be more natural to wait until nightfall, around 8 pm? I do notice that if I push much past nightfall, say 8:30 pm, she is overtired. I know that I need less sleep in the summertime personally. The reason I ask is because it might help dictate what my child's bedtime will be in the future when she is older. I could say, "It's dark out, time to sleep." Any thoughts?

  3. Jade
    June 24, 2010 / 10:30 PM

    This is interesting. My 3 year old daughter did not take a nap yesterday which is very rare. Her naps are normally 1.5 hours. Today she woke up from a 2.5 hour nap. I was wondering if that was because she didn't nap yesterday. However, my 13 month old does not nap well. I have done babywise with him since he was born and until maybe 4 or 6 months old he took great naps. I can not figure him out these days! He NEVER naps well. Even though I am consistent he is not. If I am lucky he will take one nap that is 1.5hrs while the other is 45 minutes, and thats a good day. Thanks for all your hard work Val!

  4. JenD
    June 25, 2010 / 1:15 AM

    Very timely for me – my husband and I just got in an argument over sleep. He claimed that because my son suddenly started waking up early (sub 6am!) that he must need to go to bed later. I disagreed but didn't know why until I thought about it some more. My son has been sick over the last week and while he seemed to sleep a lot, he was waking up constantly throughout the night and from naps. So I put him to bed at 6:30pm that night (usually goes to bed at 7:30pm) and the next morning he slept past 7am! If I hadn't read Healthy Sleep Habits, Happy Baby as well as this blog I'm sure that I would have gone along with my husband's suggestion. So thankful for all of the great advice from you and experts like Dr. Weissbluth

  5. Dave and Elaine
    June 25, 2010 / 2:45 PM

    The science of sleep (especially in children/babies) facinates (and frustrates!!) me. But I am forever grateful to this website, Valerie, because it has helped me numerous times figure out my daughter's sleep issues. She is almost 13 months old now. It really does pay to educate yourself on the science of sleep concerning babies and children. Saves a lot of lost sleep for everyone!

  6. Rachel
    June 25, 2010 / 5:59 PM

    We love the HSHHC book! I've found portions of your blog helpful as well, although we don't follow BW. What do you think of Weissbluth's insistence that you should never wake a sleeping baby?

  7. ys
    June 28, 2010 / 6:26 PM

    Love the HSHC book and all I learned having 2 kids. Sleep is definitely a scientific process! I never knew this and about sleep cycles,etc. A lot of parents don't because if I mention some things they look at me as if I'm nuts:) But the sleeping patterns can be very frustrating too! Understanding OT and how sensitive these kids are (still at 3 YO and 2 YO) is a blessing and a curse sometimes……sometimes I think the other parents are so laid-back because they don't understand and ignorance can be bliss in a way. But I do know my kids get HOURS more sleep every day and it is helping them and I just remind myself. But I sometimes feel like the sleep part can be one of the most frustrating parts of young children. I wonder when BW parents will stop thinking about it? That's somewhat tongue in cheek but I wonder if it goes away before 18, lol.

  8. Plowmanators
    July 1, 2010 / 4:53 PM

    Heidi, Part if it must be disposition. Kaitlyn will sleep in the next day if she missed a nap or was up late. Brayden usually doesn't, though since turning five, he has started sleeping in some days.

  9. Plowmanators
    July 1, 2010 / 4:55 PM

    Jade, that seems to make some sense. I think I need less sleep in the summer. However, I have never read that anywhere, so I don't know if it is true. Especially if you consider that most children are significantly more active in the summer. More likely, your three year old is just starting the very slow transition toward not taking naps anymore. You are welcome! 🙂

  10. Plowmanators
    July 1, 2010 / 4:56 PM

    JenD, good job!

  11. Plowmanators
    July 1, 2010 / 5:00 PM

    Oh, sorry Jean Lee and Jade. I meshed your comments together :). So Jean Lee, I thought the idea that they might need less sleep could make sense, but isn't ever mentioned in any books I have read.I don't know what time it gets dark for you, but around here in the summer, it doesn't get dark until around 10 PM, which is definitely too late for bedtime. Then the sun comes up in the 5 AM hour–which would give a child only 7 hours of sleep at night. Definitely not enough. I think the clock is better for setting bedtimes. I have heard from lots of parents around here complaining about the late summer nights because their kids refuse to go to bed, then are cranky in the day. Me and one other mom are the type to say, "I know the sun is up, but it is still bedtime" and we are having no behavior issues.

  12. Plowmanators
    July 1, 2010 / 5:01 PM

    Glad to help Elaine!

  13. Plowmanators
    July 1, 2010 / 5:03 PM

    Rachel, I don't agree with it as a general statement. Weissbluth doesn't even fully agree with it, because a couple hundred pages into the book he says when you should wake a sleeping baby. I think he should have done a better job of clarifying from the beginning.I will be doing a post on it 🙂

  14. Plowmanators
    July 1, 2010 / 5:04 PM

    lol YS. Well, I really don't worry about sleep at all with Brayden or Kaitlyn anymore. Our concern is around McKenna getting the sleep she needs. I did worry about Brayden when he was 3, though, so maybe part of it is just learning to relax a bit as time goes on.

  15. bethanyg
    January 30, 2012 / 7:19 PM

    Thank you! This entry really helped this first time mom of a 7 week old boy. I am looking forward to more stabilization.

Leave a Reply