It is well known that babies cry just before sleep. Sometimes the cries have specific origins that cause pain or discomfort. But as everyone knows, even when all those factors have been eliminated every baby still appears to cry in an attempt to fight sleep itself.
This question is NOT asking for a solution. This is a scientific question. I am asking why? Why do they fight sleep? Is there a survival advantage? Is there a physiological explanation? What research has been carried out into it to determine the reason for the "sleep fight"?
Could it be that a good cry before sleep actually has a physiological payoff that confers a survival advantage? Does it "prepare" the baby's breathing pathways before sleep, for example?
Are there some meta-analyses or epidemiological factors we can do to check this hypothesis? Are those babies that die of SIDS those that do not cry as much before sleep? Is there any epidemiological data to test such ideas?
Hi Derek - As a new mom, I've been extremely frustrated with the amount of anecdotal 'expertise' bandied about with regards to sleep. But here are a few studies that I've found.
1) One study investigating the extent to which fussiness (related to sleep or not) was an individual variable or a marker of developmental stage: http://onlinelibrary.wiley.com/doi/10.1111/j.1467-8624.1996.tb01872.x/abstract Worth a read.
2) A review of night-time wakings and behavioral interventions. (attached) What the success of these interventions suggests to me is that cry-it-out (CIO) works for many parents but doesn't answer the question of why many (though not all) children cry prior to sleep and if there's a way to avoid that crying altogether. The review also doesn't address any attachment or other issues that might be corollary to CIO.
3) A German paper had some interesting insights as well. Here's the abstract:
The co-morbidity of crying, feeding and sleeping problems at 5 months of age was investigated in a representative sample of 432 infants in South Germany. A crying, sleeping or feeding problem was reported in 32.7% of these infants by their parents and a further 14.6% had two or more of these problems. Little co-morbidity between crying and feeding problems was found. There were moderate to strong associations between crying and sleeping behaviours. Feeding problems showed little relationship to sleeping behaviour, but feeding type and frequency of feeds were related to night waking. Breastfed infants woke much more often at night. Crying and feeding problems at 5 months were poor predictors of sleeping behaviour at 20 or 56 months of age. Later sleeping behaviour was best predicted by infant sleeping behaviour. At 56 months, maternal distress due to sleeping and co-sleeping practices was predicted by maternal distress due to crying and feeding practices at 5 months of age. The predictions were significant but generally weak to modest in strength. Future studies on the consequences of crying or feeding problems should take into account patterns of co-morbidity. So-called ‘post-colicky’ sleep problems are not due to increased crying per se but rather appear to be the consequence of associated infant sleeping problems and parental caretaking patterns for dealing with night waking in infancy.
And the paper itself: http://onlinelibrary.wiley.com/doi/10.1002/edp.2430040405/abstract
4) Finally, a more recent survey of parenting methods has some interesting insights. I've attached it here as well.
I think not every baby cries to fight sleep. My baby always cried before nocturnal sleep until I had discovered that he was subjected to noise during his day sleep and at 6 p.m. when he was supposed to begin his nocturnal sleep, he was too tired to get asleep. I do not think there is any scientific answer to your question. Each case may have individual reasons, but I think it is good to take care that a baby do not have too many stimuli, which could interfere with its sleep. Any mother should be sensitive to her baby's needs and find the proper solution.
Perphaps babies are seeking comfort. I wonder if babies in orhanage cry so much as babies living with their parents. If the do then my hypothesis is wrong.
It is fact though that when newborns, infants even grown up children are overstimulated by playing, too much talking from adults, watching tv (when they are older) then they usually have a good cry before sleep. So maybe crying allows them to "let some steam off" and relax enough in order to sleep.
From my experience with babies, I do not think that their crying is positive in any sense, but it is always a demonstration of some need, discomfort etc. One more story about the baby I knew (my nephew). In his first few months he was crying very much. His mother went from one doctor to another, always getting the answer: "don't worry, he belongs to the class of babies who cry during the first months, and grow up from this later". But my sister in law was stubborn and every time looked for another doctor, until the last one diagnosed pylorus stenosis. The remedy was simple: the baby had to get thickened milk instead of plain one. If she had not find this doctor, the baby would have received thickened milk about his third month and the legend of "baby crying for nothing" would be strenghtened. I don't believe in babies crying for nothing.
Just a reminder: I'm not looking for a discussion about solutions. I'm looking for a discussion of scientific studies that have investigated this question (if any).
I was just trying to say that it is not a problem for scientific studies, since there is always a reason for baby to cry, there is not a mysterious "sleep fight".
I am told that babies cry when they are sleepy because they actually 'want' to stay awake (because there are many exciting things to do when they are awake). Naturally, this is an adult interpretation. I am not aware of any scientific studies. To test this attention-based hypothesis, clearly the babies must be split into a test group and a control group. The test group babies must be subject to interesting stimuli, whereas the control babies must be placed in an environment that is absolutely boring. I figure It must be awfully difficult to convince parents to let their babies be a control sample. They might just cry all the time because it is so boring.
I would rather say that they want to sleep but are too tired to get asleep. It is again not the scientific explanation, but it happens to grown-ups, too, that they are too tired to get asleep. Babies can be more prone to tiredness; some advices for new mothers are to keep babies in "normal" environment (meaning noisy, normal for grown-ups). Not every baby is able to get used to it. Your "control group" certainly would have any problem with sleep, but may be slower in development.
There are legitimate reasons why babies would cry on a given night or at a naptime that could be from unmet needs (hunger, dirty diaper, etc.). I've gone through several of the books out there about sleep and the debates about whether we should let kids cry or respond immediately when it is time to sleep. From what I can tell from the books I've read, the authors are sharing anecdotal evidence or their own parenting experience, but not really basing this on actually studies.
I can say from my own experience that consistency around bedtimes makes a lot of difference. As long as kids have had a somewhat consistent routine during their dinnertime and bedtime, then they begin to wind down and calm themselves so that they are prepared for sleep. In that case they don't cry on many of the nights. My research area is on routines for children and how routines affect sleep, health, and well-being outcomes. I have seen in our data that kids who have more consistent mealtimes and bedtimes tend to have better sleep outcomes and less stressed mothers. This could be an artifact of having more planned households, but infants definitely seem to thrive on consistency.
From personal experience with my own kids, they cry sometimes at night if they are extra tired. It is almost ironic, but on the days where they don't sleep much for naps they seem to be more tired and yet fight sleep more at night. So perhaps the fight/cry at night is related to more stress or fatigue from the day. I think that a great study could be developed that looks at affect and reactivity at bedtime in relation to hormone levels and schedules from earlier in the day.
Every parent would probably have their answer as to why their baby cries, but maybe there is some truth to the idea that babies don't want to miss anything. It could also be that they are anxious to be alone. I think maybe we flatter ourselves supposing that we are so exciting that babies just can't deal with the thought of having to miss all of the amazing things we do every day!
True about the plethora of anecdotal descriptions. The nature of my question is to move into the scientific realm and discuss what hypotheses are testable, how we should do the tests, and what has already been tested (if any).
I am not interested in any anecdotal answers :-)
You seem not to understand that the story about sleep fight is anecdotal itself, so looking for scientific hypotheses is nonsens.
I don t know if same one studies the relationship with GER but in my experience a lot of babies with Upper airway symptoms of reflux cry when they are sleepy . Do you think is a realistic hypotesis ?
My only expertise here is that I participated in the rearing of two of the little critters myself. I don't believe that babies cry to avoid sleep. I think they cry because they are tired or uncomfortable. That crying may or may not delay the onset of sleep, which, if it does, perpetuates their discomfort. I also can contribute two data points to refute an assertion you made. To whit:
"...every baby still appears to cry in an attempt to fight sleep itself."
Not EVERY baby. My two babies, with the exception of the times that there was something more-or-less identifiable causing particular discomfort, mostly fell asleep without any fuss.
Have you thougth about the possibility that crying before sleep could be a mechanish to relax theirselves?. After crying normally you feel more relaxed, and perhaps they use crying as a sleep inductor. It would be possible to measure using accelerometry the difference in time to get asleep between those children who cry and those that don´t do it.
at the age of 4-6 month start babies/infants to realize the to fall asleep could mean, that the mother is leaving. It is a naturally reflex to avoid the the mother goes away. This theory could explain that most infants cry, struggle or respectively fight against to fall asleep.
Refer to my reports about ADEL Ankyloglossia with Deviation of the epiglottis and Larynx); Colic cry is caused from respiratory insufficiency. After the operation on the ADEL (CHL/EVO) cry decreases greatly and its sounds are heard tranquil.
Are we sure that babies cry to fight sleep? This is my impression from our daughter, but it could be that the strong correlation between crying and sleeping is caused by a high probability of falling asleep after crying and fussing.
Hi Derek - As a new mom, I've been extremely frustrated with the amount of anecdotal 'expertise' bandied about with regards to sleep. But here are a few studies that I've found.
1) One study investigating the extent to which fussiness (related to sleep or not) was an individual variable or a marker of developmental stage: http://onlinelibrary.wiley.com/doi/10.1111/j.1467-8624.1996.tb01872.x/abstract Worth a read.
2) A review of night-time wakings and behavioral interventions. (attached) What the success of these interventions suggests to me is that cry-it-out (CIO) works for many parents but doesn't answer the question of why many (though not all) children cry prior to sleep and if there's a way to avoid that crying altogether. The review also doesn't address any attachment or other issues that might be corollary to CIO.
3) A German paper had some interesting insights as well. Here's the abstract:
The co-morbidity of crying, feeding and sleeping problems at 5 months of age was investigated in a representative sample of 432 infants in South Germany. A crying, sleeping or feeding problem was reported in 32.7% of these infants by their parents and a further 14.6% had two or more of these problems. Little co-morbidity between crying and feeding problems was found. There were moderate to strong associations between crying and sleeping behaviours. Feeding problems showed little relationship to sleeping behaviour, but feeding type and frequency of feeds were related to night waking. Breastfed infants woke much more often at night. Crying and feeding problems at 5 months were poor predictors of sleeping behaviour at 20 or 56 months of age. Later sleeping behaviour was best predicted by infant sleeping behaviour. At 56 months, maternal distress due to sleeping and co-sleeping practices was predicted by maternal distress due to crying and feeding practices at 5 months of age. The predictions were significant but generally weak to modest in strength. Future studies on the consequences of crying or feeding problems should take into account patterns of co-morbidity. So-called ‘post-colicky’ sleep problems are not due to increased crying per se but rather appear to be the consequence of associated infant sleeping problems and parental caretaking patterns for dealing with night waking in infancy.
And the paper itself: http://onlinelibrary.wiley.com/doi/10.1002/edp.2430040405/abstract
4) Finally, a more recent survey of parenting methods has some interesting insights. I've attached it here as well.
Sorry one of the attachments didn't go through (#2). Attached here. I'd love to hear your thoughts about these studies.
Itiis cause by ADEL.Mukai S. Ankyloglossia with deviation of the epiglottis and larynx (ADEL) Ann Otol Rhinol Laryngol Suppl, 1991, SUPPLE 153, PP3-21.
My five cents. Maybe the issues could be tackled from an evolutionary point of view. Primates, but also babies growing in traditional societies, live in constant contact with their mothers and co-sleep during the night (Jared Diamond "The World until Yesterday: What Can We Learn from Traditional Societies?"). This allow babies to suckle from mother breast both for feeding and for soothing. However, in moden societies this is often not feasible as few mothers wish to go to bed at 7 p.m. and function as human pacifier.
Crying stimulates milk production in mothers and milk contains chemical that promote sleep?
Dear Hanno,
A young mother with a new born baby told me once that when she heard her baby crying that she felt a flux of milk towards the nipples of her breasts she could not control (neuro-endocrine response/reflex?). In addition, people also suggested to drink (warm) milk before going to bed which may favor sleep states (pers. obs.)....
Alternative, not mutually exclusive, explanation:
Interesting is that in primates young offspring are permanently physically attached to the mother, or not? Why is this often not the case in humans? Is that the cause of expressed discomfort in human babies expressed before so-called sleep, e.g. a feeling of a lack of physical protection as in young primates physically disconnected from the mother?
Why are human babies calmed down by artificial objects resembling components of the mother (artificial nipples) or calm down when they have something attached to the body?
For whatever it’s worth, I would love to see research, empirical or theoretical, in this area. However, one thing I can say for sure is this: It is NOT “nonsense“ to attempt scientific study of this question. It is important and fascinating. Derek, I wish you the best of luck! ( if I run across anything relevant, I will jump back into this discussion.) Sorry I can’t contribute something more concrete.
I have a totally different hypothesis. The reason babies sleep so much is presumably for learning and memory consolidation. Since babies are learning so much about their new world, they need to do a lot of this, and the times when sleep is needed the most may reflect times when "too many" new experiences have been encountered, and there is a "backup" in the hippocampus, with an urgent need to deal with the backup, requiring sleep immediately.
I was thinking...if this is true, could it be that the experience of such an overload in an infant is either painful (like a seizure), terrifying (like a nightmare), or simply disorienting, like suddenly finding oneself in an unfamiliar environment? And that is why they cry at these times?
It is caused by respiratory insufficiency. See my articles about ankyloglossia with deviation of the epiglottis and larynx. Annals of Otoaryngol 100,supple 153 etc.
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