Let’s Face It: Formula-Fed Babies Sleep Better

Breastfed babies tend to arouse from sleep more easily and sleep for shorter periods of time. Nearly all babies who sleep through the night by 3 months are formula-fed.

Breastfeeding is a major battleground of the modern mommy wars. In her widely discussed piece in The Atlantic, Hanna Rosin called breastfeeding the “new sucking sound”–replacing vacuuming as the task that shackles women to the house, promotes the unequal distribution of childcare and household duties, and prevents women from reaching the upper echelons of professional success. The benefits of breastfeeding have been oversold, she claims, and–just as significantly–the costs to women’s sleep, time, and career progress have been downplayed.

On the other side of the debate, the American Academy of Pediatrics states that the benefits for the infant in terms of reduced risk of infection, adult obesity, allergies, and asthma are so great that breastfeeding must be viewed as an “investment in your child’s future” rather than a “lifestyle choice.” Some lactation consultants fall into this camp too, needing to be reminded to suppress their impulse to sigh when yet another mother complains of exhaustion and lack of sleep, for fear they alienate her–and thus fail to convince her to keep breastfeeding.

On both sides, well-intentioned but overzealous advocates twist the evidence on breastfeeding, cherry-picking among studies to support their preexisting views.

This is especially true when it comes to one of breastfeeding’s major downsides: Disrupted sleep.

Consider the post, 5 Cool Things No One Ever Told You About Nighttime Breastfeeding, which claims that the number 1 coolest thing about nighttime breastfeeding is “breastfeeding moms actually get MORE sleep than their formula-feeding counterparts,” and concludes with the rhetorical question: “Did you ever think, when you hear your baby rouse at 2:00am, that they are actually giving you the gift of MORE sleep…?”

To which I would like to respond: No, never, not only because it does not square with my own experience, but also because the research on this topic is clear: breastfeeding moms, on average, get less sleep, not more.

Almost without exception, studies on formula feeding, breastfeeding, and sleep find that breastfed babies wake up more often than formula fed ones at night, and breastfeeding mothers therefore get LESS uninterrupted nighttime sleep.

Nighttime Wakings in Formula-Fed Versus Breastfed Babies

2003 study, in which researchers followed 253 newborns for their first 3 months of life, is a case in point. Parents reported their feeding practices (formula, breast, or a combination) while tracking how frequently their babies awoke in the middle of the night.

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Two-thirds of the babies in the study slept through the night at the end of the third month–almost all of these babies (94%) were formula-fed. While 79% of formula-fed 3-month-olds in the study slept through the night, only 15% of breastfed 3-month-olds did.

This 2003 study is small. So by itself it would not be terribly compelling. But scores of other studies find the same pattern: breastfed babies spend less total time sleeping and wake up more frequently at night. Some studies even find formula-fed babies sleep more at night than breastfed babies as early as four weeks of age.

The evidence is strongest, though, for older babies. Breastfed babies and even nursing toddlers are more likely to wake up to feed in the middle of the night. Much more likely. According to a recent Australian study of 4,507 babies, at 6 months of age, breastfed babies were 66% more likely to wake up in the middle of the night. (See additional studies here and here.) The evidence is so strong infant sleep researchers generally state formula-fed babies’ longer nighttime sleep as a fact.

The Evidence Cited By Breastfeeding Advocates

Only two studies deviate from this general pattern. In the first, researchers measured how much nighttime sleep 133 mothers were getting at 3 months postpartum. Exclusively breastfeeding mothers slept 45 minutes longer at night, on average, than did mothers who formula fed or supplemented with formula.

In the second study, researchers compared the nighttime sleep of 19 mothers who were 9-16 weeks postpartum and 61 mothers who were 2-13 weeks postpartum. No significant differences were found in sleep duration or self-reported fatigue between formula and breastfeeding mothers. Breastfeeding mothers did tend to report less sleep, but the difference was not statistically significant.

These two studies are small and inconsistent with the rest of the research. Their findings may simply be anomalies. On the other hand, unlike the rest of the research, these two studies focus on mothers’ sleep rather than babies’ sleep, and this could be why they do not find much of a difference between the formula-feeding and breastfeeding mothers. Most newborns, formula or breastfed, wake to feed at night. Formula obviously takes longer to prepare than breast milk. So when their babies do wake up, formula feeding parents end up being awake for longer and getting less total sleep.

In response to the second of these two studies, a pediatrician wrote in to make the same argument :

Dear Authors,

I appreciate your study in this area however your conclusions do not represent my personal practice experience. I have spoken with thousands of mothers; perhaps you would have a different conclusion if your sample size was bigger.

Newborn feeding patterns are similar initially. Mothers that breast feed have at least one to two night time feedings from 2 to 12 weeks. However, by about 8 to 10 weeks formula fed babies that can eat at least 6 oz with 4 daytime feeds can sleep a solid 12 hours at night. I have seen this pattern hundreds of times. Mothers that have a formula fed infant that follow the above pattern are much more rested.

Even though breastfeeding is more time intensive and more sleep depriving it is far superior to formula and I highly recommend it to all of my moms…

But why do formula-fed babies sleep for longer stretches and wake less frequently at night?

When I’ve brought up these findings, a number of people responded, “Well, of course, breast milk is less filling than formula.” This is the most commonly offered explanation: breastfed babies become hungrier sooner and therefore wake up in the middle of the night to feed. And it’s true: breast milk is digested more quickly than formula. For newborns, staying full for longer stretches may help them sleep for longer periods of time.

But here’s the thing: breastfed babies continue to wake up more frequently throughout their first year and into toddlerhood. By 6 to 9 months of age, babies’ stomachs have increased in capacity, and most are eating solid foods. Why are they still waking up?

One possibility is that breastfeeding mothers tend to nurse their infants back to sleep. A large study of just over 10,000 babies found that breastfed babies woke up more at night, but only if they were nursed back to sleep. Unfortunately, this study was cross-sectional, so it cannot tell us whether night nursing causes night wakings or is caused by them.

One recent clinical trial does suggest that night nursing causes night wakings. Beginning when their babies were 2 weeks of age, an intervention group of exclusively breastfeeding parents was instructed to offer a focal feed sometime between 10 pm and midnight. If the newborn woke up again before morning, the father was to attempt to soothe the baby by re-swaddling, changing diapers, and walking–basically, by any means possible save feeding, to gradually lengthen the time between nighttime feeds. By 8 weeks of age, 100% of breastfed infants receiving the intervention (compared to 23% in the control group) were “sleeping through the night.”

(I was very excited by this study until I read the fine print. Only by the painfully low standards of new parents could these newborns be said to “sleeping through the night”, which was defined as not waking up between midnight and 5:00 a.m.)

Sleep Benefits of Breastfeeding

There are some sleep benefits associated with breastfeeding. Breast milk’s unique hormones and proteins appear to directly affect infant sleep patterns. Breastmilk contains numerous sleep-promoting hormones and proteins, such as melatonin, delta-sleep-inducing peptide, tryptophan, and prolactin, among others. The release of these hormones and proteins tracks the mothers’ own circadian rhythm and may help entrain newborns’ own circadian rhythms, helping them distinguish between daytime and nighttime.

(Note to new mothers who are pumping: night milk is not the same as day milk!)

Perhaps because of these sleep-promoting hormones, breastfed babies also arouse more easily from active sleep. This tendency probably contributes to breastfed babies’ lower risk of SIDS, but likely also makes them more prone to night waking.

To handle fragmented sleep, nature appears to have provided nursing mothers with some recompense. Despite formula-fed infants waking up less in the middle of the night, nursing mothers benefit from high levels of sleep-inducing hormones like prolactin, experience more than double the normal duration of nocturnal slow wave sleep, and may be able to sleep during night-time feeds, particularly if co-sleeping.

What Is The Natural Sleep Pattern For Babies?

It is hard not to look at the evidence and conclude that, much to the dismay of exhausted parents, nature did not intend for babies to reliably sleep through the night. Evolutionary psychologists have even argued that infants nurse at night to prevent their mothers from becoming pregnant again. A younger sibling uses up precious resources, threatening the baby’s health and survival.

The mother’s reproductive fitness is in conflict with her baby’s fitness, according to this theory. A mother’s reproductive fitness is maximized by having relatively short intervals between births (the risk of child mortality is higher, but a larger total number of children survive). But the baby’s survival is maximized by a long interval between his or her birth and the next birth.

The Bottom Line

Natural or not, breastfeeding usually entails many additional months of broken sleep, and a prolonged period of broken sleep can make caring for a new baby, returning to work–and just about every aspect of existence–pretty miserable. As I can personally attest, suffering through months of broken sleep is not only about fatigue or a mild mental fogginess that can be masked by an extra cup of coffee–or four. Consistently poor sleep heightens hostility, clouds our thinking, adds stress to the already major stress of caring for a baby and–not surprisingly–increases the likelihood of postpartum depression. These problems are bad for mothers and bad for our babies.

So yes, women should certainly be told about the positive effects of breastfeeding. But it is offensive, paternalistic, and intellectually dishonest to provide false or cherry-picked information on breastfeeding’s downsides. These downsides exist. And no one benefits from brushing them under the rug.

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Author: Amy Kiefer

As a former research scientist and proud mama of three little munchkins, I love digging into the research on all things baby-related and sharing it with my readers.

28 thoughts on “Let’s Face It: Formula-Fed Babies Sleep Better”

  1. This was a really interesting post. I have a personal theory that a big part of the difference between breast and bottle feeding at night is actually due to the bottle, not the use of formula.

    For the most part I pumped while bottle feeding over night (not as bad as it sounds, you can do them both at once), because the baby slept much better than when I tried to breastfeed directly. A couple other people I know independently settled on the same system for the same reason. When I tried to breastfeed at night my baby would fall asleep so fast that I don’t think she was actually eating very much, so my best guess is that the better sleep was due to her eating more per feeding.

    I wish someone would do a study on this! It would be so interesting to see how the sleep habits of formula fed babies compare to those of babies who are bottle fed breast milk.

    1. That’s really interesting. Your experiences square with my own. For our two, it seemed like breastfeeding from the breast was super rewarding. So rewarding that they would wake up earlier and earlier if they got to breastfeed first thing in the morning. Neither were that into the bottle. Maybe I should have pumped at night from the beginning 🙂

  2. Oh dear, I’m commenting again.

    I’d be far more interested in studies that measured the parenting ‘styles’ as well as the data on sleep for formula vs breastfed..

    For example, I would suggest breastfeeding for a longer period of time may go hand-in-hand with parents who either co-sleep or have the baby in their room for far longer than those who formula feed. A generalisation, but unless the study included it, how do we know?
    Surely for these studies to be accurate, they have to include many other factors. Even something like expectations of when the baby would sleep through the night. I had an expectation that was what our family needed to stay sane, so I tried solutions until we *kindof* achieved that goal (no-ones baby sleeps through the night 365 days a year right!)
    How many of either tried other ways of resettling rather than a feed (formula or breastmilk) I know I probably would have tried dropping night feedings far earlier if I’d been using formula. And I dropped them relatively early & met almost immediate success at sleeping (properly, like 11 hours) through the night. It’s a lot more stressful to attempt to not breastfeed than to not prepare a bottle until you really feel they aren’t going to settle. Most of my breastfeeding friends that have babies that are waking at night, admit themselves they aren’t ready to cut the night feedings.

    Or what about whether there are single parents vs couples parenting these babies? Or even further, does the dad get up? Again, I couldn’t have dropped night feedings without a husband who was willing to get up a few times a night for a few nights (& his reward? Oh so much more sleep!!)

    Surely that’s only the start of the probable differences that may have patterns, and some of them are such subtle things..
    Even on the opposite side, do the breastfeeding mothers sleep longer because they generally try to make healthier choices which may contribute to their amount of sleep? Although I doubt this because many formula feeding mothers are equally, if not more healthy! But how do we know without these factors being included in a study?

    Honestly though, this is a great article, it gets the brain wheels turning for sure.

    Speaking of cherry-picking, although I breastfed #1 until he was 1 year old, I did not enjoy much of it at all. There is not one bit of me that misses it. I’m not sure #2 is going to get to a year if it’s the same second time around. Theres plenty of benefits but I think you have to be pretty committed & rid the ‘fairy-tale’ to actually continue breastfeeding when its not something you love. I do feel some friends simply had no stickability & gave up because it was harder than they expected.. In which case, we should have helped with their expectations & said that, quite frankly, although it’s great for your baby, it can also be a totally crap experience for you!

    1. I have not seen any studies on parenting styles and sleep, but I think you are right, part of the reason breastfed babies wake up more often is that their mothers often feed them to sleep. Oh, those sleep associations. Once formed, they can be so hard to break. With my second I was very careful to put her down drowsy but awake as often as possible from about a month on, so we never had to do full on sleep training. My husband, like yours, just had a few nights of giving her a bottle of water to get her drop her night feeds around 5 months.

  3. I would also chime in that preparing a bottle at night takes more time than opening your nursing cami (or whatever you’re wearing) and sometimes the baby self settles before the bottle is ready. My second baby who is 4 months old (3 months corrected age) doesn’t like her formula cold and so, has to wait until it is warmed up. About half the time, by the time I would do that she has fallen back asleep. I feel like the act of preparing a bottle has forced her to learn to self soothe sooner than if we were nursing. She sleeps 7 hours at least at night now, sometimes longer if her daytime intake was good. My first daughter breastfed at night and she did not sleep through the night even once until close to 6 months. We coslept with her also.

  4. Thank you for this. I had to stop nursing altogether and start pumping and supplementing with formula due to a severe early case of PPD/PPA brought on by the sleepless nights of breastfeeding in the early weeks. It was difficult to “give in” to formula at first but it was encouraged by my doctor as well as my LO’s ped in an effort to help protect MY sleep. So many studies and brochures and lectures are based on how BFing is best for baby and completely neglect the other side of the equation, the mother. I learned that my needs are just as important as my baby’s and caretaking required a rested mom.

    Our solution was to do formula at night and pump-to-feed during the day. Those who say that “formula makes your baby sleep longer” is a myth are probably just trying to sell you on exclusively BFing because our LO slept in 4-hr stretches once we introduced it at 12 days old and she started sleepin longer stretches by 2 months. Sleep is the most important thing to a new mom, especially one on the verge of PPD. My ped firmly believes that a sleep-deprived parent is a risk to an infant.

  5. This is repulsive and complete crap. Sleep is developmental. Even if this was true at all your really going to choose sleep over whats best for your baby!? As a mom of 4 3 formula one breastfed i can tell you your not going to sleep either way. So if any mamas are reading this on the verge of quitting breastfeeding DONT quit your doing the BEST thing for yourselt and your baby!!!!

    1. This is not a well formulated or open minded comment, but I am allowing it to be posted because it underscores a couple troubling aspects of “the breast is best at all costs, don’t worry about your own sleep, that’s selfish” perspective. First, the evidence is the evidence, whatever it implies about your life or your parenting decisions. Here the evidence suggests that breastfed babies wake more often than formula fed babies. This is probably not true for all babies, but it is a large and consistent finding in most studies. I reject the assumption that we need to only present evidence if it agrees with a particular agenda. Second, I think the breast is best under all circumstances, for all women is patently false. Sleep is important for everyone, especially new mothers. A lack of sleep can have serious immediate and long-term consequences for both women and their babies, and I trust women to weigh these costs against their desire to breastfeed. Their decision to breastfeed completely, partially, or not at all is a deeply personal choice, informed by their individual circumstances, and I cannot imagine telling any other woman what is right for her and her family.

      1. I totally agree. Breast is, I believe best, if there no other factors. But there are other factors. Sleep deprivation can have huge consequences. Post-partum depression is largely associated with sleep-deprivation. Beyond depression you can be a danger to your children if you drive them while exhausted. Your family may depend on your income and if you are so exhausted you risk losing your job and your ability to house your children, this does not serve anybody. I breastfed, exclusively, for about a year. I didn’t lose 15 minutes of sleep, I lost hours and hours and hours. I persisted, but I had help and support around me. Not all mothers are that lucky. I thought the post was a well-balanced discussion of the evidence.

    2. Maybe the best for their baby is to give up? I pumped for 3 months with my first and drove myself insane because people kept saying ‘don’t give up’. Only after switching to formula I realized I was only being a food source and not a mother. I was too exhausted for cuddles and playtime. Once I switched, my baby slept twice as long after only a few days and I build my energy back up and had so much more time for her instead of her food. I felt so guilty I’d pushed it for 3 full months and will never get them back. My son is 3 months old now and has been on formula from the start. I feel guilty on my first because I’m enjoying this time so much more than I did with her. That’s something I cannot change and will never get those precious first few months with her back.

      1. You have expressed my experience exactly! I tried breastfeeding, but my son was not latching well. I tried to pump as an alternative, but was not making enough. I had to supplement with formula regardless, while I was trying to increase my supply by pumping every 2 to 3 hours. Between that, feeding him, and cleaning the equipment, I was very sleep deprived. All this while also recovering from a c-section. Even if I managed to get enough hours of sleep, it was so scattered that it was taking a huge toll on my mental health. I realized (after much reading) that the benefits to my child of having a less stressed and irritable mother would outweigh any benefits of breastfeeding, which I do believe are overstated. I do believe the science supports it being helpful to prevent infections and possible digestive issues, but even then, it just reduces the risk, not eliminates it. I imagine breastfed babies aren’t magically never sick. As a person who majored in statistics, I get very annoyed when people use correlational studies to claim causation, particularly when there are clearly other factors at play when it comes to how a child develops.

  6. The idea of 79% of formula fed babies sleeping through the night at 3 months is astonishing to me. Mine was waking up twice a night until 7 or 8 months, and once a night until 1 year.

  7. There’s a lot of factors here. 1) You can breastfeed only half awake. You can’t really make a bottle while half-awake. So sleep quantity vs quality is a big deal. 2) I bet sleep associations are associated with breastfeeding, i.e. baby waking up to check if mama is still there. The only way to account for that is to not co-sleep have mom wake up, pump, then have dad give the baby the bottle and see if the sleep pattern changes. I’m not recommending this and it’s totally ridiculous but that would be the way to eliminate the associations. 3). A not-insignificant portion of women struggle with milk production. They produce less milk during a feeding and thus have to feed more often. This results in a baby’s stomach not expanding as much much as formula-fed babies and leads them to develop more frequent feeding habits. If these studies could sort for women who have that problem, that might be a new way to cut the data that could provide a different insight.

  8. I am not sure when here you are getting your conclusion. Science and research shows that in long run breastfed babies sleep better and mommies too. If my baby wakes up more frequently then he straight away goes to sleep. I don’t have to carry him or rock him or walk with him or sleep train him with all those cries. As oxytocin hormones are produced when breastfeeding so post natal depression is not that common in breastfeeding mums. But PND can happen when mothers are left alone with the baby with no support through out the day. Eastern countries have relatives or village to help the new mum. In western countries this is not available so people go extremes.
    Breastfeeding also helps to avoid many cancers in mothers. Also it protects baby from everything or most of things, increases their immunity. When a mother kisses baby’s cheeks or mouth brain of mother is triggered to produce nutrients that baby needs and is given by breastmilk. Like every mother produces customized milk for each of her children. This is a miracle by nature.

    Now saying that there could be reasons for which a mother can’t breastfeed the baby e.g. less supply, prior commitment but it should be her choice but such baseless articles influencing a sleep deprived mother. Let the mother make the choice.

  9. I’m not sure that I feel confident in this article’s assertion, when doing my own research I’m finding other studies that do show breastfeeding mothers sleep is actually longer, not listed here (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3927438/). I absolutely agree about the importance of sleep and families need to make decisions based on their own personal circumstances but I have also seen evidence presented about how babies are wired to wake at certain intervals and that it is unrealistic for parents to expect this to happen, which doesn’t seem to be captured here either (http://evolutionaryparenting.com/myths-and-facts-about-night-wakings/). This rings true for me as I had one who woke every 45 minutes and the other who woke twice a night and I did the same thing with both. I also have a friend with twins, one breastfed and the other bottle fed and method of feeding made no difference in nighttime waking. I am still unconvinced that there is a magic pill to escape the challenges of being parent and being woken up at night called formula, but I do think that helping all mothers get more sleep by helping with other children and cooking and chores so they can catch up during the day with babies is something we can all do that will definitely help.

  10. An interesting article. I breast feed and cosleep with my 7 month old, and he wakes up multiple times a night. I never really planned to do this but it’s working fine. I think because we cosleep, I barely wake up to nurse and fall back to sleep very quickly (and nurse lying down). I’ve also read research suggestion that cosleeping, breastfeeding mums and babies end up synchronizing their sleep cycles. For me, getting him to ‘sleep through’ isn’t that important. I think research should focus on mums reporting of their sleep quality or measuring levels of sleep deprivation, rather than seeing numbers of night wakes as the important factor. It would also be interesting to see some cross cultural studies on this in places where breastfeeding and cosleeping is the norm.

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