Do babies sleep better when they start solids early?

Have you seen headlines recently about a study showing that feeding babies at 3 months helps them sleep better at night? I have. The nonmedical press is not very good at reporting on medical studies and tends to put out sensational headlines with very little data. I was curious about this study, because this directly contradicts the recommendation to exclusively breastfeed for the first six months with no other foods introduced. I took a look at the original study, and here’s what I found.

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The Background
The study is out of the UK where a survey in 2010 found that only 1% of infants are exclusively breastfed for 6 months and that 75% of parents had introduced solids by 5 months of age. Of those, 52% introduced solids because they felt like milk was no longer enough for their baby; 29% felt that the baby was developmentally mature enough; and 26% did it because their baby was waking up at night. In the UK (like the US), parents are recommended to exclusively breastmilk feed for the first 6 months and not to introduce any cereals or other complementary foods until after their baby is 6 months old.

The Study
The Enquiring About Tolerance (EAT) study was a randomized clinical trial of 1303 infants comparing early introduction of 6 allergenic foods at 3 months versus exclusively breastfeeding for 6 months followed by introduction of allergenic foods after 6 months. The study was investigating whether earlier introduction of allergenic foods would decrease later development of food allergies. As part of the study, parents completed a validated sleep questionnaire (the Brief Infant Sleep Questionnaire) 15 times between 3 months and 3 years. The questionnaire asked about infant sleep location and position, daytime and nighttime sleep duration, number of night wakenings and total time awake at night, time spent settling, soothing technique, what time infant went to sleep, and an overall rating how problematic parents rated infant’s sleep. They also completed questionnaires to assess what infants were eating and how well they were tolerating it, and 3 times, mothers completed the World Health Organization Quality of Life questionnaire. While sleep changes were not a primary focus of the study, the study was set up in a way to analyze infant sleep data as a secondary outcome measure.


The Data
Questionnaire noncompletion rates were higher in the EIG group, although the authors evaluated the data and did not think the missing data affected their evaluation. The study found that infants in the EIG group had increased nighttime sleep duration that persisted past 1 year of age. Don’t get too excited and start feeding pureed carrots to your 3 month old quite yet. What was the difference? An average of 7.3 minutes longer. With the 95% confidence interval 2 minutes to 12.5 minutes. What that means is that their group slept an average of 7.3 minutes longer. Based on the size of their group (which was a good sized group but wasn’t every baby in the world), they can calculate that the real effect is somewhere between 2 and 12.5 minutes. It could be 7 minutes. It could be more. It could be less. The important point here is that it’s not hours. You shouldn’t feed your 3 month old pureed carrots and expect to suddenly start feeling well rested. The peak difference was at 6 months with 16.6 more minutes of sleep. The EIG group experienced 9% fewer night awakenings over the course of the study, which might explain the increased time asleep. As expected, parents’ perception of infant sleep problems correlated with maternal quality of life measures and with infant nighttime sleep duration and number of night awakenings. One thing that the authors noted is that a lot of the parents found it difficult to fully follow the recommendations for allergenic food introduction in the timeframe recommended, so only 42% of the infants in the study fully followed the recommended protocol. Those infants had significantly better nighttime sleep characteristics. They also noted that infants in the EIG group who had better sleep at the time of enrollment (before starting any solids for the study) had better adherence with the food introduction strategy of the study, which may be related to developmental maturity helping with both solidi food introduction and improved sleep. They also found that the heaviest infants at enrollment slept the longest at night but that the infants that had gained the most weight from birth were more likely to be waking at night consistent with the idea that they wake more because they need to eat more to support their growth.


The Evaluation
The idea that feeding babies solids will help them sleep better at night is common. Parents may have been influenced by this idea when filling out the infant sleep forms. They knew their baby was getting solids, so they expected the baby the sleep better. These types of unconscious biases are hard to avoid. Most of the infants were still being breastfed at 6 months. On the other hand, they were participants in a feeding study and knew it, so the mothers may have been influenced to continue breastfeeding when they might have otherwise quit. It is important to note that the statistical evaluation was done on something called an “intent to treat” model. All of the infants in the EIG group were treated as though they had received allergenic foods according to the study design, and all of the infants in the SIG group were treated as though they had not received any solid foods and were exclusively breastfed. In fact, 23% of the infants in the SIG group had received solids by 5 months and 70% had received solids by 6 months, while only 66% of the infants in the EIG group had received solids by 4 months. This may have actually decreased any effect the authors found.


What does this all mean?
This appears to be the first randomized study looking at whether babies sleep better when they get solids earlier than 6 months. The results are convincing but not overwhelming (7 minutes), although they may have been blunted a bit by the fact that parents in both groups had introduced solids by 6 months. Based on this one study, I am not planning to change my practice yet, but I will be on the look-out for additional data.

Perkin MR, Bahnson HT, Logan K, et al. Association of Early Introduction of Solids With Infant SleepA Secondary Analysis of a Randomized Clinical Trial. JAMA Pediatr. Published online July 09, 2018. doi:10.1001/jamapediatrics.2018.0739