When "quiet" isn't quiet enough: how shallow sleep in infants may relate to autism
Peer reviewed – experimental study - humans
Babies with an increased likelihood of autism may struggle to settle into deep, restorative sleep, according to a new study from the University of East Anglia.
Researchers studied the link between sleep and sensory sensitivity, which is common in neurodivergent infants.
They found that when babies with this trait napped in a noisy environment, their deep sleep was considerably disrupted.
But even in a quiet room, those with high sensory sensitivity still slept more lightly - suggesting that both their unique sensory wiring and their surroundings influence how well they rest.
The work reveals important clues about why some babies, especially those who are highly sensitive to sensory input, are more likely to struggle to achieve restorative sleep.
Prof Teodora Gliga, from UEA's School of Psychology, who led the study, said: "Many parents tell us their baby seems 'easily bothered' by sounds or sensations and we are now beginning to see how that sensitivity can affect their sleep.
"By monitoring babies' brainwaves, we could see clear differences in how deeply infants slept in response to sound.
"More sensitive infants didn't spend less time in deep sleep - their deep sleep was simply shallower. The slow waves that define this stage were smaller and weaker, showing that while the duration was similar, the depth and quality of their sleep were reduced.
"Our results show that even everyday sounds can make it harder for some babies to stay in deep sleep, especially those with naturally heightened sensory responses."
Some babies in the study were at higher likelihood of developing autism, not because they show diagnosable features at such a young age, but because they have an older autistic sibling.
How the research happened
Dr Anna de Laet, first author on the study, and now at King's College London, said: "Autism is a highly heritable condition. We included infants both with and without an older autistic sibling to capture a wide range of sensory sensitivities, which are common in autism and emerge early in development, often well before a diagnosis is possible.
"These sensitivity traits don't mean a baby will develop autism, which we can't diagnose reliably before the age of three, but they help us study how early sensory differences might shape sleep in infancy."
To understand these patterns, families visited the UEA sleep lab, where each baby completed two naps - one in a quiet room and one in a room where gentle beeps, about as loud as a normal conversation, were played every few seconds.
Researchers recorded babies' brain activity during sleep and compared sleep depth between the two conditions.
Parents also completed questionnaires about their baby's typical behaviours and sensory sensitivities, which could be linked to their sleep quality.
A total of 41 babies between eight and 11 months contributed to the data for the final analysis.
Good sleep 'vital' for brain development
Prof Gliga said: "Reducing noise may help particularly sensitive babies, but it's not enough on its own. Their sleep was still shallower in quiet environments.
"Good sleep is vital for brain development and emotional well‑being, so understanding these differences is key to providing better support for families."
The authors highlight the need for further research into how deep sleep might be better supported in these infants, potentially by strengthening the brain's ability to filter sensory input during sleep.
This study was funded by Wellcome.
'Sound asleep: Sensory decoupling during sleep depends on an infant's sensory profile' is published in the journal Sleep.
Additional collaborators: Prof Rachael Bedford, Queen Mary University of London and Dr Alpar Lazar, UEA.
