Research increases understanding of how sleep is regulated differently in babies

UCL researchers have discovered how sleep is regulated differently in babies compared to adults.

A team led by UCL’s Dr Kimberley Whitehead has found that infants have much longer periods of ‘active’ sleep – a lighter form of sleep.

Researchers said these long durations of active sleep suggest differences in the underlying ‘brain circuitry’ that controls sleep patterns.

Active sleep is one of four sleep-wake states. It is characterised by closed eyes with intermittent rapid eye movement, isolated facial and body movements and brief vocalisations The other three are wakefulness, quiet sleep (a deeper form of sleep characterised by almost complete stillness) and transitional sleep.

The study team monitored sleep-wake states in 175 pre-term babies using electroencephalography (EEG) to measure brain activity, heart rate and breathing measurements, and cot side behavioural monitoring. Babies were born between 2015 and 2019 at the Elizabeth Garrett Anderson wing of UCLH.

The study found pre-term babies spent as much as 97% of their time asleep, but that as infants grow older the time spent in active sleep declined although the duration of quiet sleep increased.

Researchers also found that younger infants were less likely to be woken by disturbances to their sleep – for example by blood tests.

Researchers suggested that disturbing infants’ active sleep could have a negative impact, and said it should be avoided where possible. They said in future hospital staff may be able to continually monitor sleep-wake states in infants to determine the best time to carry out procedures.

Dr Whitehead said: “As every parent knows, babies spend much of their time asleep, but we now have a better understanding of why this is – infants are in some way ‘wired’ to prioritise periods of active sleep. This helps explain why babies – while they sleep a lot – are also prone to wake up at regular intervals, as more of their sleep is in this active, lighter phase.

“Our findings have practical implications for wards. We hope in future to research whether it may be helpful for hospital staff to monitor sleep-wake states of babies to avoid disturbing them when they are in periods of active sleep. We also think measures to reduce disturbances may promote sleep in infants.”