A broken slumber is as bad as getting four hours' sleep
It will come as no surprise to new parents struggling after a night of feeds, or to doctors on call, but being woken up briefly during an otherwise normal night of sleep is as detrimental as sleeping for just four hours.
Researchers discovered that being woken from a deep slumber by a crying baby or an emergency call causes the same confusion, depression and fatigue as being severely sleep-deprived.
It means that even when people get a total of seven hours sleep a night, having that sleep regularly interrupted will leave them feeling as if they have slept for barely half that time.
Researchers at Tel Aviv University warned that such interruptions were likely to leave parents feeling bewildered, dejected and exhausted.
They could have a detrimental effect on on-call professionals, including doctors or firemen, impacting upon their attention span and ability to make decisions.
"The sleep of many parents is often disrupted by external sources such as a crying baby demanding care during the night," said Prof Avi Sadeh.
"Doctors on call, who may receive several phone calls a night, also experience disruptions. These night wakings could be relatively short – only five to 10 minutes – but they disrupt the natural sleep rhythm."
The team studied 61 adults who were monitored at home using wristwatch-like devices that detected when they were asleep and awake.
The volunteers slept a normal eight-hour night, then experienced a night in which they were woken four times by phone calls every 90 minutes and not allowed to go back to sleep for 15 minutes.
The students were asked each following morning to complete computer tasks to assess alertness and attention, as well as to fill out questionnaires to determine their mood.
The experiment showed a direct link between disrupted sleep and poor attention spans and negative mood after only one night of frequent interruptions. The volunteers were found, on average, to be 24pc more confused, 29pc more depressed and 43pc more fatigued after broken sleep.
A second experiment in which volunteers were allowed to sleep for only four hours, showed similar results, suggesting regular night disruption has the same impact as getting only half the recommend eight hours of sleep. (© Daily Telegraph, London)