“It’s not rocket science,” says Russell Foster, explaining how most of us are deprived of sleep and in need of an early night. No, but it is neuroscience — and as Professor of Circadian Neuroscience at Oxford University, he should know.
Foster is one of the U.K.’s leading experts on sleep, and an evangelical advocate of us all getting eight undisturbed hours each night, not just to improve our physical well being but our mental health, too.
Along with a group of other experts at Cambridge, Harvard and Surrey universities, he has put together a report on sleep and our body clocks, and one of his main conclusions is striking.
“We are the supremely arrogant species; we feel we can abandon four billion years of evolution and ignore the fact that we have evolved under a light-dark cycle,” he told the BBC.
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 and 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 Professor 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 impact of such night wakings on an individual’s daytime alertness, mood, and cognitive abilities had never been studied. Our study is the first to demonstrate seriously deleterious cognitive and emotional effects.”
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.
Disrupted sleepers were found, on average, to be 24% more confused, 29% more depressed and 43% more fatigued
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 24% more confused, 29% more depressed and 43% 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.
“Our study shows the impact of only one disrupted night,” Sadeh said.
“But we know that these effects accumulate and therefore the functional price new parents — who awaken three to 10 times a night for months on end — pay for common infant sleep disturbance is enormous.
‘Besides the physical effects of interrupted sleep, parents often develop feelings of anger’
“Besides the physical effects of interrupted sleep, parents often develop feelings of anger toward their infants and then feel guilty about these negative feelings.”
Sadeh is currently researching interventions for infant sleep disturbances to reduce the detrimental effects of disrupted sleep on parents.
The team also hopes the findings will encourage employers to reassess shift work and staff being placed on call.
Michal Kahn, a co-author of the report, added: “Our findings bear relevance to substantial portions of the population whose sleep is regularly fragmented, including medical students, shift workers, military personnel and parents.
“Professionals as well as the general public should be aware of the detrimental effects of the various kinds of disruption in sleep on daily functioning and mood and consider countermeasures to minimize their consequences.
The study was published in the journal Sleep Medicine.