In a first of its kind study, researchers at Tel Aviv University's School of Psychological Sciences established a causal link between interrupted sleep and compromised cognition, attention span and humor, concluding that interrupted sleep is roughly equivalent to four hours of consecutive sleep.
According to study author Dr. Avi Sadeh, who directs a sleep clinic at TAU, previous studies have established an association between night waking and the aforementioned negative consequences, but his is the first to establish a causal link.
The sleep patterns of 61 healthy adults, 40 of which were females between the ages of 20 and 29 years old, were traced at their homes using actigraphy and sleep diaries.
Self-reporting was the method used to assess mood and participants were asked to perform computer tasks to assess cognitive abilities and attention span.
Participants were assessed after both a normal (control) night's sleep and after a night during which sleep was either restricted to four hours or interrupted four times over the course of eight hours in bed.
Interruptions were designed to keep participants awake for a period of 10 to 15 minutes.
While researchers found few significant differences between interrupted sleep and sleep deprivation, the differences between the aforementioned conditions and a normal night's sleep were vast.
Results indicate an increase in depression, fatigue and confusion in addition to diminished vigor and motivation when sleep is interrupted or restricted.
"Our study shows the impact of only one disrupted night," says Dr. Sadeh. "But we know that these effects accumulate and therefore the functional price new parents -- who awaken three to ten times a night for months on end -- pay for common infant sleep disturbance is enormous."
Dr. Sadeh is already at work on further research on how to reduce the negative consequences of night wakings for parents of infants.
In an interview, he added that sleep research has been largely concentrated on the deprivation side over the past 50 years and not enough has been done to examine the effects of sleep interruption.
His study was published in the journal Sleep Medicine.