Interrupted sleep may be just as detrimental as no sleep, according to a recent study.

Researchers from Tel Aviv University found a causal link between interrupted sleep patterns and compromised cognitive abilities, shortened attention spans, and negative moods. They also discovered that interrupted sleep is equivalent to no more than four consecutive hours of sleep.

Interrupted sleep - which includes familiar cry in the night, followed by a blind shuffle to the crib, a feeding, a diaper change, and a final retreat back into oblivion - is the sleep pattern of most new parents.

"The sleep of many parents is often disrupted by external sources such as a crying baby demanding care during the night. Doctors on call, who may receive several phone calls a night, also experience disruptions," researcher Avi Sadeh said in a statement. "These night wakings could be relatively short -- only five to ten 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."

For the study, researchers monitored the sleep patterns of student volunteers at Tel Aviv University's School of Psychological Sciences. Their sleep patterns were monitored at home using wristwatch-like devices that detected when they were asleep and when they were awake. The students slept a normal eight-hour night, then experienced a night in which they were awakened four times by phone calls and told to complete a short computer task before going back to sleep after 10 to 15 minutes of wakefulness.

Researchers said the study showed a direct link between compromised attention, negative mood, and disrupted sleep -- after only one night of frequent interruptions.

"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 ten times a night for months on end -- pay for common infant sleep disturbance is enormous."

Sadeh added that previous studies on sleep patterns in the last 50 years have focused on sleep deprivation, and practically ignored the impact of night-wakings, which is a pervasive phenomenon for people from many walks of life.

"I hope that our study will bring this to the attention of scientists and clinicians, who should recognize the price paid by individuals who have to endure frequent night-wakings," he said.

The findings were recently published in the journal Sleep Medicine.