The Wall Street Journal examines several studies that show the impact of sleep interruptions on sleep quality, mood, and cognitive performance.

In a study published in 2014 in the journal Psychology and Aging, Kristine Wilckens, an assistant professor of psychiatry at the University of Pittsburgh School of Medicine and co-researchers had 59 young adults and 53 older adults wear accelerometers on their arms that measured whether they were sleeping or not over the course of a week.

The researchers found in both groups that when individuals didn’t have continuous sleep, they performed worse on a series of tests that measured cognitive function, such as memory recall and verbal fluency. The total sleep time, however, didn’t have an impact on cognitive performance of older individuals in the group.

“The question that we ended up having is, ‘OK does this mean that older adults need less sleep but they need it to be continuous, they need it to be consolidated?’ ” said Dr. Wilckens.

A study published last year in the journal Sleep Medicine found that even one night of fragmented sleep negatively impacts mood, attention span and cognitive ability to the same degree as restricting sleep to four hours in a night.

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