A good night's sleep is tied to interruptions, not just hours

Good sleep isn't just about how long you sleep. Continuity may be equally important.

Getting up in middle of the night multiple times to soothe a crying baby or go to the bathroom impacts your mood and cognitive abilities the next day, new research has found.

In a study published last month in the journal Sleep, researchers from Johns Hopkins University School of Medicine found that individuals forced to awaken multiple times during the night showed a greater decline in positive mood than those forced to go to bed later. They also had less slow-wave or deep sleep, the third stage of non-rapid eye (NREM) movement sleep.

Research from the University of Pittsburgh has shown that the cognitive performance of elderly individuals was impaired when their sleep was disrupted, but not when they slept a shorter amount of time straight through. And a study done in Israel published last year found that a fragmented night of sleep for a full eight-hours impacted mood and attention as much as sleeping just four hours a night.

The recent Sleep study included healthy individuals without any diagnosed sleep problems. The 62 subjects were brought into the lab and randomized into three groups: a group whose sleep was repeatedly disrupted; a group whose bedtime was delayed; and a control group, said Patrick H. Finan, an assistant professor in the department of psychiatry and behavioral sciences at Johns Hopkins and lead author of the study.

The subjects were given eight hours to sleep in the lab for three consecutive nights.

Those in the disrupted group were awakened each hour for 20 minutes for seven of the eight hours. They were woken up for a full hour for the eighth hour, which took place at a different time of night on each of the nights.