Sleep interruptions spoil a person’s positive mood, research reveals

A new study suggests that waking up several times throughout the night is more detrimental to people’s positive moods than when they get an uninterrupted but less sleep.

Researchers at Johns Hopkins Medicine in the U.S. pointed out that the quality of sleep may be more important than quantity, based on their study's findings which can be found in the journal Sleep. The study also explains the link between depressed mood and insomnia, the authors noted.

For the study, the team randomly subjected 62 healthy men and women to three sleep experimental conditions: three consecutive nights of forced awakenings, delayed bedtimes or uninterrupted sleep. The participants underwent a standard mood assessment before bedtimes the following night to measure how strongly they felt a variety of positive and negative emotions, such as cheerfulness and anger.

After the trial, the researchers found that participants who were subjected to eight forced awakenings and those with delayed bedtimes showed similar low positive mood and high negative mood after the first night. The team noted significant differences after the second night, when the forced awakening group showed a reduction of 31 percent in positive mood, while the delayed bedtime group had a decline of 12 percent.

The team also used a test called polysomnography to monitor certain brain and body functions while the subjects were sleeping to assess sleep stages. The forced awakening group was observed to have shorter periods of deep slow-wave sleep compared with the delayed bedtime group.

The lack of sufficient slow-wave sleep had a statistically significant association with the subjects’ reduction in positive mood, the researchers said. They also found that those who experienced interrupted sleep have reduced energy levels as well as lessened feelings of sympathy and friendliness.

The findings also suggest that the effects of interrupted sleep on positive mood can be cumulative, according to Patrick Finan, the study's lead author and an assistant professor of Psychiatry and Behavioural Sciences at the university’s School of Medicine. This is because the groups’ mood differences were observed after the second night and continued the day after the third night of the study.

“When your sleep is disrupted throughout the night, you don't have the opportunity to progress through the sleep stages to get the amount of slow-wave sleep that is key to the feeling of restoration,” he said.

Frequent awakenings throughout the night are common among new parents and on-call health care workers, Finan noted. It is also one of the most common symptoms among people with insomnia, who make up an estimated 13 to 33 percent of the Australian adult population, according to the Medical Journal of Australia.

Finan said that further studies are needed to learn more about sleep stages in people with insomnia and the role played by a night of recovering sleep.

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