Most adults need seven to nine hours of uninterrupted sleep at night. Researchers have now revealed that sleep interruptions are worse for the mood than overall reduced amount of sleep.
For the study, participants were subjected to eight forced awakenings. The researchers found that they showed similar low positive mood and high negative mood after the first night as compared to those with delayed bedtimes. The study participants were asked to rate how strongly they felt a variety of positive and negative emotions, such as cheerfulness or anger.
The researchers stated that significant differences emerged after the second night. The forced awakening group had a reduction of 31% in positive mood, while the delayed bedtime group had a decline of 12% compared to the first day. The team did not find significant differences in negative mood between the two groups on any of the three days, which suggested that sleep fragmentation was especially detrimental to positive mood.
Lead author Patrick Finan Johns Hopkins University School of Medicine said, "When your sleep was 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 was key to the feeling of restoration."
Researchers also found that the forced awakening group had shorter periods of deep, slow-wave sleep and that interrupted sleep affected different domains of positive mood; it reduced not only energy levels, but also feelings of sympathy and friendliness.
The study is published in Sleep.