According to Tasnim news agency, as reported in the November 1 issue of the journal Sleep, Johns Hopkins Medicine researchers studied 62 healthy men and women randomly subjected to three sleep experimental conditions in an inpatient clinical research suite: three consecutive nights of either forced awakenings, delayed bedtimes or uninterrupted sleep.
Participants subjected to eight forced awakenings and those with delayed bedtimes showed similar low positive mood and high negative mood after the first night, as measured by a standard mood assessment questionnaire administered before bedtimes. Participants were asked to rate how strongly they felt a variety of positive and negative emotions, such as cheerfulness or anger.
But the researchers say significant differences emerged after the second night: The forced awakening group had a reduction of 31 percent in positive mood, while the delayed bedtime group had a decline of 12 percent compared to the first day. Researchers add they did not find significant differences in negative mood between the two groups on any of the three days, which suggests that sleep fragmentation is especially detrimental to positive mood.
Study lead author Patrick Finan, Ph.D., an assistant professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine said "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."
Although the study was conducted on healthy subjects with generally normal sleep experiences, Finan says the results are likely to apply to those who suffer from insomnia.