Woke up at the wrong side of the bed? You might want to blame your interrupted sleep.
In a new sleep study conducted by a group of researchers from Johns Hopkins Medicine, people who had a couple of forced awakenings tend to have fouler moods than those who had delayed bedtimes or shorter but uninterrupted sleep.
For the study, the team worked with more than 60 men and women who were physically fit to undergo an experiment. They were placed in three different sleeping conditions, namely, uninterrupted sleep, delayed bedtimes, and forced awakenings. All of them then answered a questionnaire before going to bed to measure their mood throughout the day.
During the first night, those who belonged to forced awakenings and delayed bedtimes both registered a higher negative mood. However, on the second night, there's a marked difference between the two. While the mood of delayed-bedtimes participants declined by 12%, those who had interrupted sleep plummeted by as high as 31% when compared to the first night. Their positive mood continued to go down by the third night.
One of the possible explanations for the vast difference is the inability of people with forced awakenings to reach the slow-wave sleep phase. Also known as the deep sleep, which is composed of three stages of NREM (non-rapid eye movement). This stage is essential for human survival since it's largely responsible for the restoration of both mind and body so they're both prepared for the next day.
The team went on further to investigate the link between depression and insomnia, a common sleeping disorder. Employing an examination known as polysomnography, they discovered that people with insomnia had shorter periods of deep sleep, which affect their positive mood, thereby reducing it. It also brings down energy levels and affects their ability to be friendly and sympathetic.
The study is now available in journal Sleep.