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How did you sleep last night? Your reaction may vary depending on how long you were in bed, how long you turned over, and whether you felt rested. However, it may also depend on whether you exercised today, the messages on your wearable device, or even when you were asked.
This article is part of a special series exploring important questions about sleep. Click here for details.
“Everyone has their own definition of sleep quality, and that’s the problem,” said Nicole Tan, a sleep researcher at the University of Warwick in the UK.
While sleep quality and what defines it is still a mystery that scientists are still trying to figure out, a good night’s rest involves a series of sleep cycles, or distinct sequences of stages of brain activity that you experience during sleep. We know that (see the image below). And for most of us, each stage of these cycles is necessary to wake up feeling refreshed. The average person experiences four to five complete menstrual cycles per night, and any disruption to this can have negative effects on your health in both the short and long term.
“Poor sleep quality is associated with a number of negative physical health outcomes,” says Jean-Philippe Chape of the University of Ottawa in Canada. Similar to what you might expect from not getting enough sleep (see Why your chronotype is key to knowing how much sleep you need), these include cardiovascular disease, stroke, high blood pressure, Type diabetes and increased risk of weight gain.
Although there is no clear consensus on what defines sleep quality, researchers and doctors often analyze sleep using electroencephalograms (EEGs), which track brain activity during sleep.
