I’ve heard that light sleep is “junk sleep” and that I should be focusing on deep sleep and REM sleep. Is this true? Does light sleep have any benefits?
All the stages of sleep are important to physical health and well-being. In discussions of sleep, there is a great emphasis placed on the phases of deep sleep and REM sleep, so much so that it can be easy to overlook the value of light sleep. However, light sleep may be just as important as other sleep stages to feeling energized, alert, and focused during the day.
The stages of sleep
Sleep scientists study the progression of sleep through different stages, and in a series of cycles that make up what’s known as “sleep architecture”. There are two primary types of sleep: REM sleep and Non-REM sleep, which is often referred to as NREM. Non-REM sleep itself is comprised of several stages: Stage 1, Stage 2, and Stage 3. Stages 1 and 2 of NREM sleep are considered “light sleep,” while Stage 3 is “deep sleep.” So, when we talk about light sleep we’re talking about stages 1 and 2. Stage 1 of light sleep is the lightest sleep stage, and phases of stage 1 sleep are often quite brief. Stage 2 sleep, on the other hand, makes up roughly half of a typical night of sleep.
Stage 2: light, but significant
Stage 2 is where a lot of the action happens, including significant changes to brain activity. One of the most important elements of Stage 2 sleep is the emergence of sleep spindles, bursts of electrical activity in the brain that are believed to play an important role in maintaining the brain’s communication system, as well as in brain functions related to learning and memory. In research, sleep spindles have been associated withsynaptic plasticity, memory consolidation, and improvements in declarative memory formation. Sleep spindle density has even been associated with IQ.
Dynamics of our sleep cycle
The line between light sleep and deep sleep is very fluid. The stages of NREM sleep, light and deep, are much more similar to each other than they are to either REM sleep or a state of full wakefulness. It is actually possible to get a “deeper” light sleep that is very similar to deep sleep, and may even have the same effects as deep sleep. This is especially true in older adults. As we age, the distribution of our nightly sleep among phases changes. Older adults tend to spend less time in what sleep scientists classify as deep sleep and more time in light sleep. But with the help of strong sleep habits, older adults can still sleep restfully and well in a high quality, “deeper” light sleep. At any age, light sleep matters a great deal.