Sleep is one of the most important elements of healthy living, enabling us to function and perform at our absolute best, and experience a greater overall quality of life. This has been shown consistently across decades of research. This consistent finding often leads to another question though – do the findings hold true for naps? Do mid-day naps add to the benefits of sleep, or do they ultimately do more harm than good?
Answering this question requires us to first consider how sleep is regulated. Sleep regulation, or when we sleep and how much we sleep, is controlled by two processes:
- Process S, a homeostatic system that balances wakefulness and energy expenditure with sleep and rest.
- Process C, a circadian system that acts like our body clock, telling cells and tissues what to do when, based on the time of day.
Process S is linear, insofar as that as the amount of time we are awake increases, the more our desire to sleep (also known as ‘sleep pressure’) also increases. Process C, on the other hand, is non-linear because throughout the day its drive to make us sleep peaks and troughs at different times. We have two main stages of sleep, NREM and REM, and it is thought that process S regulates NREM as it is energy sparing, while process C regulates REM where the majority of sleep brain activity takes place.
The question is, therefore, where do naps fit into this equation? If our bodies already have mechanisms in place to regulate traditional sleep, do they also regulate naps, or are there different mechanisms in place here?
The answer, predictably, depends entirely on the circumstances. Carving out time for a midday nap can act as a recovery boost, allowing you to function more effectively post-nap. The reason for this is that being awake causes fatigue over time, which in turn diminishes cognitive and physiological functioning. In other words, as we use more and more energy to remain awake, our bodies try to promote sleep and recovery to prevent our energy levels depleting. Our bodies have entire systems dedicated to preventing us from running out of energy completely, in fact. They act as a survival mechanism, slowing the rate at which we use energy – reducing our brain power and overall motivation to move.
Naps have been shown to support continued effective functioning throughout the day, but there’s a catch. The size of the effect napping has depends entirely on the need for sleep when the nap is had – i.e. a nap is more beneficial for someone who has underslept, and less beneficial for those that have slept normally.
Evidence suggests that naps are successful in effectively reducing the typical markers of sleep pressure (slow brain wave activity). They can actually be so effective as to disrupt nighttime sleep later on. Even short naps can offset a lack of sleep in some cases. That said, we would not recommend napping as an essential part of getting enough sleep – it is only to be used when absolutely necessary.
Other evidence has shown that naps can effectively reduce both objective and subjective indicators of sleepiness, as gauged by questionnaires and tests of attentional awareness. Naps can improve cognitive performance, memory consolidation and subsequent learning. With respect to cognitive performance specifically, it is believed that this may result from increased alertness and reduced sleep pressure, rather than a direct effect per se – after all, it is feasible that individuals would perform better mentally if they are alert and awake.
How long should I nap for?
A question commonly asked because of the varying impact that napping has – some people tend to feel tired and groggy post-nap, while others feel refreshed. There are a host of factors that explain this, not least the amount of sleep someone is getting on a regular basis outside of the nap.
Ultrashort naps (roughly 10 minutes long) include primarily early NREM stages, whereas longer naps start to include deeper stages of sleep. Research suggests that naps that only include NREM sleep leave us feeling more alert immediately afterwards, and avoid any groggy feelings entirely. Longer naps, however, will leave us feeling groggy for a short period afterwards.
A study investigating the effects of different nap lengths (5, 10, 20 and 30 minutes) found a 10 minute nap to be the sweet spot that increased post-nap alertness to a greater extent than a nap of any other length. On the other hand, although longer naps bring with them an immediate (but short-lived) groggy feeling, they may ultimately provide longer-lasting benefits. Studies have shown that once the grogginess dissipates, sleepiness is reduced to the extent it would have been if a shorter nap had occurred – and that this reduction will last for an extended period of time (unlike with shorter naps).
In summary, a short daily nap (of between 5 and 30 minutes) can be an excellent strategy to help you continue to function at a high level throughout the day, as well as to support the brain processes that aid learning, memory storage and overall cognitive functioning. This is true even if we are habitually getting adequate sleep.