Reviewed by Sahil Chopra, MD, and Stacey Gunn, MD.

Research by Savit Malhotra.

In this second article of our napping mini-series, we’ll be taking a look at when napping can become harmful. Specifically, we will discuss the impact that napping has on sleep drive, nighttime sleep, and a loss of sleep consistency. 

Introduction

As we talked about in the last article, napping can be an incredibly useful tool when done correctly. However, like most other things in life, there are limits to how much a person should nap. After some point, napping can become more detrimental to a person’s daily functioning than beneficial. For this reason, it is important to explore when napping can actually become harmful and the impacts it can have on nighttime sleep. In this week’s article, we’ll take a look at these negative effects, such as the impact that naps can have on sleep drive and nighttime sleep overall. We’ll also talk about how “retirement naps” play a role in the loss of sleep consistency among older people. 

Decreasing Sleep Drive

Let’s look at two key factors that play a role in helping a person fall asleep: the neurotransmitter adenosine and a person’s natural circadian rhythm. As we go about our day, our body makes more and more adenosine.[1] As the level of adenosine builds up, adenosine receptors begin to saturate.[2]  As we continue to build up adenosine throughout the day, we begin to feel more tired. It is for this reason that adenosine is often considered to be the sleep drive. However, when we sleep, the adenosine in our body is broken down and thereby clears the receptors.[3] When we wake up again, we feel more energized due to lower adenosine levels in the body. Interestingly, one of the main ways that caffeine works is by blocking adenosine receptors.  

                                                                        The above graph depicts the alignment between adenosine levels (sleep drive) and circadian rhythm (wake drive)

When we take a nap during the day, we are allowing for some of our adenosine levels to clear, no matter how long we sleep for or even at what time.[4] The longer we sleep, the more adenosine we are able to break down, and the further we are able to decrease our sleep drive. For example, a quick 10-minute nap at around 12:00 PM might not have too significant an impact on nighttime sleep. However, a 2-hour nap at 5:00 PM will likely clear a significant amount of adenosine, and due to the nap occurring later in the day, it is highly likely that nighttime sleep will be impacted. Our sleep drive will have decreased, and our body may not be able to recoup that drive for a few hours. 

Impact on Nighttime Sleep

As we briefly mentioned earlier, the second major determinant of when a person falls asleep is their circadian rhythm (a more detailed explanation of our circadian rhythm is given in our article about melatonin). In the image above, our circadian rhythm fluctuates during the day with some periods of a high wake drive, others of a low wake drive, and everything in between. When we align our sleep with the dips in our wake drive, we are able to fall asleep. The same is true with naps. There is a natural decrease in our sleep drive, typically during the hours of 1:00 PM and 3:00 PM, known as the “circadian dip.” Taking a nap between these hours aligns closely with our circadian rhythm and therefore disrupts it the least.[5] 

Timing your naps against your circadian rhythm, or taking naps that are too long can negatively affect our nighttime rest.[6] This is especially true for those who are struggling with insomnia. In a recent study published in Sleep, it was found that certain napping patterns did in fact indicate a development in insomnia symptoms.[7] Typically, those struggling with insomnia fall into a bad cycle of poor sleep. As a result, they often rely on naps to try and get through the day, which decreases their sleep drive and only worsens their nighttime sleep, making their insomnia worse. 

“Retirement Naps”

Oftentimes, when people retire, they think that they can do whatever it is they want to do, including taking naps whenever they feel like it and for however long they want. “Retirement naps,” while not an official term, is what we will be using to describe these types of naps. The issue with taking naps that have no limits is that it combines all of the issues that we previously discussed. With a decreased sleep drive and a mistimed circadian rhythm, it is not uncommon for a person to experience severely dysfunctional sleep. As a result, their dysfunctional sleep can cause a loss of sleep consistently, which can ultimately lead to insomnia.[8]

Conclusion

Although we spent this article discussing the negative effects of napping, that is not to say that all napping is bad. Instead, we want to highlight to our readers the science behind when napping can do more harm than good. We hope that, by doing this, we can emphasize what not to do when it comes to taking naps so that our readers can make better, and more informed, choices in regards to their sleep. In our next article, we’ll be taking a closer look at nap dependence and what can cause people to become reliant on naps. 

References

  1. Brandon Peters, MD. “How Adenosine Helps You Get a Good Night’s Sleep.” Verywell Health, Verywell Health, 25 Feb. 2025, www.verywellhealth.com/adenosine-and-sleep-3015337.
  2. Porkka-Heiskanen, Tarja, et al. “Adenosine and sleep.” Sleep Medicine Reviews, vol. 6, no. 4, July 2002, pp. 321–332, https://doi.org/10.1053/smrv.2001.0201.
  3. Bryan, Lucy. “Adenosine and Sleep: Understanding Your Sleep Drive.” Sleep Foundation, 14 Dec. 2023, www.sleepfoundation.org/how-sleep-works/adenosine-and-sleep#how-adenosine-affects-sleep.
  4. Bhushan, Dr Devika. “Let’s Sleep Better - to Nap or Not to Nap?” Spread the Light with Dr Devika B, Spread the Light with Dr Devika B, 30 Oct. 2023, askdrdevikab.substack.com/p/lets-sleep-better-to-nap-or-not-to.
  5. Summer, Jay Vera. “Does Napping Impact Your Sleep at Night?” Sleep Foundation, 2 Feb. 2024, www.sleepfoundation.org/how-sleep-works/does-napping-impact-sleep-at-night#:~:text=Many%20people%20naturally%20experience%20a,ability%2C%20and%20improve%20physical%20ability.
  6. “The Lowdown on Naps: Are They More Healthy or Harmful?: Jefferson Health.” Jefferson Health - Greater Philadelphia & South Jersey Region, 6 Aug. 2021, www.jeffersonhealth.org/your-health/living-well/the-lowdown-on-naps-are-they-more-healthy-or-harmful#:~:text=Roszkowski:%20%E2%80%9CNaps%20can%20disrupt%20your,turns%20into%20an%20endless%20cycle.%E2%80%9D.
  7. Pereira, Rui, et al. “323 is daytime napping a risk factor for persistent insomnia symptoms?” Sleep, vol. 44, no. Supplement_2, 1 May 2021, https://doi.org/10.1093/sleep/zsab072.322.
  8. Suni, Eric. “What Causes Insomnia?” Sleep Foundation, 16 Jan. 2024, www.sleepfoundation.org/insomnia/what-causes-insomnia. 

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