Sleeping is a vital need, because our body and our brain must be able to replenish energies and reorganize all the information we have accumulated during the day, as well as contribute to the process of growth and the regulation of biological rhythms. Experts recommend between seven and eight hours of sleep a day .

Less than that, as we all know, can take its toll: we find it hard to concentrate, we are more labile and irritable and our health can suffer by reducing the functioning of our immune system, among other things.

But… what happens when we oversleep? Is it bad to sleep too much? Throughout this article we will try to answer this question.

The importance of sleep

Each and every one of us sleeps, and sleep is an essential biological necessity linked to survival. It is a process through which our nervous system is reorganized and used to restore itself from the damage and the typical activity of wakefulness. It is also associated with the growth and evolution of the nervous system, as well as the consolidation of useful and relevant memories.

They are all phenomena necessary for life , in fact in a literal way: total sleep deprivation for long enough can even lead to death.

Sleep is not something watertight and homogeneous but consists of various phases, specifically four phases of slow sleep (the first being drowsiness, the second superficial sleep, the third medium sleep and finally phase four of deep sleep) and one of REM or paradoxical sleep . These phases follow each other throughout a cycle that is repeated continuously throughout the night, modifying the type of brain waves that we use and each phase having different characteristics.

Interrupting this process or not carrying it out sufficiently so that we do not get what we should (about seven or eight hours a day in adults), whether it is voluntary (for example due to social needs) or involuntary (as in insomnia), may result in the body and mind not resting and repairing itself sufficiently, which may lead to disorders such as increased drowsiness, difficulty concentrating, fatigue and mood and hormonal disturbances .

Sleeping too much: negative effects and risks

Sleep is, as we have indicated, a basic need. And with this in mind, when we talk about sleeping more than usual, most people would consider this to be something beneficial that allows for more and better rest. However, the truth is that as well as not sleeping, sleeping a lot (more than nine or ten hours a day) has also been linked to the appearance of different problems or an increase in the risk of suffering from them.

In short, and although it is not usual, you can sleep too much, enough that it is not healthy : sleeping a lot is bad for us. Among the different risks of sleeping more than nine or ten hours a day, we find the following

1. Alters cognitive ability

It has been observed that, just as when we sleep too little, excessive sleep seems to reduce our cognitive capacity, with an inverted U-shaped pattern being observed in which sleeping too much or too little generates deficits in different mental capacities. Among others, seems to especially affect reasoning and verbal capacity , with a possible effect on short-term memory not being so evident.

2. Ages the brain and may promote mental decline

It has been observed that sleeping too much contributes to the aging of the brain, and there is evidence of a relationship between excessive sleep and cognitive decline, the latter being favored.

In this sense, it has been observed in different studies that people who chronically sleep too much tend to suffer some deterioration of their mental and cognitive functions. It also results in a risk factor for the development of some dementias .

3. Generates more drowsiness and “hangover”

Many people will have noticed that after an excessively long night of sleep they wake up slightly confused, in fact as if they had slept less than usual. And the truth is that sleeping too much tends to generate even more drowsiness, something called a sleep hangover .

Not only that, but it is also common for us to feel dizzy, weak, and have a headache. The exact reason is unknown, although some proposals may be the fact that this causes us to have a worse quality and more superficial sleep, and that we wake up in one of the phases when we should be in deep sleep.

4. Increases the probability of stroke

Although there are doubts as to why, it has been observed that those people who throughout their lives tend to sleep more than nine or more hours a day have an increased risk of suffering from some type of stroke. Specifically, it has been calculated that there is up to 46% more probability of suffering from them than people with a normative amount of sleep . Likewise, it should be taken into account that excessive sleep may not be the cause of the increased probability, but rather a prodrome or sign that something may be going wrong at the vascular level.

5. Facilitates the appearance of metabolic and endocrine disorders

Another aspect that can be affected by excessive sleep is the metabolism and the endocrine system, favouring the appearance of problems such as type 2 diabetes, at least in men. Also obesity.

6. Increases the likelihood of depression

Mood can also be altered by poor or excessive sleep. It has been observed that chronic over-sleeping is associated with a higher probability of suffering from depression . It is also the other way around: depression favours inactivity, drowsiness and fatigue that can lead to the subject sleeping more during the day.

7. Poorer general health and shorter life expectancy

Finally, it has been observed that in general people who sleep excessively have a worse health status and life prognosis compared to those who sleep seven to eight hours a day.

Bibliographic references:

  • Bergland, C. (2018). Does Too Much Sleep Have Negative Repercussions? Psychology Today. [Online]. Available at: https://www.psychologytoday.com/us/blog/the-athletes-way/201810/does-too-much-sleep-have-negative-repercussions.

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  • Wild, C.J.; Nichols, E.S.: Battista, M.E.;Stojanoski, B. & Owen, A.M. (2018). Dissociable Effects of Self-Reported Daily Sleep Duration on High-Level Cognitive Abilities. SLEEP, 182.
  • Leng, Y.; Cappuccio, F.P.; Wainwright, N.W.; Surtees, P.G.; Luben, R.; Brayne, C & Khaw, K.T. (2015). Sleep duration and risk of fatal and nonfatal stroke: A prospective study and meta-analysis. Neurology; 25.
  • Spira, A.P.; Chen-Edinboro, L.P.; Wu, M.N. & Yaffe, K. (2015). Impact of Sleep on the Risk of Cognitive Decline and Dementia. Curr. Opin. Psychiatry, 27 (6): 478-483.