At the centre of health and wellbeing is good sleep. We need sleep to rejuvenate our bodies, to boost our immune system, and to consolidate short-term memories into long-term ones. We need it for the release of human growth hormone and for the brain to clear out harmful toxins. Without sleep our mood, energy and mental alertness are compromised, which means and we typically can’t function at full speed. 

But just how much sleep do we need – and how much sleep is too much? 

While everyone’s individual sleep needs vary, the majority of adults 18 years and over need between 7 and 9 hours of sleep a night.

Is Excessive Sleep Bad For You?

Most experts agree that more than 9 hours of sleep is excessive – and, in fact, excessive sleep on a regular basis may be detrimental to a person’s health. An analysis of 74 studies, which  involved more than 3 million people, found that sleep outside the parameters of 7-8 hours – both fewer and excessive hours of sleep – is associated with cardiovascular problems and increased risk of death. The greater the deviation from the recommended 7-8 hours’ sleep, the greater the risk.

Diabetes is another concern. While the link between lack of sleep and type 2 diabetes is well established, a recent study by the University of Chicago involving nearly 1000 adults who had prediabetes or newly-diagnosed untreated type 2 diabetes showed that participants who slept more than 8 hours a night on average (or fewer than 5 hours) had poorer blood glucose control than those who slept between 7 and 8 hours.

We know that memory is distorted when we sleep poorly, but the same is also true when you get too much sleep. The Nurses’ Health Study, one of the largest studies into the risk factors for major chronic diseases in women, found that participants who slept 9 hours or more each night (or 5 hours or fewer) performed worse on memory and thinking tasks compared to those who slept 7-8 hours a night.

Too Much Sleep Zaps Your Energy

At the very least, Harvard Medical School reports that too much sleep may zap your energy. That might seem contradictory, but a person’s circadian rhythm is conflicted when excessive sleep is achieved.

Why? Well, our circadian rhythm regulates the timing of when we sleep and when we awaken. The circadian rhythm, in turn, is controlled by the suprachiasmatic nucleus (SCN), a part of the brain that responds to light. When our eyes register light in the morning, it signals to the SCN that it is time to wake up and sets in motion several actions, including a rise in body temperature and the release of hormones, such as cortisol, each of which play a role in making us feel alert. Oversleeping disrupts this process, leading to a feeling of fatigue, much like jetlag.

Oversleeping May Be A Red Flag For Health Problems

Oversleeping may be a red flag for several existing health issues, especially if you do not feel refreshed on awakening. For example, obstructive sleep apnea is a serious disorder where a person stops breathing momentarily on and off throughout sleep. This stoppage of breathing is typically caused because, in deep sleep, the throat’s muscles relax, and for some people this can block their airway. 

Loud snoring may be a sign a person has sleep apnea. Other symptoms include morning headaches, a dry throat in the morning, excessive daytime sleepiness, difficulty concentrating and altered mood. If you suspect you may have sleep apnea, it is advisable to consult a sleep specialist.

Another sleep disorder is narcolepsy, which is characterized by excessive daytime sleepiness and involuntary episodes of falling asleep during the day. It may also cause hallucinations, cataplexy (where strong emotions and laughter cause sudden muscle weakness or paralysis) or sleep paralysis (temporary inability to move or speak when passing through the stages of wakefulness and sleep). These episodes generally last from a few seconds to a few minutes.

A Sign Of Depression?

Oversleeping may also be a sign of depression. An estimated 40 percent of young adults with depression experience oversleeping, while the figure is more like 10 percent for older adults, with a prevalence amongst females.

Regardless as to why you might be oversleeping, keeping the status quo may not be doing your physical or mental health any favours. Spending an excessive amount of time in bed is linked to health risks, so getting the much-touted 7 to 8 hours of sleep a night is sound advice.