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Have you ever experienced feeling sleepy even after getting enough sleep, finding it hard to wake up in the morning due to lingering fatigue, or lacking motivation despite not being sleep-deprived?
This article explains the causes of oversleeping, related illnesses, and how to improve the situation for those who might be worried that they are ill because they wake up tired even after sleeping a lot, or can't get up even though they haven't had too little sleep.
How much is too much sleep?
"Oversleeping" refers to sleeping more than the body needs when you are in a healthy physical and mental state. While the amount of sleep an individual needs varies depending on age, constitution, and lifestyle, the National Sleep Foundation recommends the following sleep duration guidelines by age group:
| Age | Recommended Sleep Duration |
|---|---|
| Newborns (0–3 months) | 14–17 hours |
| Infants (4–11 months) | 12–15 hours |
| Toddlers (1–4 years) | 11–14 hours |
| Preschoolers (4–6 years) | 10–13 hours |
| School-age Children (6–15 years) | 9–11 hours |
| Youth to Adults (15–64 years) | 7–9 hours |
| Seniors (65+ years) | 7–8 hours |
Both too little and too much sleep can strain your body, so it's important to aim for an appropriate amount of sleep, using the table above as a guide.
Also, oversleeping on holidays can disrupt your body clock, leading to lighter sleep and difficulty falling asleep. On holidays, aim to keep your sleep duration to within two hours of your weekday sleep schedule.
8 Reasons for Oversleeping
Even if you think you've had enough sleep, your sleep environment or lifestyle might be preventing you from getting deep sleep. If you regularly oversleep, it could be that your sleep quality is poor, preventing you from recovering efficiently, which results in longer sleep times.
The main eight reasons that can lead to poor sleep quality and consequently oversleeping are:
- Stress
- Sleep deprivation
- Fatigue
- Genetics (Long sleeper)
- Hormonal factors
- Seasonal factors
- Medication or stimulants
- Irregular lifestyle
Stress
Typically, the sympathetic nervous system is dominant during the day, while the parasympathetic nervous system, which relaxes the body, is dominant during sleep.
In a healthy state, the balance between the sympathetic and parasympathetic nervous systems is maintained. However, stress can cause the sympathetic nervous system to become dominant, disrupting the autonomic nervous system balance, leading to a decline in sleep quality and potentially oversleeping.
Sleep Deprivation
If you don't get enough sleep during busy weekdays, leading to accumulated sleep debt (a state of sleep deprivation), it can cause you to oversleep. Be careful if there is a difference of two hours or more between your weekday and holiday sleep times.
Regarding general sleep duration, the "Sleep Guide for Health Promotion 2023" published by the Ministry of Health, Labour and Welfare states that while appropriate sleep duration varies by individual, it should generally be at least 6 hours.
Furthermore, according to a "Sleep Quotient®" survey conducted by Brain Sleep targeting 10,000 people across 47 prefectures in Japan (allocated by gender, age, and prefecture), the average sleep duration in Japan was 6 hours and 27 minutes in 2020, 6 hours and 43 minutes in 2021, and 6 hours and 48 minutes in 2022, showing an improving trend with sleep duration increasing by 21 minutes over the past two years.
However, the 2023 survey found that the average sleep duration in Japan was 6 hours and 43 minutes, a decrease of 5 minutes compared to 2022, returning to the same sleep duration as 2021.
Fatigue
Normally, getting enough sleep helps recover from physical fatigue, but if fatigue is excessively accumulated, even after sleeping, sluggishness and tiredness may persist, leading to oversleeping. It is important to control your daily life to prevent excessive fatigue accumulation.
Genetics (Long Sleeper)
A long sleeper is someone who naturally needs more sleep. Long sleepers are primarily influenced by genetic factors and are a matter of constitution, distinct from hypersomnia, which is a sleep disorder.
Generally, it refers to individuals who feel sleep-deprived if they don't get at least 9 hours of sleep every day. However, the International Classification of Sleep Disorders, 3rd Edition (ICSD-3), defines a "long sleeper" as an adult sleeping 10 hours or more, or a child sleeping 2 hours or more beyond the age-appropriate duration, so there is no clear definition.
While long sleepers can function normally during the day if they get enough sleep, individuals with hypersomnia experience severe daytime sleepiness even after sufficient nighttime sleep, sometimes succumbing to naps even in situations requiring concentration.
For more detailed information on long sleepers, please refer to the article below:
Am I a long sleeper? Characteristics, causes, diagnosis, and treatment methods.
Hormonal Factors
For women, strong daytime sleepiness can be a symptom of premenstrual syndrome (PMS), which occurs before menstruation.
This is thought to be due to an increase in progesterone (a luteal hormone) before menstruation, which raises basal body temperature and reduces the clear rhythm of daily body temperature. In early pregnancy, the action of progesterone, which aims to rest the body, can also cause increased sleepiness and sluggishness.
Furthermore, after menopause, the decrease in female hormones can lead to lighter and shorter sleep, and this can also cause daytime sleepiness.
Seasonal Factors
According to the "Sleep Guide for Health Promotion 2023" published by the Ministry of Health, Labour and Welfare, "sleep duration also varies by season, being 10 to 40 minutes longer in winter compared to summer."
The main reason is the shortening of day length (the time from sunrise to sunset).
Light stimulation is related to waking up in the morning and resetting the body clock. In winter, when sunrise is later, the time at which light stimulation enters is delayed, so awakening is also thought to be delayed.
Conversely, in summer, not only does light stimulation come earlier (extension of day length), but bedrooms also tend to be hot and humid, making it more difficult to fall asleep and stay asleep than in other seasons.
However, some research indicates that people tend to oversleep in spring, so the causal relationship between day length and sleep duration is not yet fully understood.
Medication and Stimulants
Medications, alcohol, tobacco, coffee, and other stimulants can also affect sleep.
For example, if you are taking sleeping pills or tranquilizers, the effects of the medication may linger upon waking, leading to oversleeping.
Additionally, alcohol, nicotine in tobacco, and caffeine in coffee can reduce sleep quality, so it's important to be mindful of the amount and timing of their consumption.
Irregular Lifestyle
An irregular lifestyle, such as staying up late, lack of exercise, and an unbalanced diet, also contributes to poor sleep quality.
In particular, staying up late and having an irregular lifestyle can disrupt the body clock, leading to irregularities in sleep cycles like REM and non-REM sleep, thereby reducing sleep quality.
To maintain a consistent body clock rhythm, it's important to try to wake up and go to bed at the same time on both weekdays and weekends.
Diseases to Watch Out for When Oversleeping Becomes a Concern
If you feel sleepy even after getting enough sleep and tend to oversleep, it could be due to an underlying illness.
Diseases suspected with oversleeping broadly fall into two categories: those where the brain's sleep-regulating function is impaired, leading to severe daytime sleepiness, such as idiopathic hypersomnia and depression; and those where chronic sleep deprivation occurs due to physical symptoms preventing deep sleep, such as sleep apnea syndrome and restless legs syndrome.
Below, we will introduce the characteristics and symptoms of each disease. If you feel you might be affected, we recommend consulting a clinic.
Idiopathic Hypersomnia
This is a condition where a person experiences excessive daytime sleepiness despite getting sufficient sleep at night. The cause of its onset is still unknown, but a functional abnormality in the brain's sleep-wake regulation is suspected. Individuals often wake up feeling unrefreshed, may frequently doze off due to severe sleepiness, and some may experience symptoms like dizziness, lightheadedness, or headaches.
Depression
A common mental illness where the brain is not functioning properly due to mental or physical stress. While it is a mood disorder, some individuals also experience physical symptoms such as hypersomnia, insomnia, changes in appetite, and general malaise.
In general, the act of sleeping in depression is also referred to as "sleep escape," and it can be said to be a defense mechanism for escaping from severe stress or painful events. Since sleep has a restorative effect on both mind and body, sleeping a lot during depression is not a bad thing.
Sleep Apnea Syndrome (SAS)
This is a condition where the airway (upper airway) narrows during sleep, leading to repeated episodes of apnea (cessation of breathing) or hypopnea (shallow breathing). The repeated episodes of apnea and hypopnea cause both the brain and body to suffer from oxygen deprivation, putting a strain on various organs. Sleep becomes shallow, so even after sleeping for a sufficient amount of time, you may not feel rested.
Restless Legs Syndrome (RLS)
Restless Legs Syndrome (RLS) is also known as Willis-Ekbom disease, characterized by unpleasant sensations primarily in the legs. It is approximately 1.5 times more common in women than in men.
Symptoms include a tingling sensation in the legs, an irresistible urge to move the legs, a feeling of warmth, or a desire to scratch the deep parts of the legs, causing an indescribable discomfort from within the legs that is relieved by moving them.
Symptoms often appear or worsen when trying to sleep in bed at night, leading to difficulty falling asleep or waking up due to leg discomfort during sleep, resulting in sleep deprivation.
While symptoms generally appear or worsen from evening to night, they can also occur when sitting still in places like bullet trains, airplanes, or movie theaters.
Things to Watch Out for and Symptoms of Oversleeping
Oversleeping can sometimes cause headaches and sluggishness.
Sleep-Induced Headache
While there is no medical causal relationship between oversleeping and headaches, migraines or tension-type headaches can occur after oversleeping.
When people sleep for a long time, their blood vessels relax. Furthermore, when in a deep sleep mode, heart rate and respiration decrease, and blood flow slows down. If one wakes up in this state, the body desperately tries to send blood, causing the blood vessels to pulsate strongly. As a result, the trigeminal nerve around the blood vessels is pulled, which is thought to cause migraines. The longer one sleeps, the greater the rebound effect upon waking.
On the other hand, tension-type headaches are headaches believed to be related to physical and mental stress. If you sleep for a long time with poor sleeping posture, such as your head falling off the pillow, or your neck, back, arms, or legs bent, it can put extra strain on your neck and shoulders, leading to tension-type headaches upon waking.
For more details on sleep-induced headaches, please see here:
What causes headaches from oversleeping? Treatment methods and prevention tips by type.
Fatigue (Lethargy)
Oversleeping can cause a hangover-like feeling of lethargy. This is called "sleep drunkenness," but it differs from the damage caused by alcohol. Humans reset their body clock through light stimulation, but oversleeping can confuse the part of the brain that controls the daily cycle, leading to lethargy.
Muscle Pain
If you oversleep and maintain the same posture for a long time, your muscles can stiffen and blood circulation can worsen, leading to muscle pain.
The areas most prone to muscle pain from oversleeping are primarily the shoulders, lower back, and back.
If these areas hurt upon waking, light stretching, a walk, or taking a bath to improve blood circulation may help alleviate the pain.
Weight Gain
Surprisingly, research suggests that both insufficient and excessive sleep duration are linked to weight gain.
A study of 276 adult men and women aged 21 to 64, measuring their body composition and sleep duration, found that groups with short sleep duration (around 5-6 hours) and long sleep duration (around 9-10 hours) had a higher probability of weight gain and a greater risk of obesity compared to the group with moderate sleep duration (around 7-8 hours).
Specifically, the likelihood of gaining 5kg over 6 years was 35% for the short sleep group and 25% for the long sleep group, both higher than the moderate sleep group. The risk of developing obesity also increased by 27% and 21% respectively for these groups.
This suggests that individuals who regularly oversleep are at risk of weight gain and obesity.
Heart and Vascular Diseases
An Oxford University study also found that both insufficient and excessive sleep are linked to an increased risk of mortality from ischemic heart disease such as myocardial infarction and angina, hypertension, and stroke.
The study, which surveyed 61,936 men and 73,749 women with no history of cancer, heart attack, or stroke, found that both men and women who slept too little (under 5 hours) or too much (over 9 hours) had an increased risk of all-cause mortality and cardiovascular disease (CVD) mortality.
This suggests that individuals who sleep, on average, more than 9 hours are at a higher risk of developing heart and vascular diseases such as myocardial infarction and angina.
5 Ways to Improve/Manage Oversleeping
Oversleeping is often linked to sleep deprivation, so aim to get an appropriate amount of sleep and improve its quality. While sufficient sleep duration and quality are the best solutions, if oversleeping persists despite adequate sleep, it could indicate an underlying illness, and you should consult a medical professional.
Relieve Stress
Psychological stress from worries, irritability, or tension activates the sympathetic nervous system, which stimulates the brain. This leads to difficulty falling asleep, light sleep, inability to achieve deep sleep, and overall poor sleep quality.
To avoid accumulating stress, first identify and accept its causes, then seek ways to regularly release and alleviate it. Anything that helps you relax, such as sports, karaoke, shopping, or travel, is fine. Additionally, incorporating relaxing aromatherapy or calming music during sleep can be effective.
Take a Nap
On days when you couldn't get enough sleep at night, take a 15- to 30-minute nap during the day to compensate for sleep deprivation. Sleep debt accumulates, so it's important to resolve it daily.
Also, napping before you feel sleepy can help you maintain a clear head, improving daytime performance. However, be careful not to take long naps, as this can make it difficult to fall asleep at night.
Improve Your Diet
Beverages high in caffeine stimulate the sympathetic nervous system, making it difficult to fall asleep if consumed before bed. Although individual differences exist, it is said that it takes 4 to 6 hours for blood caffeine levels to halve, so those who habitually drink energy drinks, nutritional drinks, coffee, black tea, green tea, oolong tea, or hojicha after evening should be careful.
Alcohol, which is often associated with promoting sleep, also has an awakening effect, so avoid consuming it before bedtime.
Furthermore, to regulate your lifestyle, it is desirable to eat three meals a day at regular times. In particular, breakfast plays a role in resetting your body clock, so try to make it a habit to eat at least a little something.
Bathe Correctly
People feel sleepy when their body temperature drops after having risen, so take a 15-minute bath in lukewarm water around 40°C about 90 minutes before going to bed. However, if you take a bath that is too hot right before bedtime, it can activate the sympathetic nervous system and make you alert, so if you must take a hot bath, keep it short.
Reevaluate Your Sleep Environment
If you struggle with poor sleep quality, experiencing issues like difficulty falling asleep, waking up in the middle of the night, or feeling tired even after sufficient sleep, it's a good idea to re-evaluate your sleep environment.
Review your bedding, such as pillows and mattresses
Pillows and mattresses are very important for sleep quality. Choose products that allow your head and body to sink in comfortably, provide excellent pressure distribution, and make it easy to turn over.
Also, check for breathability and ease of washing before purchasing. If you find changing duvets seasonally cumbersome, washable duvets are a good option.
Be mindful of light before sleep
Exposure to light from computers and smartphones before sleep can disrupt your body clock and make it difficult to fall asleep. If possible, avoid using them one to two hours before bedtime.
Additionally, it's better to use warm-toned lighting, like orange-hued lights, in the bedroom rather than cool-toned white or blue fluorescent lights. Incorporate soft, reddish light or indirect lighting to help you relax.
Control the bedroom temperature appropriately
The ideal comfortable bedroom temperature is said to be around 25–27°C in summer and 15–18°C in winter, with humidity consistently between 50–60%. Sleepiness is encouraged when the body temperature, once elevated, begins to drop, so pay attention to indoor temperature and humidity. If the temperature is too low or too high, your core body temperature may not drop, leading to difficulty falling asleep, increased awakenings during sleep, and a decline in sleep quality.
Also, since external temperatures vary between summer and winter, adjust your sleep environment using bedding, air conditioning, and humidifiers as appropriate for each season.
To Cure Oversleeping, Start by Creating an Ideal Sleep Environment
We've discussed the causes of oversleeping, potential related illnesses, and ways to improve it. By enhancing sleep quality, you can recover from fatigue more efficiently and wake up refreshed at the right time. Therefore, why not focus on "sleep quality" rather than just "sleep duration"?Sleep, said to occupy one-third of our lives, is a crucial time for healing daily fatigue and recovering both mind and body. Therefore, it's essential to reassess your living and sleeping environment. Paying attention to bedding such as pillows and mattresses, which significantly impact sleep quality, is the first step toward achieving the best sleep.
Focus on Sleep Quality! Check Out Brain Sleep Items
Brain Sleep develops a variety of bedding tailored to our customers' sleep needs and concerns. Here, we introduce the features and highlights of our recommended items.
