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18 Causes of Daytime Sleepiness: How to Overcome Tiredness

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Written by Carina Ryder, MS, BSN.
Certified Nurse Midwife, Takoma Park Gynecology
Last updated March 26, 2024

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Why do you feel so tired and sleepy? A comprehensive guide to causes of excessive daytime sleepiness

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Have you ever found yourself wondering about excessive daytime sleepiness?

  • “Why am I always sleepy?”
  • “Why am I falling asleep at work, in the middle of the day?”
  • “Why do I feel tired but can’t sleep?
  • “Why am I waking up tired?”

If so, you are among millions of Americans asking the same questions. If you are having problems sleeping, or are sleeping well but still don’t feel rested, you should consider these 18 reasons you may be sleepy all the time during the day.

Understanding sleep

What happens when you sleep is not completely understood. Studies have shown that it is primarily during sleep that your brain rids itself of toxins such as beta amyloid – a substance implicated in causing Alzheimer’s’ disease.

We also experience several different cycles of sleep at night. We proceed through stages 1 through 3 then one cycles of REM sleep that follows, over and over all night. Slow wave sleep, a crucial stage of sleep for healing, fat burning, muscle building and repair, is the cycle called stage 3 sleep, and it precedes each cycle of REM sleep. If you only sleep a few hours a night, you are not sleeping long enough to repair body and mind, which is why 8 to 9 hours of sleep are ideas. Deep sleep is also crucial for restoring the mind’s ability to learn and process.

Getting adequate sleep is not just a matter of getting rid of your daytime sleepiness, but also a matter of health and well-being. People who do not get adequate sleep have higher rates of inflammation, obesity, diabetes and certain cancers

If you think you do not have time to sleep seven to nine hours of sleep every night, consider this: if you do not get adequate sleep, your executive functioning (the ability to process information and act on it) is compromised – even by just one night’s sleep deprivation, as studies show.

Remember, there is no prize for going the longest time without sleep (which, by the way, is eleven days). It is also very dangerous to work out when you do not sleep, as the heart repairs during sleep as do the rest of the organs.

Low risk reasons for daytime sleepiness

Self-limited and/or unlikely to need intense medical care

1. Sleep deprivation

Sleep deprivation is, simply, not getting enough sleep. This may mean anything from pulling an “all-nighter,” to getting too little sleep on a routine basis.

How much sleep is enough? According to the American Sleep Association, most adults need seven to nine hours of sleep each night. Not getting those seven to nine hours, especially several times a week, is when you will most likely begin to suffering from excessive daytime sleepiness. The obvious answer is to get more sleep.

2. Poor sleep hygiene

Sleep hygiene has nothing to do with brushing your teeth or bathing before bed. Sleep hygiene refers to habits that affect the quality of your sleep. Quality sleep – like adequate sleep - is essential to avoiding daytime sleepiness. When you have habits that interfere with your quality of sleep, you are practicing poor sleep hygiene.

What are some poor sleep hygiene habits?

  • Sleeping on an irregular schedule. Going to bed at the same time every night and getting up at the same time every morning (including weekends!) will improve your quality of sleep and relieve your daytime drowsiness.
  • Consuming coffee or other caffeinated drinks late at night or in the afternoon. Caffeine can stay in your system for 8 hours or more, impacting your ability to sleep and sleep quality.
  • Consuming alcohol, as alcohol use adversely effects your normal sleep cycle.
  • Using sleeping pills. The sleep you get when you take sleeping pills is of a lower quality than what you get when you fall asleep on your own.
  • Using devices that emit blue light, such as computers, cellphones, etcetera, especially within a few hours of going to bed.
  • Taking long naps, especially in the afternoon and evening. A naptime of 30 minutes or less is best if you don’t want to negatively impact your sleep.
  • Working out before bed. Exercising late in the afternoon or right before going to bed makes it difficult to sleep well. Exercise raises the heart rate and causes adrenaline to surge through the system, which can both impact sleep quality. Regular exercise done in the morning or afternoon, however, will help improve your sleep. An overall lack of exercise can cause general fatigue and daytime sleepiness
  • Reading in bed. In fact, doing anything in bed but sleeping might be disruptive to sleep.
  • Eating before bed; you should try to eat at least two hours before going to bed. This also prevents heartburn.

Likely self-limited, but medical care may be helpful or needed

3. Premenstrual syndrome

Women will often begin to suffer from insomnia either during or right before their monthly period. Melatonin, which is a hormone made by the pineal gland and helps regulate sleep, levels decrease during the premenstrual phase of a menstrual cycle, which can cause insomnia. Sleep stages during the menstrual phase are also impacted. The period of deep sleep (slow wave sleep, or SWS) is increased and this can cause fatigue which lasts throughout the day.

4. Idiopathic hypersomnia (sometimes called “long-sleeping disorder”)

Chronic daytime sleepiness can be a symptom of idiopathic (no identifiable cause) hypersomnia (excessive sleepiness).

Idiopathic hypersomnia is characterized by the need to sleep for long periods of time, often - more than ten hours at a time. Despite long periods of sleep, many people with idiopathic hypersomnia are always sleepy, as their sleep is not restorative.

The excessive sleepiness of idiopathic hypersomnia is thought to be caused by a disorder of the nervous system, though true cause of the disorder has yet to be determined. Because the disorder is not fully understood, there is no cure for idiopathic hypersomnia.

Idiopathic hypersomnia should not be confused with African trypanosomiasis (also called “sleeping sickness”), which has a known cause - a parasite found in rural Africa. African trypanosomiasis induces continuous sleep. Even once the disease resolves, there are lingering abnormalities in the sleep-wake cycle. However, there are no known infections in the US.

5. Insomnia disorder

There are different types and classes of insomnia. If you are tired but you cannot sleep, this is called onset insomnia. Or maybe you fall asleep easily but cannot stay asleep, which is referred to as maintenance insomnia. Some fall asleep early but wake up far too early.

Regardless of how you categorize your difficulty sleeping, you have insomnia. Insomnia can leave you feeling drowsy during the day.

If you have insomnia, you are not alone. An estimated 40 million people in the United States experience some form of insomnia every year.

The primary causes of insomnia include:

  • Medical problems, such as chronic pain or reflux
  • Psychiatric problems, such as anxiety and depression
  • Shift work requiring working irregular or non-customary hours
  • Lifestyle habits as described above
  • Sleeping after eating or eating too close to bedtime
  • Smoking, or using alcohol or caffeine
  • Drinking water before bed, such that you wake often to use the bathroom

It is not unusual to experience insomnia during particularly stressful life events, or when traveling across time zones. This acute or episodic type of insomnia should resolve on its own and does not require medical evaluation. If you have sleeping problems at least three nights per week for at least three months, you have chronic insomnia. Insomnia cures may include lifestyle modification or medication. Chronic insomnia deserves medical attention.

Moderate risk causes of daytime sleepiness

Should see a doctor, may need prescription medication or other therapy

6. Fibromyalgia

Fibromyalgia is a condition characterized by generalized pain, malaise and fatigue, sleeping problems, and emotional distress. If you have fibromyalgia, you likely experience problems such as difficulty falling asleep, trouble staying asleep, or waking up too early.

Fibromyalgia causes a disruption in the phases of your sleep cycle. The period of deep sleep (SWS) is decreased in fibromyalgia. This period of deep sleep is believed to be the restorative phase of sleep. Too little time spent in this phase of sleep results in the feeling of not having slept well. Even if you sleep the recommended number of hours, you may not feel refreshed. The drug Xyrem (sodium oxybate) has been found to be effective in treating sleep disorders associated with fibromyalgia. Xyrem increases the period of deep sleep resulting in feeling more restful when awake during the day.

There is currently no cure for fibromyalgia, but there is relief for fibromyalgia pain. Health care providers who treat people with fibromyalgia focus on alleviating the symptoms (pain, fatigue, distress) of fibromyalgia. Rheumatologists are specialists in autoimmune diseases and musculoskeletal disorders. If you have fibromyalgia, a rheumatologist can help you moderate your symptoms.

7. Hypothyroidism

The thyroid is a gland that is located behind your trachea (windpipe). The thyroid produces hormones that regulate your temperature and metabolism. Hypothyroidism may be caused by over treatment of hyperthyroidism (think about it as a battle of hyperthyroidism vs hypothyroidism). Hypothyroidism may also be caused by iodine deficiency, or may be the result of an autoimmune disorder. Hypothyroidism in women is more common than hypothyroidism in men.

In addition to feeling sluggish and sleepy all the time, you may also feel cold even when the people around you feel warm enough. You may start to have difficulty concentrating. Constipation is another symptom of hypothyroidism, as is unintentional weight gain. Once diagnosed, hypothyroidism is easy to treat with medication. There is no specific diet for hypothyroidism. There is no scientific evidence supporting the use of natural remedies for hypothyroidism. Some complementary therapies may help you manage the symptoms of hypothyroidism, but they will not cure it.

8. Mild anemia

Anemia is diagnosed when you have low hemoglobin levels. Hemoglobin is a protein in your red blood cells that contains iron. Hemoglobin carries oxygen from your lungs to all parts of your body. In anemia, your tissues do not get enough oxygen, either because you have a low red blood cell count (too few red blood cells), or because some condition is making your hemoglobin low. Under these circumstances, your heart has to work harder to get adequate oxygen to your tissues.

When your heart has to work extra hard, you become tired more easily, regardless of whether or not you are getting enough quality sleep.

Your hemoglobin may be low either because you had a significant blood loss, you don’t get enough iron in your diet or your body does not absorb iron normally. Iron deficiency anemia is the most common anemia. Things to eat to help alleviate anemia include iron rich food sources. So try eating more animal proteins, such as meat, chicken, fish, eggs, and produce choices like prunes and legumes. prunes. Your health care provider can check to see if you have anemia, and can help you figure out what is causing it.

9. Depression – mild to moderate

Daytime drowsiness can be a symptom of depression. Other symptoms of depression include lack of interest in your usual activities, low energy, difficulty concentrating, feelings of hopelessness, and sleep problems such as insomnia, excessive waking during the night, nightmares, and other sleep disturbances.

The fatigue associated with depression can be both mental and physical. It may or may not be caused by the sleeping difficulties that are common in depression.

Mild to moderate depression, whether it be acute (short term) or chronic (long term) can be treated with medication prescribed by your health care provider. There are things that you can do yourself to help to alleviate depression and daytime sleepiness. Exercising, spending time out-of-doors every day, or talking with a trusted friend or family member may be helpful.

10. Premenstrual dysphoric disorder

Premenstrual dysphoric disorder (PMDD) is an extreme form of premenstrual syndrome. Like PMS, the symptoms of PMDD happen only during the luteal phase (10-14 days before a period) of your menstrual cycle. This may leave you feeling “normal” for half of the month and “out-of-control” for the rest of the month. During the luteal phase, you may also have bloating, exhaustion, irritability and joint pain – all of which seem to magically disappear once your period starts.

If PMDD is causing so much daytime sleepiness that you are unable to function in your day-to-day life, a consultation with a health care provider is warranted. Your health care provider may recommend medications that will reduce the severity of your symptoms, relieve the exhaustion and help you feel more awake during the day.

11. Chronic fatigue syndrome

No one wants to be tired all of the time. If you have chronic fatigue syndrome, your fatigue is persistent and may be interfering with your ability to actively pursue your day-to-day responsibilities and activities. Chronic fatigue syndrome is often (but not always) preceded by a virus, such as Lyme disease, a traumatic physical or psychological experience, . There is inconsistent evidence about the cause of CFS, but we know that full recovery is uncommon.

Some people are affected by both chronic fatigue syndrome and fibromyalgia. Though chronic fatigue syndrome and fibromyalgia have similar symptoms, they are different disorders.

Medical care is important for this condition, but this is unlikely to have severe health consequences

12. Narcolepsy

We have all dosed off while watching a movie or sitting through a boring lecture, but we don’t typically fall asleep in the middle of a conversation, or while eating a meal, or while driving. If you have narcolepsy, you abruptly fall asleep at unpredictable (and often inconvenient) times.

Narcolepsy symptoms may include:

  • Excessive daytime sleepiness
  • Abruptly falling asleep under unusual circumstances
  • Sleep paralysis
  • Dreams so vivid that they feel real
  • Cataplexy (loss of muscle tone)

There is currently no cure for narcolepsy, but there are medications that can help with narcolepsy and the drowsiness it causes. Having good sleep hygiene helps. Relief from narcolepsy can be one of the benefits of physical activity.

13. Periodic limb movement disorder (PLMD)

Though you are probably unaware of it, you may be involuntarily moving your legs (or less often, your arms) during the night as you sleep. The movement may be significant enough to wake you. The interruptions in sleep may or may not wake you, but either way are significant enough to cause havoc in your sleep cycle. People with PLMD often complain of feeling unrested and of daytime sleepiness.

The cause of PLMD is unknown, but may be related to anemia, central nervous system problems or may be genetic. Good sleep hygiene habits will help relief PLMD. If you are not relieved despite having good sleep hygiene, a consultation with your health care provider is necessary.

14. Restless legs syndrome (RLS)

Restless leg syndrome can lead to restless sleep. The leg twitching sensation may be hard to describe. Have you ever had one of those night when you toss and turn because you can’t quiet your mind, if not your body? Imagine that feeling in your legs. Though your legs are still, they have a sensation of ongoing activity until you get up and move around. The achy, “antsy,” an often irresistible urge to move only gets better if you move around.

Restless leg syndrome is different from periodic limb movement disorder. If you have restless leg syndrome, your legs are still, but the sensation you feel in your legs keeps you awake. If you have periodic limb movement disorder, the involuntary movement of your legs may repeatedly wake you from sleep. Restless leg syndrome and periodic limb movement disorder are similar in that they both result in poor sleep, leaving you feeling like you are dragging through your day, and impairing your ability to function at your best.

Restless leg syndrome is quite common throughout pregnancy, and may be aggravated by certain medications, such as allergy medications or SSRIs. SSRIs, or selective serotonin reuptake inhibitors, are used to treat depression and other conditions. Smoking, using alcohol, and consuming caffeine may make your restless leg syndrome worse. If lifestyle changes and adopting good sleep hygiene habits do not help your restless leg syndrome, your health care provider can help. Medication for restless leg treatment is available.

High risk causes of daytime sleepiness

Seeing a doctor is essential to get appropriate treatment/untreated this can be serious

15. Severe anemia

Severe anemia differs from mild anemia in degree, and may require a blood transfusion to correct. When anemia is severe, fatigue may be accompanied by other symptoms such as headache, chest pain, shortness of breath, dizziness, and even loss of consciousness (fainting, or “passing out”). Sometimes, with severe anemia, the heart works so hard that there are disruptions to normal heart rhythms, called arrhythmia, which can be life threatening. Severe anemia is most often the result of a serious accident or injury. If you have chronic blood loss (heavy and prolonged menstrual periods, bleeding inside of your intestines or cancer that causes bleeding), severe anemia may develop.

16. Depression – severe

While some people with severe depression may have unusual bursts of energy, it is more common to have a loss of energy. The loss of energy and feeling of exhaustion continues even if you have adequate sleep. While mild depression is time-limited and can usually be linked to a life event (such as the death of a close friend or loved one), major depression extends beyond one depressive episode – it is chronic. The depression continues even though everything in your life may otherwise be perfect.

If you are having thoughts of hurting yourself or someone else, please get help immediately. The National Suicide Prevention Lifeline provides 24/7 support. The lifeline can also advise you if you are concerned that a friend or family member might be depressed.

17. Obstructive sleep apnea

Sleep is a period of deep relaxation and restoration, both mentally and physically. So, during sleep, all your muscles relax, as do your tongue and some of the soft tissue in your throat. If you have obstructive sleep apnea, your airway becomes blocked as your tongue and other parts of your upper airway become slack and relax.

When your airway becomes blocked, you stop breathing, if only for a couple of seconds. During these seconds, you actually wake up, even though you may not remember waking. Waking up – even briefly like this - interrupts your normal sleep cycle. A normal nighttime sleep cycle is essential to getting adequate rest. When your sleep cycle is interrupted, you miss out on the refreshing benefits of sleep and may wake up feeling like you have not slept at all and, consequently, experience sleepiness throughout the day.

It is important to see your health care provider if you have sleep apnea because apnea increases your risk of developing high blood pressure and heart disease. Fortunately, there is treatment for sleep apnea.

Options for sleep apnea treatment include:

  • CPAP – continuous positive airway pressure. A CPAP machine keeps pressurized air moving into your airway which stops the interruptions in your sleep.
  • Dental devices are used to keep your airway open.
  • Surgery, as a last resort.

18. Post-traumatic brain injury syndrome

Traumatic brain injury can be the result of car accidents, falls, or sport-related injuries. Sleep cycles are often altered after a traumatic brain injury, but as the injury heals, sleep cycles start to normalize again. As the quality of sleep improves, you experience increasing levels of alertness, and daytime sleepiness will begin to occur less and less frequently.

Fortunately, most people with a traumatic brain injury are seen in the emergency room and the injury is recognized and treated. More and more, doctors and ER staff are learning about the widespread problem of unrecognized trauma to the head from sports injuries and concussions, and are being more vigilant in spotting even slight head injuries. If you or your child has been injured in the area of the head, however, always alert any medical professional.

The importance of adequate, quality sleep cannot be over emphasized. Researchers continue to discover more and more benefits of sleep, above and beyond resting enough to feel more awake during the day and to be able to make it through the day without feeling the need for a nap. Although you might be young now and it may seem as if poor sleep is only impacting your days now and then, lack of good sleep will have long-term effects on your mental and physical health and virtually every system of the body.

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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Day nappingPosted November 11, 2023 by A.
I know I have not been sleeping enough through the work weekdays when I nap as much as 3 hours starting after lunch. It can be cultural too from a habit of taking siesta way back home in the Philippines where sleeping for awhile after lunch is ok. There are times though that I still want to take some siesta even if I has enough sleep during the week.
Dr. Peter Steinberg is a board-certified urologist and the director of endourology and kidney stone management at Beth Israel Deaconess Medical Center. He is also an Assistant Professor at Harvard Medical School. He received his undergraduate degree in biochemistry from Middlebury College (1999) and graduated from University of Pennsylvania Medical School (2003). He completed a urology residency a...
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