Tired all the time: Is it sleepiness or is it fatigue?

Last updated: June 2018

Multiple sclerosis may be a “snowflake” disease with myriad variations unique to each person who has it, but one symptom that plagues virtually every person with MS is the feeling of being tired all the time.

It may seem fruitless to distinguish between the nuances of tiredness, and yet, from a medical perspective, differentiating sleepiness from fatigue is key to getting proper treatment for your symptoms.

The spectrum of tiredness

During the day, we may experience different kinds of tiredness.

  • For some, it’s a weighty feeling in the limbs that makes physical movement difficult.
  • Sometimes we yawn all day long and crave naps.
  • We may feel “cognitive fog,” in which thoughts and words come slowly.
  • We may become overwhelmed with a sense of exhaustion that we feel in our brains, our bones, and our moods.

Does it matter that we distinguish between these kinds of tiredness?

Tired is tired… or is there a meaningful difference?

The difference between sleepiness and fatigue

Sleepiness and fatigue are two key measures of tiredness that can be confused.


Sleepiness (also referred to as drowsiness or somnolence) is generally a temporary condition that can be traced to sleep that is of poor quality or fragmented.

Sleep deprivation can lead to excessive daytime sleepiness, which is something that needs to be examined by a physician. Many sleep disorders cause EDS (Excessive daytime sleepiness, defined as an unrelenting desire to sleep in the middle of the day), and it’s quite possible that a person with MS can also have at least one or more of these conditions, as quite a few sleep disorders are fairly common.

Sleep disorders that figure prominently in causing EDS include:

  • Narcolepsy: An uncommon form of hypersomnia with distinct symptoms (cataplexy, sleep paralysis, and/or sleep hallucinations) that is thought to be an autoimmune disorder related to severe neurochemical imbalances in the brain meant to regulate wakefulness.
  • Idiopathic hypersomnia (IH): This is often diagnosed when someone with symptoms of narcolepsy has been tested for it and it has been ruled out. Idiopathic means “unknown;” IH refers to extreme sleepiness unexplained by any other cause.
  • Obstructive sleep apnea (OSA): One of the most common sleep disorders, OSA refers to a breathing disorder caused by mechanical issues of the upper airway during sleep. It leads to frequent, lengthy pauses in breathing which reduce blood oxygen levels to dangerously levels.
  • Central sleep apnea (CSA): Like OSA, this breathing disorder leads to hypoxemia (a condition of low blood oxygen). However, CSA is caused by misfiring messages in the brain which fail to prompt the diaphragm to breathe during periods of sleep, leading to long pauses in breathing.
  • Restless legs syndrome (RLS): Another extremely common sleep disorder, RLS involves problematic sensations in the legs (and sometimes the arms) at bedtime which disrupt one’s transition from wake to sleep. RLS often requires showers, movement, or massage to relieve. RLS has been found to be very common among MSers and is also linked with higher disability.

Another related condition is periodic leg movement disorder (PLMD), in which the legs twitch or jerk while one sleeps, usually in a distinctive pattern, causing sleep fragmentation that the sufferer may not even be aware of.

  • Circadian rhythm disorders: These relate to dysfunction with the circadian system, which is influenced by light-dark cycles, one’s sleep drive (the biological need to sleep at the end of a long period of wakefulness), and other lifestyle behaviors.

People with seasonal affective disorder experience circadian imbalances due to longer periods of darkness during the fall and winter that misinform the body clock, leading to daytime sleepiness.

Extreme “night owls” or “early birds” has major shifts in their rhythms that cause them to go to bed much later or rise much earlier than others around them. In either case, their sleep-wake schedules came be at odds with their work schedules and can lead to sleep deprivation.

Jet lag is also a kind of circadian rhythm disorder, as is the sleep deprivation associated with working the graveyard shift (shift work disorder). Any time we consciously choose to stay awake when we should be asleep, or sleep when we should be awake, can lead to sleep debt.

For the person with MS, it can be hard to know if sleepiness is caused by sleep deprivation from an underlying sleep disorder or by their own MS-related symptoms, such as muscle spasticity at night, neurological misfiring in damaged areas of the brain that facilitate sleep-wake functions, or sleep-disrupting pain.

In addition, medications that we might be taking for our MS symptoms (or for treatment of the disease itself) may have EDS as an adverse side effect.

In any case, it’s worthwhile to have these concerns checked out by a sleep specialist; nearly all sleep disorders are treatable and, once treated, can often lead to an additional reduction in the severity of other MS symptoms (such as pain or mood swings).


Fatigue tends to be related to medical conditions or to the overuse of one’s brain or body. Also referred to as tiredness, exhausted, listlessness, lethargy, or malaise, it refers to a state of physical or mental exhaustion, or a combination of both.

Often, a person with physical fatigue, who cannot overcome their day-to-day malaise, will go on to develop mental or emotional fatigue as a result.

  • Physical fatigue: This refers to one’s inability to physically function at normal capacity. It could mean struggling to hold a coffee cup or walk across the room, or it could mean being completely incapable of getting out of bed in the morning, despite having full use of one’s arms and legs.People with physical fatigue describe it as feeling like they’ve just run a marathon, they are walking through deep water or quick sand, or their limbs are made of lead.
  • Mental fatigue: These problems of tiredness are more commonly referred to as cognitive dysfunction (among MSers, the term “cognitive fog” or “cog fog” is a popular description).Mental fatigue occurs when problems arise with concentration, focus, comprehension, or alertness, and executive functions like decision-making or judgment become impaired. Speech and memory may also be affected.
  • Emotional fatigue: Sometimes a combination of physical and mental fatigue can lead to an additional problem with regulating one’s moods. It makes sense; feeling unable to perform the ordinary tasks of daily life can lead to frustration, anger, depression, anxiety, and other swings in mood.Enough disruptions in one’s life caused fatigue can build up and lead to emotional outbursts that may have neurochemical as well as environmental foundations.

It seems counterintuitive to say so, but those who suffer the symptoms of insomnia—and who do not have any other underlying, untreated sleep disorder—are at least as likely to experience all three kinds of fatigue as well, and they may also experience EDS.

Fatigue is related to many medical conditions as well as to their treatments. While MS can be a clear cause of fatigue, it may not be the only one. A person with MS may also have other disease and disorders that cause fatigue, which makes it important to pay attention to one’s symptoms.

For instance, someone with MS who struggles to breathe easily as they walk may also have asthma or an infection in the lungs, even cancer that’s not detected.

Why should we know the difference between sleepiness and fatigue?

Improved communication

As you already know from first-hand experience as an MSer, being clear with your specialists regarding the nature of your symptoms is crucial for accurately identifying and treating your symptoms.

For instance, if you are experiencing emotional fatigue, the doctor will ask you several questions to help identify what it’s caused by. Mood swings can be part of the MS journey, but they might also be part of a separate mental health disorder or the result of taking a certain kind of medication, for instance.

Or, they could simply be the result of being “sick and tired of being sick and tired.”

Sometimes it’s not MS…

Using myself as an example, I have degenerative joint disease in my left big toe and both of my wrists. The pain, numbness, and sense of muscular fatigue I experience in these is not caused by MS.

I discovered these issues during the process of getting diagnosed; my neurologist sent me to several specialists to investigate them as part of that “ruling out” process that an MS diagnosis requires.

Because I identified these problems, I now treat them separately. But without a proper diagnosis, I would most certainly be more disabled by these symptoms: in fact, part of the pain, grip weakness, numbness in my wrists was also caused by carpal tunnel syndrome! After having surgical procedures for both hands, I have greater functionality now than I’ve had in decades.

…but sometimes, it is

A study conducted by Pennsylvania State University uncovered evidence that problems with depression and sleep deficits were more likely to predict fatigue issues in people with MS and not the actual diagnostic severity of their condition, with sleep disturbance being the most likely contributor to fatigue in MS patients.

The National Sleep Foundation recommends that physicians screen for sleep problems among their MS patients and know the best options for treating them. Having clarity about the root cause of your symptoms makes it easier for you and your doctor to deal with them most effectively.

The secondary benefits of treating sleepiness or fatigue

Treating other health conditions that can cause EDS or fatigue can deliver the wonderful secondary benefit of improving your overall health and symptom load.

For instance, people who treat their OSA find that they have more energy, are more clear-headed, experience less pain, and find it easier to maintain a stable mood; this is because OSA also causes systemic inflammation (which leads to physical fatigue), cognitive problems, hypersensitivity to pain, and mood dysfunction.

If you have EDS or fatigue and are newly diagnosed with MS—or you’ve had MS for a while but are experiencing new or different symptoms—it’s important to investigate them to determine if they’re actually related to your condition or if they may require separate diagnosis and treatment.

Note: If you are middle aged or older, the aging process alone may lead to the development of other conditions. Arthritis, for instance, can lead to both depression and fatigue, and sleep apnea is a common cause among older people with EDS.

Do yourself a favor and look into your symptoms, rather than chalk it up to aging or assume it’s just the “monster” at work. There’s no reason you need to suffer more just because you have MS!

And finally, make sleep a priority. The National Sleep Foundation says:

“Getting a good night's sleep helps to alleviate many common symptoms of MS, including chronic fatigue, mood and memory problems.”

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This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The MultipleSclerosis.net team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

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