Tired All the Time: Is It Sleepiness, or Is It Fatigue?

Multiple sclerosis (MS) may be a “snowflake” disease with many differences from person to person, but one symptom that plagues virtually every person with MS is the feeling of being tired all the time.1

It may seem fruitless to distinguish between the nuances of tiredness. But 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:1

  • 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 2 key measures of tiredness that can be confused.


Sleepiness (also referred to as drowsiness or hypersomnia) is generally a temporary condition that can be traced to sleep that is of poor quality or fragmented.2

Sleep deprivation can lead to excessive daytime sleepiness, which is something that needs to be examined by a doctor. Many sleep disorders cause excessive daytime sleepiness (EDS). EDS is 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.1,2

Sleep disorders that are common causes of EDS include:2,3

  • Narcolepsy
  • Idiopathic hypersomnia (IH)
  • Obstructive sleep apnea (OSA)
  • Central sleep apnea (CSA)
  • Restless legs syndrome (RLS)

Extreme “night owls” or “early birds” have major shifts in their circadian 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 can be at odds with their work schedules and lead to sleep deprivation.2

Jet lag is also a kind of circadian rhythm disorder, as is the sleep deprivation linked to 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.2,3

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. These symptoms may include muscle spasticity at night, neurological misfiring in damaged areas of the brain that facilitate sleep-wake functions, or sleep-disrupting pain.1

Plus, medicines that we might be taking for our MS symptoms (or for treatment of the disease itself) may have EDS as an adverse side effect.1

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 future reduce the severity of other MS symptoms like pain or mood swings.1-3


Fatigue tends to be related to medical conditions or to the overuse of one’s brain or body. Fatigue refers to a state of physical or mental exhaustion, or a combination of both.1,4

Often, a person with physical fatigue who cannot overcome their day-to-day tiredness will go on to develop mental or emotional fatigue as a result:1,4

  • 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 quicksand, or their limbs are made of lead.
  • Mental fatigue: These problems of tiredness are more commonly referred to as cognitive dysfunction (among people with MS, the term "cognitive 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.

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 diseases and disorders that cause fatigue, which makes it important to pay attention to your symptoms.1,4

Why should we know the difference between sleepiness and fatigue?

As you already know from first-hand experience as a person with MS, being clear with your specialists regarding the nature of your symptoms is key 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.1,4

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 are 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, and 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 2022 study found a high percentage of fatigue, EDS, and depression in people with MS. The study's researchers noted that it can be hard to tell the difference between fatigue from sleepiness and depression and that proper testing is needed to help doctors tell the difference in patients.5

That being said, it is important for doctors to screen their MS patients for sleep disorders 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 inflammation, cognitive problems, hypersensitivity to pain, and mood dysfunction.2

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.

Do yourself a favor and look into your symptoms rather than chalking them up to aging or assuming it’s just MS at work. There’s no reason you need to suffer more just because you have MS! And finally, make sleep a priority.

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