Fatigue in MS is common, but it is often not investigated or managed properly. This post highlights the complexity of MS-related fatigue and explains why and how to manage it holistically. 

Key points

• The different mechanisms underlying MS-related fatigue are explained.
• The MS disease process, the burden of living with MS, and other factors such as drug side effects, comorbidities and lifestyle choices may all contribute to fatigue in MS.
• Practical guidance is provided on managing many aspects of MS-related fatigue, using a holistic and systematic approach.
• Not all fatigue is MS-related; it is important to ascertain if your fatigue could be due to another disease process.

Fatigue is one of the most disabling of all the symptoms of MS. It is the symptom that over 50% of people with MS would most like to be rid of. MS-related fatigue has several underlying mechanisms.

Fatigue caused by MS disease processes

Inflammation in the brain

Inflammatory mediators or cytokines associated with MS – in particular, interleukin-1 (IL-1) and TNF-alpha – trigger ‘sickness behaviour’. This is the response to inflammation that forces us to rest and sleep so that our body can recover. Sickness behaviour is also the body’s response to a viral infection such as flu; in fact, many people with MS describe their fatigue as being like the fatigue they experience with flu. 

Sickness behaviour from an evolutionary perspective is well conserved and occurs in most animals. This type of fatigue needs to be managed by switching off ongoing inflammation in the brain. Many people with MS who take a highly effective DMT report feeling much better and free from fatigue and/or brain fog. This is why recent-onset fatigue that cannot be explained by other factors (see below) may indicate MS disease activity. At present, fatigue on its own does not constitute a relapse.

Many patients with MS who have had COVID-19 tell me that MS-related cog-fog and fatigue feel like the cog-fog and fatigue of COVID-19 and long-COVID. As many as one in four people with long-COVID experience cog-fog, which includes problems in attention, language fluency, processing speed, executive function, and memory: these are the same problems that affect people with MS. 

Cog-fog related to MS and to COVID-19 could be linked to the same inflammatory mechanisms. This syndrome of systemic inflammation causing profound fatigue and cog-fog is not new. Some people with MS who have a systemic infection take weeks or months to return to normal; some patients with more advanced MS never return to their original baseline. This is why, as part of the holistic management of MS, we need to treat and prevent systemic infections as best we can.

The overlap between COVID-19 and MS-related cog-fog raises the question whether both are due to viral infections. There is some evidence of recent Epstein-Barr virus (EBV) reactivation in patients with long-COVID,¹ suggesting that the EBV rather than the SARS-CoV-2 may be causing long-COVID symptoms. This is important because chronic EBV infection has been associated with chronic fatigue syndrome. It has also been suggested that chemo-brain is due to similar mechanisms, i.e. chemotherapy triggers CNS inflammation, which causes cog-fog.

Neural plasticity

When parts of the brain are damaged by MS, other areas are co-opted to help take over, or supplement, the function of the damaged area. In other words, people with MS use more brain power than people without MS to complete the same task. This usually manifests as mental fatigue and is why people with MS have difficulty concentrating for prolonged periods and multitasking. At present we have no specific treatment for this type of fatigue, but some patients find amantadine or modafinil helpful. There is also some emerging evidence that fampridine may help with cognitive fatigue. However, preventing damage in the first place should prevent this type of fatigue.

Exercise-related conduction block

Damage to axons that conduct electrical impulses is the reason why people with MS notice their legs getting weaker or another neurological symptom getting worse with exercise. We think this is due to demyelinated or remyelinated axons failing to conduct electrical impulses when they become exhausted. Exercise-induced fatigue is probably the same as temperature-related fatigue; a rise in body temperature also causes vulnerable axons to block and stop conducting. To deal with this type of fatigue we need therapies to promote remyelination and to increase conduction. These types of fatigue are treated by rest, cooling and possibly drugs such as fampridine that improve conduction. At the heart of this type of fatigue is localised energy failure.

Fatigue from living with MS symptoms

Temperature sensitivity

Many people with MS are temperature sensitive. Typically, high temperatures worsen fatigue, but low temperatures also affect some patients. Many people with MS manipulate their behaviour to avoid hot or cold environments. Some find it helpful to use cooling suits, but these are costly and are not covered by NHS funding. Cold or ice baths, swimming and air conditioning can all help with temperature-related fatigue.

Case example

One of my patients had a walk-in butcher’s fridge installed in her house, and she spends 30 minutes there 4 ̶ 5 times a day to manage her fatigue. She is a wheelchair user, and she sits in her wheelchair in the fridge.

Menstrual and menopausal fatigue

Menstrual (or catamenial) fatigue is a form of temperature-related fatigue that occurs in women during the second half of the menstrual cycle when their body temperature increases. It responds to paracetamol and to non-steroidal anti-inflammatory drugs such as ibuprofen and naproxen. Fatigue is a common symptom of menopause too; some women with MS who are menopausal and have fatigue find hormone replacement therapy helpful. 

Whether or not men go through a ‘menopause’ is a moot point. Testosterone levels do drop with age, however, and some male patients find that testosterone replacement therapy helps their MS-related fatigue. In the UK, the indications for testosterone replacement therapy are very well defined and do not include MS-related fatigue, so most people with MS who want to try this therapy need to pay for a private prescription.

Bladder problems

Intermittent waking due to bladder problems may result in fatigue from disrupted sleep. Bladder problems may also contribute to insomnia, with the affected individual needing to visit the bathroom frequently and unable to relax into sleep. For detailed guidance on managing bladder problems, particularly at night, please see the bladder and bowel section of the website, particularly the article on nocturia.  

Insomnia due to pain and discomfort

Other disease-related factors that contribute to fatigue include insomnia from pain, discomfort of being unable to turn in bed and restless legs syndrome (RLS). RLS is common in people with MS, affects sleep quality and is associated with poor cognition. For detailed guidance on managing these MS symptoms, please see the post entitled Sleep disrupted by pain and discomfort.  

A case scenario

“A 28-year-old woman with early relapsing ̶ remitting MS, on glatiramer acetate, and little overt neurological impairment suffers from severe fatigue, which is worse during the latter half of her menstrual cycle. She has recently split up with her long-term partner because of the impact her symptoms have had on her relationship. She has also had to stop working as a bank clerk because of her fatigue.” Prof G’s response This patient needs to be examined and will need an MRI and a lumbar puncture to measure her spinal fluid neurofilament levels. If she has evident inflammatory disease activity, her DMT will need to be switched. She needs a full medical assessment, which includes a screen for comorbidities. The patient complains of cognitive fatigue and, despite not having much physical disability, she was found to have a high brain MS lesion load and noticeable brain volume loss. A formal neuropsychological assessment to establish if she has cognitive impairment would allow her to be referred to a cognitive rehabilitation programme; this can target specific areas to help her cope with her cognitive deficits. To combat fatigue during her menstrual cycle, this patient did well on naproxen, which is longer acting than ibuprofen and paracetamol. Naproxen only needs to be taken during the second half of her cycle. She was screened for poor sleep hygiene, and she volunteered intermittent early morning waking due to bladder problems and anxiety. Both would need to be addressed as part of her fatigue management programme. It was clear that the patient had both depression and anxiety, which were related to the impact of MS on her occupational and social functioning. This must be managed with cognitive behavioural therapy (CBT), mindfulness and an exercise programme. If this approach is not helpful, then I would suggest the judicious use of an antidepressant and, failing this, a referral to a psychiatrist and/or psychologist.

Fatigue resulting from other factors

Comorbidities and other diseases

Comorbidities and other diseases related to MS can cause fatigue and should be screened for. These include infections (see above). In people with more advanced MS, the urinary tract is most often affected, but other sites of infection include the sinuses, teeth, lungs, skin (intertrigo and pressure sores) and bowels.

Fatigue is common with thyroid disease; an underactive thyroid gland (hypothyroidism) and an overactive gland (hyperthyroidism, or thyrotoxicosis) cause fatigue. Diabetes, other endocrine (hormonal) problems, anaemia and heart, kidney, liver or lung diseases all cause fatigue.

Side effects of drugs

Fatigue is a common side effect of many medications, particularly drugs that cause sedation and some DMTs. Flu-like side effects from interferon-beta, for example, may make fatigue worse. Anticholinergics and antispasticity drugs are sedating, blunt cognition and may worsen MS-related fatigue. If you have fatigue, therefore, it is important to review your medications. MS is associated with polypharmacy, but some of the medications that cause or exacerbate fatigue can be reduced in dose, stopped or potentially replaced with alternatives that don’t exacerbate fatigue.

Lack of sleep and/or sleep disorders

Poor sleep means you feel tired in the morning. Most people with MS have poor sleep hygiene and almost half have an actual sleep disorder. A clue to this is how you feel in the morning and whether you have excessive daytime sleepiness. If you wake up in the morning and don’t feel refreshed and/or you fall asleep frequently during the day, you need a formal sleep assessment. You can complete the Epworth Sleepiness Scale online to see if you have a problem.

Depression and anxiety

Fatigue is a common symptom of depression and anxiety. Of the many online screening tools for depression and anxiety, the best one to use if you have MS is probably the Hospital Anxiety and Depression Scale (HADS). 

Obesity

Being overweight requires additional energy to perform physical tasks, and obesity itself causes fatigue. Recently an association has been found between obesity and depression. Obesity also predisposes you to sleep disorders; obese people with MS are more likely to have obstructive sleep apnoea. For all these reasons you should engage with lifestyle and wellness programmes to manage obesity and fatigue. 

Deconditioning

Deconditioning is simply the term we use for being unfit. If you are unfit, performing a demanding physical task makes you tired. Deconditioning is treated with exercise, which paradoxically can reduce fatigue. Patients may claim that exercising makes their fatigue worse. Yes, that does happen, but if you persevere and get fitter your fatigue often improves. The important thing is to start a graded exercise programme and build up slowly. Exercise does some incredible things to the brain, many of which explain why it is effective at treating not only fatigue but also depression and anxiety. Exercise is a form of ‘disease-modifying therapy’ and hence everyone with MS should be participating in an exercise programme. 

Poor nutrition and ‘food coma’

Some people with MS are anorexic and eat very poorly; as a result, they have little energy. Although this is quite rare, I have had a few such patients over the years. Similarly, overnutrition may have the same effect. Some of the hormones your gut produces cause you to feel tired and want to sleep; this is the so-called siesta effect (also referred to as food coma or postprandial hypersomnolence). Reducing the size of your meals and changing your eating behaviour may improve this. Postprandial hypersomnolence has two components.

1. A state of perceived low energy related to activation of the parasympathetic nervous system (which is part of the autonomic nervous system) in response to expansion of the stomach and duodenum from a meal. In general, the parasympathetic nervous system slows everything down. 
2. A specific state of sleepiness triggered by the hormone cholecystokinin that helps digest food and regulate appetite. It is released in response to eating and to changes in the firing and activation of specific brain regions. The coupling, or interaction, of digestion and the brain is referred to as ‘neurohormonal modulation of sleep’ and it underlies the reflexes responsible for postprandial hypersomnolence. There is therefore a well-studied biological reason why we feel sleepy after eating a meal. 

Managing food coma – practical tips

The first patient who alerted me to the problem of food coma in MS was so affected by postprandial hypersomnolence that she now eats only one meal a day, late in the evening. She can then ‘crash’ and go to sleep about an hour after eating. She needs to be functional during the day but cannot do her professional work if she eats anything substantial during working hours because of her overwhelming desire to sleep. She has tried caffeine, modafinil and amantadine to counteract postprandial hypersomnolence, but all these substances had only a small effect. Other patients reporting postprandial hypersomnolence derive some benefit from the judicious use of stimulants. You can start by self-medicating with caffeine, but this may have the drawback of worsening your bladder function. Please note, however, that it is not advisable to take stimulants later than about 3 pm or 4 pm because they have a long half-life and can cause insomnia. Some patients find carbohydrate-rich foods particularly potent at inducing ‘food coma’. Indeed, glucose-induced insulin secretion is one of the drivers of this behavioural response. This may be why people who fast or eat very low-carbohydrate or ketogenic diets describe heightened alertness and an ability to concentrate for long periods. Another option is to reduce your meal size: instead of large meals, try eating multiple small snacks during the day. Exercise has helped some patients deal with postprandial hypersomnolence. I am not sure exactly how exercise works – possibly by lowering glucose and insulin levels and improving insulin sensitivity. The latter will reduce hyperinsulinaemia, which not only causes postprandial hypersomnolence but is an important driver and component of metabolic syndrome and obesity. Postprandial hypersomnolence will be worse if you already suffer from a sleep disorder and excessive daytime sleepiness. Most people with MS have a sleep disorder, so there is little point in focusing on postprandial hypersomnolence and ignoring the elephant in the room.

Using your energy effectively

One strategy to manage MS-related fatigue is to imagine your energy levels as a battery, i.e. you have only so much energy in the day. People with MS have smaller batteries than people without MS and therefore need to plan their day and activities to maximise their use of energy. For example, if you do something tiring in the morning, you should rest in the afternoon to conserve energy for evening activities. Similarly, if you find some activities very tiring, such as taking a hot shower or bath, plan to do this in the evening before bed.

Conclusion

It is apparent from this discussion that fatigue in MS is more complex than we realise. So be careful, or at least wary, if your neurologist simply wants to reach for the prescription pad to get you out of the consultation room. Any MS-related symptoms that can affect sleep need to be managed accordingly. Like other MS-related problems, a holistic and systematic approach is needed to manage and treat MS-related fatigue correctly. Not all fatigue is MS-related. This is why it is important to take a step backwards and ask yourself if your fatigue could be due to another disease process.

Reference

1. Gold JE et al. Investigation of long COVID prevalence and its relationship to Epstein-Barr virus reactivation. Pathogens 2021;10:763.