Sleep and Multiple Sclerosis: The Crucial Impact on Cognition

The fundamental link between sleep and cognition

Sleep is not a passive state where the brain simply shuts down. On the contrary, it is a period of intense brain activity during which essential processes occur. While we sleep, our brain works actively: it consolidates the day's memories, transfers information from short-term memory to long-term memory, and eliminates the metabolic waste accumulated during wakefulness. Quality sleep is therefore absolutely essential for proper cognitive functioning.

The different phases of sleep each play a specific role in brain functions. Deep slow-wave sleep is particularly important for the consolidation of declarative memory (facts and events) and the brain's physical recovery. REM sleep, the dreaming phase, is crucial for procedural memory (skills), creativity, and emotional regulation. Disrupting these phases, as is often the case in MS, has direct consequences on the next day's cognitive abilities.

Recent research has highlighted the role of the glymphatic system, a network of channels in the brain that activates mainly during deep sleep to remove toxic proteins and cellular waste. This cleaning process is essential to prevent the accumulation of harmful substances that may contribute to cognitive decline. For people with MS, where the brain is already under pressure, this nocturnal cleaning is particularly valuable.

Common sleep disorders in MS

Sleep disorders are remarkably common in people with multiple sclerosis, much more so than in the general population. This high prevalence is explained by multiple factors directly or indirectly related to the disease: brain lesions can affect sleep regulation centers, some MS symptoms disrupt nights, and treatments can have side effects on sleep.

Insomnia: the most common disorder

Insomnia, defined as difficulty falling asleep, maintaining sleep, or early waking, affects nearly half of people with MS. It can be linked to anxiety about the disease, neuropathic pain that intensifies at night, muscle spasms, or simply daily worries amplified by chronic fatigue. Insomnia creates a particularly detrimental vicious circle: lack of sleep worsens fatigue and cognitive disorders, increasing stress and making falling asleep even more difficult.

• Onset insomnia: Difficulty falling asleep despite feeling tired, often linked to stress and rumination
• Maintenance insomnia: Frequent awakenings during the night with difficulty falling back asleep
• Early waking: Waking up several hours before the desired time without being able to fall back asleep

Restless leg syndrome

Restless leg syndrome (RLS) is significantly more common in people with MS than in the general population. It manifests as unpleasant sensations in the legs (tingling, pulling, burning) accompanied by an irresistible need to move them, occurring mainly at rest and in the evening. These symptoms make falling asleep extremely difficult and cause frequent nocturnal awakenings that fragment sleep.

Sleep apnea

Sleep apnea, characterized by repeated breathing pauses during sleep, is also more common in MS. It causes unconscious micro-awakenings that fragment sleep and prevent reaching restorative deep phases. Affected individuals wake up tired despite an apparently sufficient sleep duration and often suffer from excessive daytime sleepiness that further aggravates cognitive fatigue.

Consequences of sleep disorders on the brain

The consequences of disturbed sleep on cognitive functions are major and well-documented scientifically. For people with MS whose brain must already compensate for the disease lesions, these effects are even more pronounced and can significantly impact daily quality of life and professional abilities.

Impact on memory

Memory is the cognitive function most directly affected by lack of sleep. Without quality sleep, the process of memory consolidation cannot occur properly. Learned information from the previous day is not securely stored and is more easily forgotten. Working memory, which allows holding information temporarily to manipulate it mentally, is particularly sensitive to lack of sleep.

Impact on attention and concentration

After a bad night, the ability to maintain attention on a task decreases drastically. Distractions become harder to ignore, the mind wanders more easily, and sustained concentration becomes a real challenge. For people with MS who already have attention difficulties linked to the disease, this effect of lack of sleep can be particularly disabling.

• Sustained attention: Reduced ability to stay focused on a long and monotonous task
• Selective attention: Increased difficulty filtering distractions and focusing on the essential
• Divided attention: Multitasking becomes even more difficult and exhausting than usual

Impact on processing speed and executive functions

Lack of sleep significantly slows down information processing speed. The tired brain takes longer to perceive, analyze, and respond to stimuli. Executive functions, which enable planning, organizing, making decisions, and adapting to new situations, are also impaired. Mental flexibility decreases, decisions are less thought out, and problem-solving becomes more laborious.

I long underestimated the impact of my nights on my MS. I thought my fatigue and concentration difficulties were solely due to the disease. When I finally treated my sleep apnea, I discovered a different person. I feel more alive, more alert, capable of things I thought I had lost forever.

Valerie, 49 years old, MS for 15 years

Identify and assess your sleep disorders

The first step to improving your sleep is to precisely identify the nature of your disorders. Not all sleep problems are alike and do not require the same solutions. A thorough evaluation, possibly with the help of professionals, allows targeting the most appropriate interventions for your particular situation.

Self-observation: keeping a sleep diary

Keeping a sleep diary for two to three weeks is a valuable tool for better understanding your sleep patterns. Note each day the time of going to bed and getting up, the estimated time to fall asleep, nocturnal awakenings and their duration, subjective sleep quality, and your energy level upon waking. This information will be useful for yourself but also for any professional you consult.

Signs that should alert

• Loud and irregular snoring: May indicate sleep apnea requiring evaluation
• Sensation of choking or suffocation at night: Classic sign of sleep apnea
• Uncontrollable leg movements: Suggest restless leg syndrome
• Excessive daytime sleepiness: Despite apparently sufficient sleep duration
• Waking up with headaches: May indicate sleep breathing disorders
• Fatigue not relieved by sleep: Sleep does not seem restorative

Basic sleep hygiene

Sleep hygiene refers to the set of habits and behaviors that promote quality sleep. These measures, simple in appearance, can have a considerable impact on the quality of sleep. For people with MS, adhering to these principles is particularly important as the brain needs all the chances to regenerate effectively.

Regularity of schedules

The human body functions according to circadian rhythms, an internal biological clock that regulates many functions including sleep. This clock adjusts based on regular signals, particularly the time of going to bed and getting up. Maintaining regular sleep schedules, even on weekends, helps synchronize this clock and facilitates both falling asleep and waking up. Significant schedule variations disrupt rhythms and can create a real social jet-lag detrimental to sleep.

Optimal sleep environment

Habits to adopt and avoid

• Limit screens in the evening: Blue light from screens inhibits melatonin. Stop screens 1 to 2 hours before bedtime
• Avoid caffeine after 2 pm: Caffeine has a half-life of 5 to 7 hours and can disrupt sleep even when consumed in the afternoon
• Avoid alcohol in the evening: Alcohol facilitates sleep onset but fragments sleep and reduces its quality
• Exercise regularly: But not too late in the evening, intense physical activity can delay sleep onset
• Avoid heavy meals in the evening: Difficult digestion can disrupt sleep
• Reserve the bed for sleep: Do not work, eat, or watch television in bed

Advanced strategies for better sleep

Beyond basic sleep hygiene, more specific strategies can help people with MS improve their nights. These approaches target particular issues related to the disease and can make a significant difference when basic measures are not enough.

Managing nocturia

MS bladder disorders, particularly nocturia (need to urinate at night), often fragment sleep. Some strategies can help: limit evening drinks without dehydrating, completely empty the bladder before bed, and talk to your neurologist who can propose specific treatments for bladder disorders.

Managing nocturnal pain

Neuropathic pain and muscle spasms can intensify at night and disrupt sleep. Relaxation techniques before bed, gentle stretches, applying heat or cold depending on what relieves, and discussing pain treatment options with your doctor can improve the situation.

Relaxation and stress management

• Jacobson's progressive relaxation: Muscle contraction-relaxation technique that reduces physical tension
• Abdominal breathing: Slow, deep breathing that activates the parasympathetic nervous system
• Mindfulness meditation: Helps calm rumination and detach from worries
• Guided visualization: Imagining soothing scenes to facilitate relaxation
• Sophrology: Combines relaxation, breathing, and positive visualization

Sleep and cognitive stimulation: a positive synergy

Sleep and cognitive stimulation maintain a positive bidirectional relationship. On one hand, good sleep optimizes the benefits of cognitive training by allowing better consolidation of learning. On the other, regular cognitive stimulation with programs like EDITH and JOE can help improve sleep quality by structuring the day and promoting healthy fatigue.

Optimizing the timing of cognitive training

The time of day when you do your cognitive exercises can influence both their effectiveness and your sleep. For most people, morning is an optimal time because cognitive energy is highest after a night of rest. Avoid stimulating exercises just before bedtime as they can activate the brain and delay sleep onset. However, gentle exercises with EDITH in the early evening can be part of a pre-sleep relaxation routine.

Sleep consolidates progress

The learning achieved during cognitive training with EDITH or JOE is consolidated during sleep. It is during the night that the brain transfers new skills from short-term memory to long-term memory. Good sleep after a training session maximizes the benefits of that session. Conversely, poor sleep can limit consolidation and reduce training effectiveness.

Getting support for sleep disorders

Sleep disorders in MS can be complex and multifactorial. Do not hesitate to seek help from professionals to evaluate and treat them. Appropriate care can transform your quality of life and cognitive abilities.

Professionals to consult

• Your neurologist: First point of contact to discuss your sleep disorders in the context of your MS
• Sleep doctor: Specialist who can perform thorough examinations and propose specific treatments
• CBT psychologist: Cognitive-behavioral therapy for insomnia is the reference treatment for chronic insomnia
• Urologist: If bladder disorders significantly disrupt your sleep
• Pulmonologist: In case of suspected sleep apnea