Brain fog

Cognitive difficulty (chronic in nature and varying from day to day)

What is it?

The word 'brain fog' describes exactly what it feels like: a vague and foggy head and the fog doesn't seem to lift.
Brain fog is not a medical diagnosis. It is an umbrella concept of a cognitive and physical phenomenon that can occur in all kinds of chronic conditions. It can be a result of brain disorders and brain injuries.

Brain fog is the feeling that thinking, understanding and remembering are not going well. One feels unclear, drowsy, forgetful, absent-minded or somewhat confused and one may have difficulty concentrating or solving problems. It may be difficult to come up with words and with what one wants to say. It seems like one is speaking gibberish. One may feel intensely tired and have a blurred vision. It seems like one can't use one's intelligence.


Chronic brain fog or brain fog an occasional day

Some people experience this brain fog phenomenon on a daily basis, while others experience it occasionally. People often experience when they get up that this day will be a foggy day. It may decrease over the course of a day. It can also decrease over time.
Brain fog can also be a chronic inability to organize new information in your brain or recall memories.
It can affect many cognitive functions such as language function, executive functions and sleep.


What precedes a brain fog?

Brain fog cannot always be directly linked to a physical or mental activity. Yet it is known that brain fog can occur when someone has done too many physical or mental activities, for example after a busy agenda or unexpected busyness. Sometimes brain fog is due to poor air quality or sleep problems. When someone sleeps too much or too little, brain fog can follow. Brain fog can also occur as a result of a condition. On this page we list several conditions in which it can occur.


Complaints that may be associated with brain fog

Complaints can be temporary or more chronic in nature.

  • Fatigue
  • Headache
  • Stomach and/or intestinal problems
  • Blurred vision (blurred vision can cause balance problems)
  • Cotton wool head feeling
  • Attention and concentration problems
  • Forgetfulness
  • Difficulty with executive functions such as planning, organizing, maintaining an overview, calculating, but also reduced flexibility



Don't fight against yourself. If you have the occasional brain fog day, try to take that day for granted. The harder you fight, the more difficult a day can be.
Make time for breaks and relaxation. If possible, try to take a walk in the fresh air. Do yourself a favor.
Reduce caffeine consumption in the afternoon and evening.
Try to practice good sleep hygiene.
Try to get enough sleep before a busier day.
Eat healthy food; with lots of proteins and vitamins.
Check the air quality. If you live in an area with a lot of air pollution, consider purchasing an air purifier.


Read the page dealing with fatigue (neurofatigue) and the page dealing with overstimulation.

Use digital reminders, lists or other planning tools. Stick to planning and lists and other routines.

Ask yourself whether you are overloaded by the responsibility at your (volunteer) work, or as a (co-)parent and whether you are constantly multitasking. Focusing on just one task can sometimes reduce the brain fog.

If you have a brain fog day every day, it may be advisable to request cognitive therapy or have an occupational therapist look at your resilience and your resilience and mental and physical strain.

Explain to friends and family how they can help.


Brain fog occurs with

Brain fog is an umbrella concept. It occurs with:

  • brain damage, brain injury
  • disturbed brain function
  • reduced cerebral blood flow (for example in case of severe anemia)
  • dehydration
  • a hormonal disruption
  • infectious disease
  • autoimmune disease
  • medicinal cause (for example consider chemotherapy)
  • social and emotional factors
  • stressors


It can occur with the following conditions, among others:
Brain injury and brain disorders. Sleep disorders including Central Sleep Apnea Syndrome (CSAS) and Obstructive Sleep Apnea Syndrome (OSAS), which cause the brain to receive too little oxygen during sleep. COVID-19 and LONG-COVID.
It occurs with disruption of the dopamine system, depression, PTSD, migraine, anemia, diabetes, autoimmune diseases such as Graves' disease and Hashimoto's disease; both are thyroid disorders and in multiple sclerosis and Sjögren's syndrome. In systemic lupus (systemic lupus erythematosus or SLE); which is also a chronic autoimmune disease. Brain fog occurs in infectious diseases, fibromyalgia, chronic fatigue syndrome, after chemotherapy treatment (chemo brain) in addition to debilitating fatigue, in dehydration, due to hormone changes in women going through menopause and also due to disturbed sleep in these women. It can be a result of Alzheimer's disease and many other conditions.

This list is not complete.


It can also be a result of our fast, hectic, stressful society with great pressure to perform and too little sleep.

In case diseases are suspected

If diseases are suspected, a doctor will have to rule out the following: fluctuating glucose levels, poor liver, kidney and thyroid function, nutritional deficiencies, infections and inflammatory diseases, sleep disorder, brain disorders and autoimmune disease.