What exactly is brain fog and where does it come from?
Brain fog most likely has multiple simultaneous causes, of which a leaking blood-brain barrier in long COVID is the best substantiated. Exactly what goes wrong in the brain differs depending on the underlying condition, so the approach also varies by situation.
Brain fog is not an official diagnosis but a term for a cluster of cognitive complaints: difficulty concentrating, a faltering short-term memory, a sense of confusion and slowed information processing. It affects people with long COVID, ME/CFS (myalgic encephalomyelitis/chronic fatigue syndrome), coeliac disease and burnout, as well as people dealing with persistent stress or mental fatigue.
In long COVID, brain fog has been studied most extensively. A protective barrier between the blood and the brain, known as the blood-brain barrier, is demonstrably leaky in a proportion of patients. This allows inflammatory substances from the blood to reach the brain. In this research, blood cells adhered more strongly to cerebral blood vessels, and exposing those blood vessels to the blood of long COVID patients in turn triggered greater local inflammation. This points to ongoing inflammatory damage as a core mechanism. Additionally, persistent viral remnants and a dysregulated immune system are suspected, but these remain preliminary findings.
ME/CFS presents a similar picture, although the impairments in attention and information processing are on average more severe than in long COVID. The fact that the symptom patterns overlap so strongly suggests that part of the underlying mechanism is shared, but this has not yet been proven.
Gut-related brain fog also exists: in most people with coeliac disease, cognitive complaints arise after gluten intake. After twelve months of a gluten-free diet, the complaints improved measurably, although the precise mechanism is unclear. Indirect inflammatory activity is likely involved, rather than gluten itself.
Mental fatigue and prolonged stress contribute to cognitive complaints such as concentration problems and slowed reaction speed. Whether stress causes brain fog or is in fact amplified by it has not yet been clearly disentangled. What is clear is that untreated mental fatigue can develop into a more persistent pattern of complaints.
This answer is based on several review studies and a systematic review, supplemented by two specific mechanistic studies. The strongest evidence concerns the damaged blood-brain barrier in long COVID, which has been demonstrated using imaging and laboratory tests. The mechanisms behind it, such as viral persistence and autoimmunity, are less well established: the researchers themselves describe these as preliminary. For coeliac disease and stress, the associations have been observed but cause and effect have not been unambiguously demonstrated.
Does creatine supplementation reduce brain fog?
Creatine may ease cognitive complaints, but the effect depends heavily on your situation: people with chronic fatigue, sleep deprivation or a plant-based diet are most likely to benefit, while for healthy, well-rested individuals it appears to do little.
How does creatine get into the brain?
Creatine reaches the brain via a single specific transport protein in the blood-brain barrier. In people with a normally functioning transport system, oral supplementation may modestly top up brain stores, though this happens much more slowly and to a far lesser extent than in muscles.
What are the causes of memory loss?
Memory loss has many possible causes that differ greatly from one another. If you suddenly develop memory problems, always have them assessed by a doctor so that a treatable cause is not missed.
What does one bad night of sleep do to your brain?
One bad night demonstrably affects your attention, reaction speed and mood, and the consequences are larger than most people expect. Caffeine helps temporarily, but sleep remains the only real solution.
What does a vitamin D deficiency do to your brain?
A vitamin D deficiency is associated with a higher risk of cognitive decline and dementia, but whether correcting it with supplements actually protects your brain has not yet been proven. If you think you may be deficient, discuss it with your doctor.
What does air pollution do to your brain in the long run?
Long-term exposure to fine particulate matter is associated with a higher risk of dementia and cognitive decline, even at younger ages. The evidence is not yet watertight, but strong enough to take air quality seriously when making choices about where to live and how to get around.