December 8, 2022

Brain fog is not a medical diagnosis but is the term used by a person to describe sluggishness in thinking or processing information, being fuzzy, or not being mentally sharp. The person is unable to think clearly. Other descriptions are confusion, forgetfulness, lack of focus, and mental fatigue. Brain fog, along with fatigue, body aches, inability to exercise, headache, and difficulty in sleeping, is attributed to the so-called long Covid-19 syndrome.
But what are possible medical causes of brain fog?
In order for the brain to function normally, it has to have an adequate supply of oxygen. Medical conditions that lower the blood flow or oxygen level of the blood cause brain hypoxia, which in turn causes brain fog. Examples are strokes and low blood pressure.
The main food of the brain is glucose, the simplest form of sugar in the body. Low blood sugar (hypoglycemia) or elevated blood sugar (hyperglycemia) disturb brain functioning.
Mental conditions that affect thought processes can also bring about brain fog in the absence of so-called metabolic causes (like oxygen supply, blood flow, and blood sugar levels).
Lack of sleep
Medications – antihistamines (anti-allergy drugs), especially the first generation drugs like diphenhydramine. Pain relievers like tramadol and sedatives.
Travel to a place in a different time zone can also cause mental sluggishness (jet lag).
Chronic fatigue syndrome in which one feels persistent fatigue for longer than six months.
Anemia or low red blood cell count leading to low oxygen-carrying capacity of the blood
Depression, migraines, and Alzheimer’s Disease
Stress, depression, and anxiety disorder
Endocrine disorders like hypothyroidism (reduced activity by the thyroid gland leading to low thyroid hormones)
Poor diet and vitamin B-12 deficiency affects brain function.
In some cases, use of aspartame has been associated with anxiety, mood swings, and brain fog.
Does Covid-19 cause brain fog? It is associated not only with severe or critical disease but also with asymptomatic or mild infection.
How does Covid-19 affect the brain? Direct effects are seen in full-blown encephalitis, stroke, hypoxia or lack of oxygen – medical conditions in which brain dysfunction is obvious or noticeable. But other effects may be more subtle or subclinical, such as the persistent impairment in mental clarity in a person who is ambulatory and who seems to be functioning normally.
In the journal Nature published in May 2021, Drs. Aaron Wong and Akiko Iwasaki discussed the presence of antibodies that are directed against the immune system and the brain. Additional research is being done on the duration of the antibodies and their effects on body tissues.
Brain fog may also be indirectly due to permanent damage to the lungs (scarring or fibrosis), heart (myopathy), kidneys, or other organs. Structural damage to these important organs and the interplay with other symptoms can cause impairment in mental focus.
Can vaccination impair brain functions?
A study by Dr. William Murphy (University of California, U.S.) published in the New England Journal of Medicine in November 2021 discussed the possible role of autoimmune mechanisms triggered by viral proteins. The author, however, said that further studies have to be done on this issue and he continues to encourage vaccination against the virus.
In a normal immune defense, the body produces antibodies that are supposed to be directed against a foreign invader – in Covid-19, the SARS-CoV-2 virus.
In an autoimmune disorder, the body produces antibodies but these attack not only the virus but even normal cells or tissues of a person.
The autoimmune reaction and injury can then cause chronic inflammation that may explain to the commonly described symptoms of long-haulers or long Covid-19 seen in five to 30 percent of affected patients.
Further studies are needed and are being done to further understand causes and to come up with conclusive evidence. In other words, direct links have not been fully established yet. Vaccination is deemed safe and protective and there are new data to show that the protection it confers may last longer than what was shown in earlier studies.


Medical questions and suggestions may be emailed to [email protected] or [email protected]