Subjective brain fog: a four-dimensional characterization in 25,796 participants, 2024, Alim-Marvasti et al

[forestglip]

Subjective brain fog: a four-dimensional characterization in 25,796 participants
Ali Alim-Marvasti, Matteo Ciocca, Narayan Kuleindiren, Aaron Lin, Hamzah Selim, Mohammad Mahmud

Abstract
Importance: Brain fog is associated with significant morbidity and reduced productivity and gained increasing attention after COVID-19. However, this subjective state has not been systematically characterised.

Objective: To characterise self-reported brain fog.

Design: We systematically studied the cross-sectional associations between 29 a priori variables with the presence of "brain fog." The variables were grouped into four categories: demographics, symptoms and functional impairments, comorbidities and potential risk factors (including lifestyle factors), and cognitive score. Univariate methods determined the correlates of brain fog, with long-COVID and non-long-COVID subgroups. XGBoost machine learning model retrospectively characterised subjective brain fog. Bonferroni-corrected statistical significance was set at 5%.

Setting: Digital application for remote data collection.

Participants: 25,796 individuals over the age of 18 who downloaded and completed the application.

Results: 7,280 of 25,796 individuals (28.2%) reported experiencing brain fog, who were generally older (mean brain fog 35.7 ± 11.9 years vs. 32.8 ± 11.6 years, p < 0.0001) and more likely to be female (OR = 1.2, p < 0.001). Associated symptoms and functional impairments included difficulty focusing or concentrating (OR = 3.3), feeling irritable (OR = 1.6), difficulty relaxing (OR = 1.2, all p < 0.0001), difficulty following conversations (OR = 2.2), remembering appointments (OR = 1.9), completing paperwork and performing mental arithmetic (ORs = 1.8, all p < 0.0001). Comorbidities included long-COVID-19 (OR = 3.8, p < 0.0001), concussions (OR = 2.4, p < 0.0001), and higher migraine disability assessment scores (MIDAS) (+34.1%, all p < 0.0001). Cognitive scores were marginally lower with brain fog (-0.1 std., p < 0.001). XGBoost achieved a training accuracy of 85% with cross-validated accuracy of 74%, and the features most predictive of brain fog in the model were difficulty focusing and following conversations, long-COVID, and severity of migraines.

Conclusions and relevance: This is the largest study characterising subjective brain fog as an impairment of concentration associated with functional impairments in activities of daily living. Brain fog was particularly associated with a history of long-COVID-19, migraines, concussion, and with 0.1 standard deviations lower cognitive scores, especially on modified Stroop testing, suggesting impairments in the ability to inhibit cognitive interference. Further prospective studies in unselected brain fog sufferers should explore the full spectrum of brain fog symptoms to differentiate it from its associated conditions.

Conflict of interest statement
All authors are or have been employees of Mindset Technologies, Ltd., London, UK.

Link | Full Text (Frontiers in Human Neuroscience, open access)

 

[Creekside]

Is it just me, or does this seem to be a circular definition: that their results (from questionnaires) matches their definition of brainfog, which is defined by the results? Seems pretty useless.

 

[wigglethemouse]

I was reading up on vestibular migraines and read that many people with migraines also suffer from quite significant brain fog. This paper seems to support that.

Brain fog was particularly associated with a history of long-COVID-19, migraines, concussion

The American Migraine Foundation has this to say about the possible cause of brain fog in Migraines

While more research is needed in this area, it’s believed that brain fog is linked to the cortical depression in the brain leading up to a migraine attack. Cortical depression is something that happens to the cells in your brain (cortex). It’s an electrical and blood flow process that often spreads from the back of the brain (where vision is controlled) to the front of the brain (where thinking is controlled). As the cortical depression moves over your brain, it can slow your thinking or make it hard to find words.

Given the repeated finding of reduced cerebral blood flow in ME/CFS, could brain fog in ME/CFS be as simple as being caused by reduced blood flow much like that described with migraines? I'd be interested in others thoughts on this along the lines of recent threads looking for disease clues (some by @Jonathan Edwards).

I've also been wondering if the reduced blood flow is affecting the vestibular system causing a subset of those with ME/CFS to suffer light-headedness, dizziness, light sensitivities, and motion sensitivities. Much like with vestibular migraine (note vestibular migraine does not always come with headache).

 

[Turtle]

Maybe reduced cerebral blood flow and more immature red blood cells (Canadian research). Higher turnover of RBC was also found in astronauts.
Viscosity of the blood can be higher. RBC deformability can be decreased. (A K Saha 2018/19)
Could all that affect blood oxygen levels? Less blood to the brain and even less oxygen in the blood (OI)?

 

[Mij]

A preliminary clinical study related to vestibular migraine and cognitive dysfunction, 2024

BACKGROUND AND PURPOSE: Vestibular migraine (VM) is a common clinical disorder with a genetic predisposition characterised by recurrent episodes of dizziness/vertigo. Patients often complain of the presence of cognitive dysfunction manifestations such as memory loss, which causes great distress in daily life.

In this study, we will explore the characteristics and possible risk factors of VM-related cognitive dysfunction by observing the cognitive function and vestibular function status of VM patients, laying the foundation for further exploration of the mechanisms of VM-related cognitive dysfunction.

METHODS: This study included 61 patients with VM and 30 healthy individuals matched for age, gender, and education level. All subjects underwent the Addenbrooke's Cognitive Examination-Revised (ACE-R), Dizziness Handicap Inventory (DHI), Hospital Anxiety and Depression Scale (HADS), Patient Health Questionnaire-9 (PHQ-9), and Generalized Anxiety Disorder-7 (GAD-7) at the first time of enrollment. Based on the ACE-R scores, the VM group was divided into the VM with cognitive dysfunction (VM-CogD) group (ACE-R < 86) and the VM without cognitive dysfunction (VM-NoCogD) group (ACE-R ≥ 86).

The VM-CogD group was further categorized based on DHI scores into mild, moderate, and severe dizziness/vertigo subgroups (DHI ≤30 for mild, 30 < DHI ≤ 60 as moderate, and DHI > 60 as severe). All subjects underwent the head-shaking test, head-impluse test, test of skew, Romberg test, Unterberger test, videonystagmography, and caloric test to evaluate their vestibular function including the semicircular canals, vestibulo-ocular reflex pathway, and vestibulo-spinal reflex pathway.

Differential analysis, correlation analysis, and ROC curve analysis were used to analyze the characteristics and influencing factors of the above clinical indicators in VM patients. It was considered that p-value < 0.05 was statistically significant, and |r| > 0.3 indicated a good correlation. and varying degrees of cognitive dysfunction, and cognitive function is affected by age, duration of illness, years of education, and vestibular function; 2. VM is a functional disorder, and the function disturbance, in conjunction with anxiety and depression, may participate in the occurrence of development of cognitive dysfunction in VM.

LINK