Medical Glossary

← Home

Medical Glossary

123 terms explained in plain language.

acetylcholine: The primary neurotransmitter for memory, learning, and attention. Anticholinergic medications (Benadryl, some antidepressants) block it — a common hidden cause of brain fog.
adenosine: A chemical that builds up during waking hours, creating sleep pressure. Caffeine works by blocking adenosine receptors — which is why it masks fatigue rather than fixing it.
AHI: Apnea-Hypopnea Index — the number of breathing pauses (apneas) plus partial obstructions (hypopneas) per hour of sleep. AHI >5 = mild OSA, >15 = moderate, >30 = severe. The primary measure used to diagnose and track sleep apnea severity.
alpha rhythm: Brain waves in the 8-13 Hz frequency range, associated with relaxed alertness, attention readiness, and cortical arousal regulation. Reduced posterior alpha is consistently found in brain fog patients across Long COVID, ME/CFS, and fibromyalgia studies (Babiloni 2024). Think of alpha as your brain's 'ready' signal — when it's low, you're not cognitively primed.
amyloid: A protein that can accumulate in the brain when the glymphatic system isn't clearing waste effectively. Associated with Alzheimer's disease. Deep sleep is essential for amyloid clearance.
anticholinergic: Medications that block acetylcholine — the neurotransmitter for memory and learning. Common culprits: Benadryl, older antidepressants, bladder medications. A leading hidden cause of drug-induced brain fog.
apnea: Sleep apnea — repeated pauses in breathing during sleep that drop oxygen levels and fragment sleep architecture. Causes morning brain fog, daytime fatigue, and long-term cognitive decline if untreated.
autophagy: The cell's self-cleaning process — damaged components are broken down and recycled. Triggered by fasting, exercise, and sleep. Impaired autophagy leads to cellular debris accumulation and cognitive decline.
BBB: Blood-brain barrier — the selective membrane protecting the brain from harmful substances in the bloodstream. Damage to the BBB is a key driver of brain fog.
BDNF: Brain-derived neurotrophic factor — a protein that promotes neuron growth, survival, and new connections. Exercise is the most reliable way to boost it. Low BDNF is linked to depression, cognitive decline, and slow recovery from brain fog.
benzodiazepine: A class of sedative medications (Valium, Xanax, Ativan) that enhance GABA activity. Effective short-term for anxiety but cause cognitive impairment, memory problems, and dependence with regular use.
biomarker: A measurable substance in the body that indicates a biological state or condition. Blood biomarkers like ferritin, hs-CRP, and TSH help identify the root cause of brain fog objectively.
biopsychosocial model: A framework viewing health as the product of biological, psychological, and social factors interacting — not just physical disease. A 793-person ML study validated this for Long COVID: stress (PSS) and social support (MSPSS) ranked among the top 15 predictors alongside clinical measures.
blood pooling: In POTS and dysautonomia, blood accumulates in the lower body when standing due to poor venous return. Causes reduced cerebral perfusion and brain fog. Visible as purple/red discoloration in feet (acrocyanosis). Treated with compression garments and counter-maneuvers.
blood-brain barrier: A selective membrane that controls what enters the brain from the bloodstream. When damaged by inflammation, toxins, or gut permeability, harmful substances leak in and trigger neuroinflammation.
butyrate: A short-chain fatty acid produced when gut bacteria ferment dietary fibre. Strengthens the gut lining, reduces inflammation, and crosses the blood-brain barrier to directly support neurons.
CBC: Complete blood count — a basic blood panel that measures red cells, white cells, and platelets. Can reveal anaemia, infection, or immune activation contributing to brain fog.
cerebral hypoperfusion: Reduced blood flow to the brain. In POTS, this occurs on standing when blood pools in the legs instead of reaching the brain. Directly causes brain fog, difficulty concentrating, and cognitive slowing. Measured via transcranial Doppler ultrasound.
chronicity: The tendency of a condition to persist over time. In Long COVID, 85.7% of patients still met diagnostic criteria at 1 year, confirming the condition's chronic nature requiring active management.
circadian: Relating to the body's ~24-hour internal clock. Circadian disruption (irregular sleep times, night-shift work, blue light at night) impairs melatonin production, cortisol rhythm, and cognitive performance.
cortisol: The primary stress hormone. Short bursts are useful (focus, alertness). Chronic elevation from ongoing stress damages the hippocampus, impairs sleep, and drives brain fog. Measured via morning saliva or blood test.
counter-maneuvers: Physical movements to increase blood return to the heart in POTS and orthostatic intolerance. Examples: leg crossing with thigh tensing, squatting, toe raises, fist clenching. Used before and during standing to prevent symptoms.
CPAP: Continuous Positive Airway Pressure — the gold-standard treatment for obstructive sleep apnea. A bedside machine delivers pressurized air through a mask to keep the airway open during sleep. Cognitive improvement often occurs within days to weeks.
cytokine: Chemical messengers released by immune cells. Pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) drive brain fog by disrupting neuron communication. Anti-inflammatory cytokines help resolve it.
DAO: Diamine oxidase — the enzyme that breaks down histamine in the gut. Low DAO activity leads to histamine intolerance: brain fog, headaches, and flushing after aged cheese, wine, or fermented foods.
deconditioning: A state of reduced physical fitness from prolonged inactivity. In POTS, deconditioning worsens symptoms by reducing blood volume and cardiac output. The Levine/CHOP recumbent exercise protocol specifically addresses this without triggering symptom flares.
dendritic: Relating to dendrites — the branch-like extensions of neurons that receive signals from other neurons. Dendritic sprouting (growth of new branches) is a sign of healthy neuroplasticity.
DII: Dietary Inflammatory Index — a literature-derived scoring system that rates the inflammatory potential of a diet based on 30+ nutrients. Higher DII = more pro-inflammatory. UK Biobank research proves DII predicts anxiety, depression, sleep disorders, and dementia risk through measurable blood markers.
dopamine: A neurotransmitter governing motivation, reward, and focus. Low dopamine = difficulty starting tasks, poor concentration, and lack of drive. Iron (ferritin) is essential for dopamine synthesis.
drift diffusion model: A computational model describing how the brain accumulates information when making decisions. In Long COVID, reduced drift rate and altered decision boundaries show slowed information processing and need for more evidence before deciding.
dysautonomia: Dysfunction of the autonomic nervous system — the automatic controller of heart rate, blood pressure, digestion, and temperature. POTS is the most common form. Causes dizziness, fatigue, and brain fog on standing. Often co-occurs with EDS and MCAS.
dysbiosis: An imbalance in gut bacteria — too many inflammatory species, too few protective ones. Drives systemic inflammation, impairs nutrient absorption, and disrupts neurotransmitter production.
elimination diet: A structured approach to identifying food triggers: remove suspected foods for 2–4 weeks, then reintroduce one at a time while monitoring symptoms. The gold standard for finding diet-driven brain fog.
Epworth: Epworth Sleepiness Scale — an 8-question self-assessment measuring daytime sleepiness. Score your likelihood of dozing in different situations (reading, watching TV, as a passenger). Score ≥10 = excessive daytime sleepiness, suggesting a sleep disorder.
feature importance: In machine learning, a score indicating how much a variable contributes to predicting an outcome. In the Staggs (2025) Long COVID study, functional status (PCFS) had the highest importance (0.0766), followed by fatigue (0.0720) and sleep quality (0.0666).
ferritin: The protein that stores iron in your body. Optimal for brain function: 50–100 ng/mL. Below 30 impairs dopamine synthesis even when technically 'in range.' Many labs set the lower limit at 12 — far too low for cognitive health.
folate: Vitamin B9 — essential for methylation, DNA repair, and neurotransmitter production. Low folate impairs memory and mood. Found in leafy greens, legumes, and fortified foods. The methylated form (5-MTHF) is better absorbed.
Free T3: The active form of thyroid hormone that directly affects brain metabolism. Low Free T3 with normal TSH is a common missed cause of brain fog — your brain is running on a low-power setting.
Free T4: The storage form of thyroid hormone. Your body converts T4 → T3. Poor conversion (common with selenium or iron deficiency) means normal T4 but low active T3 — and brain fog.
GABA: Gamma-aminobutyric acid — the brain's main calming neurotransmitter. Balances excitatory signals. Benzodiazepines and alcohol artificially boost GABA, which is why withdrawal causes rebound anxiety and fog.
glutamate: The brain's primary excitatory neurotransmitter. Essential for learning, but excess glutamate is neurotoxic. MSG sensitivity and neuroinflammation can cause glutamate overload.
glymphatic: The brain's waste-clearance system, most active during deep sleep. It flushes out metabolic debris (including amyloid proteins linked to Alzheimer's). Poor sleep = poor glymphatic drainage = brain fog.
Hashimoto: Hashimoto's thyroiditis — an autoimmune condition where the immune system attacks the thyroid gland. The most common cause of hypothyroidism. Detected by elevated TPO antibodies, often years before TSH goes abnormal.
HbA1c: Glycated haemoglobin — measures average blood sugar over 2–3 months. Above 5.7% suggests prediabetes. Blood sugar instability is a major driver of brain fog, even at 'normal' levels.
HBOT: Hyperbaric oxygen therapy — breathing pure oxygen in a pressurised chamber. Promotes neuroplasticity and reduces neuroinflammation. The strongest evidence is for post-COVID brain fog (60-session protocols at 2.0 ATA).
histamine: A compound involved in immune response, digestion, and brain function. Excess histamine (from high-histamine foods or low DAO enzyme) causes brain fog, headaches, skin flushing, and nasal congestion.
HPA axis: Hypothalamic-pituitary-adrenal axis — the brain-to-adrenal gland communication system that controls your stress response. Chronic activation leads to cortisol dysregulation, fatigue, and cognitive impairment.
hs-CRP: High-sensitivity C-reactive protein — a blood marker for systemic inflammation. Optimal: below 1.0 mg/L. Elevated levels indicate your immune system is active, which can drive brain fog. Cheap, widely available test.
hyperadrenergic POTS: A subtype of POTS with elevated norepinephrine, causing anxiety, tremor, and high blood pressure on standing in addition to tachycardia. May respond to clonidine, guanfacine, or beta-blockers. Diagnosed by standing norepinephrine levels >600 pg/mL.
hypothyroid: Underactive thyroid — insufficient thyroid hormone production. Causes fatigue, brain fog, weight gain, and cold intolerance. Subclinical hypothyroidism (normal TSH, low Free T3) is frequently missed.
IL-1: Interleukin-1β — a pro-inflammatory cytokine that reduces neurogenesis and disrupts sleep architecture. One of the key drivers of sickness behaviour and brain fog.
IL-6: Interleukin-6 — a pro-inflammatory cytokine. Elevated in Long COVID, chronic stress, and autoimmune conditions. Directly impairs hippocampal function (memory) and prefrontal cortex (focus).
intestinal permeability: Often called 'leaky gut' — when the gut lining develops gaps, allowing bacteria, toxins, and undigested food particles to enter the bloodstream and trigger immune activation.
k-means clustering: A machine learning algorithm that groups similar data points together. Applied to Long COVID symptoms, it identified 6 distinct phenotypes: sleep-dominant (58% PASC), triple-mix (80%), mental-dominant (66%), asymptomatic (1%), physical-dominant (51%), and physical+mental (85%).
ketogenic: A very-low-carbohydrate, high-fat diet that shifts the brain's fuel source from glucose to ketones. Some evidence for reducing neuroinflammation and improving mitochondrial function.
LDN: Low-dose naltrexone — naltrexone at 1–4.5 mg (vs. standard 50 mg) modulates the immune system and reduces neuroinflammation. Used off-label for Long COVID, fibromyalgia, and autoimmune brain fog. Requires prescription.
leaky gut: The colloquial term for increased intestinal permeability — gaps in the gut lining that allow inflammatory molecules into the bloodstream, triggering immune activation and brain fog.
Levine Protocol: Also called the CHOP protocol. A structured recumbent exercise program proven effective for POTS (86% adolescent remission rate). Starts with horizontal exercises (rowing, swimming, recumbent bike) and progressively adds upright training over 3-6 months.
lipopolysaccharide: Bacterial fragments (endotoxins) from gram-negative gut bacteria. When they leak through a damaged gut barrier into the bloodstream, they trigger a powerful inflammatory response that reaches the brain.
LPS: Lipopolysaccharides — bacterial endotoxins that trigger inflammation when they leak from the gut into the bloodstream through a damaged intestinal barrier.
mandibular advancement device: An oral appliance custom-fitted by a sleep dentist to treat sleep apnea. Advances the lower jaw forward to open the airway during sleep. Alternative to CPAP for mild-moderate OSA or patients who can't tolerate CPAP.
mast cell: Immune cells that release histamine and other chemicals during allergic and inflammatory reactions. Overactive mast cells (MCAS) can cause widespread symptoms including brain fog.
MCAS: Mast cell activation syndrome — mast cells release excessive histamine and other mediators, causing brain fog, flushing, hives, GI symptoms, and reactions to foods/chemicals. Often overlaps with POTS and EDS.
melatonin: The hormone that signals your body to sleep. Produced ~16 hours after morning light exposure. Blue light at night suppresses it. Supplementing is less effective than fixing the light cycle.
methylmalonic: Methylmalonic acid (MMA) — a more sensitive marker for B12 deficiency than serum B12 alone. Elevated MMA indicates functional B12 deficiency even when serum B12 is borderline normal.
microbiome: The community of trillions of bacteria, fungi, and viruses in your gut. An imbalanced microbiome (dysbiosis) drives inflammation via the gut-brain axis, directly affecting mood and cognition.
microglia: The brain's resident immune cells. When activated by infection, stress, or injury, they release inflammatory chemicals that can impair cognition. Think of them as the brain's security guards — helpful in short bursts, destructive when they won't stand down.
mitochondri: Mitochondria — the energy-producing structures inside every cell. When they malfunction (from inflammation, nutrient deficiency, or viral damage), cells can't produce enough ATP (energy). Result: fatigue and brain fog.
MSPSS: Multidimensional Scale of Perceived Social Support — a 12-item questionnaire measuring support from family, friends, and significant others. Ranked 13th predictor in Long COVID ML classification. Low social support = measurably worse outcomes. Treatable via social prescribing and support groups.
NAC: N-acetyl cysteine — an amino acid supplement that replenishes glutathione (the body's master antioxidant), reduces neuroinflammation, and helps break down mucus. Dose: 600–1,200 mg/day.
NAD: Nicotinamide adenine dinucleotide — a coenzyme essential for cellular energy production. Declines with age. NAD+ precursors (NR, NMN) are being studied for cognitive recovery, especially in Long COVID.
NASA Lean Test: A simple orthostatic screening test: stand leaning against a wall (heels 6 inches from wall) for 10 minutes. Monitor heart rate and symptoms. HR increase ≥30 bpm or symptom onset suggests POTS/orthostatic intolerance. More practical than formal tilt table for initial screening.
neurogenesis: The creation of new neurons, primarily in the hippocampus (memory centre). Exercise, sleep, and omega-3s promote it. Chronic inflammation suppresses it.
neuroinflammation: Inflammation specifically in the brain and nervous system. Unlike a swollen ankle, you can't see or feel it directly — but it disrupts processing speed, memory, and executive function. Measured indirectly via hs-CRP and other blood markers.
Neuropathic POTS: A subtype of POTS caused by damage to small fiber nerves controlling blood vessels. Often associated with autoimmune conditions. May respond to IVIG or other immunomodulatory treatments. Diagnosed via skin biopsy showing reduced nerve fiber density.
neuroplasticity: The brain's ability to rewire itself by forming new neural connections. Brain fog doesn't cause permanent damage — neuroplasticity means recovery is possible once the underlying cause is addressed.
NF-kB: Nuclear factor kappa-B — a protein complex that controls inflammation gene expression. When chronically activated, it drives sustained neuroinflammation. Curcumin, omega-3s, and NAC help modulate it.
NLR: Neutrophil-to-Lymphocyte Ratio — a calculated inflammation marker from a standard CBC. NLR >2.0 suggests systemic inflammation. UK Biobank DII research shows NLR mediates the diet→brain disorder pathway. Calculate: Neutrophils ÷ Lymphocytes.
NMN: Nicotinamide mononucleotide — a precursor to NAD+, the coenzyme essential for mitochondrial energy production. Emerging evidence for cognitive benefits, particularly in age-related and post-viral brain fog.
noradrenaline: Also called norepinephrine. The neurotransmitter that governs alertness. In hyperadrenergic POTS, excessive noradrenaline causes anxiety, tremor, and palpitations alongside orthostatic symptoms.
norepinephrine: A neurotransmitter and stress hormone that governs alertness and attention. Too little = foggy and fatigued. Too much = anxious and scattered. Cold exposure triggers a reliable spike.
Nrf2: A protein that activates your body's antioxidant defence genes. Sulforaphane (from broccoli sprouts), curcumin, and exercise activate Nrf2. It's one of the most powerful natural anti-inflammatory pathways.
orthostatic intolerance: Symptoms triggered by upright posture: dizziness, brain fog, palpitations, nausea, weakness. Umbrella term that includes POTS, orthostatic hypotension, and other conditions where the body cannot properly regulate blood flow when vertical.
P300: An event-related potential (brain response) occurring approximately 300 milliseconds after a stimulus, reflecting cognitive processing speed and attention allocation. Significantly delayed in brain fog patients (Fabio 2024: F(1,39)=16.11, p<0.01), meaning the brain takes measurably longer to classify relevant information. Persists at 8 months post-infection.
parasympathetic: The 'rest-and-digest' branch of the autonomic nervous system, controlled primarily by the vagus nerve. Activating it reduces heart rate, lowers inflammation, and supports cognitive recovery.
PASC: Post-Acute Sequelae of SARS-CoV-2 infection — the formal medical term for Long COVID. Defined as symptoms persisting or emerging >4 weeks after acute COVID-19 infection. A 793-person ML study achieved 77.2% accuracy classifying PASC.
PCFS: Post-COVID Functional Scale — a validated measure of functional status after COVID-19, grading ability to perform daily activities. Ranked #1 predictor (importance 0.0766) in ML classification — how much you can do is the strongest signal of Long COVID severity.
PEA: Palmitoylethanolamide — a naturally occurring fatty acid with anti-inflammatory and neuroprotective properties. Works by calming overactive microglia. Dose: 600–1,200 mg/day. Well-tolerated with few interactions.
PEM: Post-exertional malaise — the hallmark symptom of ME/CFS and many Long COVID cases. Symptoms worsen 12-72 hours after physical, cognitive, or emotional exertion. Presence of PEM changes treatment strategy: graded exercise is contraindicated; pacing is essential.
photobiomodulation: Using specific wavelengths of red or near-infrared light to stimulate mitochondrial function in brain cells. Transcranial devices (worn on the head) have shown cognitive improvements in Long COVID trials.
PLR: Platelet-to-Lymphocyte Ratio — a blood inflammation marker calculated from CBC. Elevated PLR indicates vascular inflammation and increased stroke risk. Part of the DII-mediated pathway to brain disorders.
polysomno: Polysomnography — an overnight sleep study that monitors brain waves, breathing, oxygen levels, and muscle activity. The gold standard for diagnosing sleep apnea, UARS, and other sleep disorders.
polysomnography: An overnight in-lab sleep study that monitors brain waves, breathing, oxygen levels, heart rhythm, and body position. The gold standard for diagnosing sleep apnea and UARS. Unlike home tests, it can detect subtle respiratory effort-related arousals (RERAs).
POTS: Postural orthostatic tachycardia syndrome — heart rate rises excessively (≥30 bpm) when standing. Causes dizziness, fatigue, and brain fog on standing. Screen: lie down 5 min, take pulse, stand, retake at 2/5/10 min.
prefrontal cortex: The front region of your brain responsible for planning, decision-making, working memory, and focus. It's the first area to go offline under inflammation or stress — which is why brain fog hits complex tasks before simple ones.
PROMIS cognitive: Patient-Reported Outcomes Measurement Information System Cognitive Function — a validated questionnaire measuring subjective cognitive complaints. Ranked 5th predictor (importance 0.0626) in Long COVID ML classification. Gives doctors a validated number instead of 'I feel foggy.'
PSS-10: Perceived Stress Scale — a 10-item validated questionnaire measuring stress levels. Ranked 11th predictor (importance 0.0421) in Long COVID ML classification. Score 14-26 = moderate stress, 27+ = high. High stress is as predictive as clinical measures like headache.
quantitative EEG: Digital analysis of brain electrical activity patterns, breaking the raw EEG signal into frequency bands (delta, theta, alpha, beta, gamma) to quantify brain function. Research shows measurable differences in brain fog patients vs healthy controls: reduced alpha (8-13 Hz) and increased theta (4-7 Hz). Currently research-grade only — not yet a standard clinical diagnostic for brain fog.
random forest: A machine learning algorithm that builds multiple decision trees and combines their predictions. Used in the Staggs (2025) Long COVID study to identify feature importance and achieve 77.2% classification accuracy.
RERA: Respiratory Effort-Related Arousal — a partial airway obstruction that doesn't meet criteria for apnea or hypopnea but still disrupts sleep. The hallmark of UARS. Not scored on most home sleep tests — requires in-lab polysomnography to detect.
RERAs: Respiratory effort-related arousals — brief awakenings caused by increased breathing effort that don't meet the criteria for apnea. Cause fragmented sleep and daytime fog. Many sleep labs don't score them unless asked.
SCFA: Short-chain fatty acids — metabolites produced by gut bacteria from dietary fibre (butyrate, propionate, acetate). They strengthen the gut barrier, reduce inflammation, and support brain function.
serotonin: A neurotransmitter regulating mood, sleep, and gut function. ~95% is produced in the gut, which is why gut health directly affects mood and cognition. Precursor: tryptophan (from protein).
short-chain fatty acid: Metabolites (butyrate, propionate, acetate) produced when gut bacteria ferment fibre. They strengthen the gut lining, reduce systemic inflammation, and directly support neuron health.
SIBO: Small intestinal bacterial overgrowth — bacteria that should live in the large intestine colonise the small intestine, causing bloating, malabsorption, and brain fog via the gut-brain axis. Diagnosed by breath test.
SII: Systemic Immune-Inflammation Index — a composite blood marker calculated from CBC that tracks overall immune activation. Part of the DII inflammation cascade linking diet to brain disorders in UK Biobank research.
social prescribing: A healthcare approach where clinicians prescribe social activities (support groups, community programs, peer connections) alongside medical treatments. Validated by ML evidence that social support (MSPSS) ranks among top 15 Long COVID predictors.
statin: Cholesterol-lowering medications. Some people report cognitive side effects (memory problems, confusion). Lipophilic statins (atorvastatin, simvastatin) cross the blood-brain barrier more readily than hydrophilic ones.
STOP-BANG: An 8-question sleep apnea screening tool: Snoring, Tiredness, Observed apneas, Pressure (high BP), BMI >35, Age >50, Neck circumference >40cm, Gender (male). Score ≥3 = significant OSA risk. Takes 1 minute. Free. Do it now.
sympathetic: The 'fight-or-flight' branch of the autonomic nervous system. Chronic sympathetic dominance (from ongoing stress) drives cortisol elevation, inflammation, and brain fog.
symptom cluster: A group of symptoms that tend to occur together, identified through statistical analysis. The 793-person Long COVID study found 6 distinct clusters with dramatically different PASC rates: physical+mental (85%) vs pure physical (51%).
theta rhythm: Brain waves in the 4-7 Hz frequency range, associated with drowsiness, cognitive slowing, and reduced information processing efficiency. Elevated theta power in brain fog patients correlates with subjective fatigue severity (Fabio 2024). Think of theta as your brain's 'buffering' indicator — when it's elevated, information processing is sluggish.
TIBC: Total iron-binding capacity — measures how much iron your blood can carry. High TIBC with low ferritin confirms iron deficiency, even when haemoglobin looks normal.
tilt table test: The gold standard diagnostic test for POTS. You lie on a table that tilts to 60-70 degrees while heart rate and blood pressure are monitored. A sustained HR increase of ≥30 bpm (≥40 in adolescents) within 10 minutes without significant BP drop confirms POTS.
TNF: Tumour necrosis factor-alpha — a pro-inflammatory cytokine. Elevated in chronic inflammation, obesity, and autoimmune disease. Impairs synaptic plasticity (the brain's ability to form new connections).
TPO: Thyroid peroxidase antibodies — elevated levels indicate Hashimoto's thyroiditis (autoimmune thyroid disease), one of the most commonly missed causes of brain fog. Can be elevated years before TSH becomes abnormal.
transcranial: Delivered through the skull to the brain — refers to non-invasive therapies like transcranial photobiomodulation (light) or transcranial direct current stimulation (electrical) that target brain tissue from outside.
TSH: Thyroid-stimulating hormone — the standard thyroid screening test. But TSH alone misses subclinical thyroid dysfunction. Always request Free T3, Free T4, and TPO antibodies alongside it.
UARS: Upper airway resistance syndrome — a sleep breathing disorder that causes brain fog and fatigue despite a 'normal' sleep study (normal AHI). Only detected when RERAs are scored. Ask your sleep lab specifically.
vagal: Relating to the vagus nerve — the main nerve of the parasympathetic nervous system. Vagal tone refers to the activity level of this nerve. Higher vagal tone = better stress resilience and lower inflammation.
vagus nerve: The longest cranial nerve, connecting the brain to the gut, heart, and lungs. It controls the parasympathetic (rest-and-digest) nervous system. Stimulating it (cold exposure, deep breathing, gargling) reduces inflammation.
vestibular: Relating to the inner ear balance system. Vestibular dysfunction (from concussion, inner ear problems, or autonomic disorders) causes dizziness, spatial disorientation, and cognitive fog.
zonulin: A protein that regulates the tight junctions between gut lining cells. Gluten and certain bacteria trigger zonulin release, opening gaps in the gut wall (intestinal permeability) and allowing inflammatory molecules into the bloodstream.