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Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve after rest or sleep, or occurs independently of physical or mental exertion it may be a symptom of a medical condition that may become severe or progressive. Fatigue can be a feature of a mental disorder such as depression; may be associated with conditions of chronic pain such as
fibromyalgia Fibromyalgia (FM) is a medical condition characterized by chronic widespread pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sen ...

fibromyalgia
; it may also feature in conditions of chronic low-level inflammation, and be a disease-related symptom in many other conditions. Fatigue often has no known cause, and is recognised as being very complex in nature. Fatigability describes a susceptibility to fatigue. Physical fatigue results from
muscle fatigue Muscle fatigue is the decline in ability of muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ s ...
brought about by intense
physical activity Physical activity is defined as any voluntary bodily movement produced by skeletal muscles that requires energy expenditure.Global Recommendations on Physical Activity for Health, 2009. World Health Organization. Geneva, Switzerland. Accessed 13/07 ...
. Mental fatigue results from prolonged periods of cognitive activity which impairs cognitive ability. Mental fatigue can manifest as
sleepiness Somnolence (alternatively "sleepiness" or "drowsiness") is a state of strong desire for sleep, or sleeping for unusually long periods (compare hypersomnia). It has distinct meanings and causes. It can refer to the usual state preceding falling a ...
,
lethargy Lethargy is a state of tiredness, weariness, fatigue, or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overworking, stress, lack of exerc ...
, or
directed attention fatigue Directed attention fatigue (DAF) is a neuro-psychological phenomenon that results from overuse of the brain's inhibitory attention mechanisms, which handle incoming distractions while maintaining focus on a specific task. The greatest threat to a gi ...
. Mental fatigue can also impair physical performance.


Classification


Physical

Physical fatigue, or
muscle fatigue Muscle fatigue is the decline in ability of muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ s ...
, is the temporary physical inability of muscles to perform optimally. The onset of muscle fatigue during physical activity is gradual, and depends upon an individual's level of physical fitness – other factors include
sleep deprivation Sleep deprivation, also known as sleep insufficiency or sleeplessness, is the condition of not having adequate duration and/or quality of sleep Sleep is a Nature, naturally recurring state of mind and body, characterized by altered consciou ...
and overall health. Physical fatigue can be caused by a lack of energy in the muscle, by a decrease of the efficiency of the
neuromuscular junction A neuromuscular junction (or myoneural junction) is a chemical synapse Chemical synapses are biological junctions through which neuron A neuron or nerve cell is an electrically excitable cell that communicates with other cells via spe ...

neuromuscular junction
or by a reduction of the drive originating from the
central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecu ...

central nervous system
, and can be reversed by rest. The central component of fatigue is triggered by an increase of the level of
serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter Monoamine neurotransmitters are s and s that contain one group connected to an by a two-carbon chain (such as -CH2-CH2-). Examples are , and . All monoamines are ...

serotonin
in the central nervous system. During motor activity, serotonin released in synapses that contact
motor neuron A motor neuron (or motoneuron or efferent neuron) is a whose is located in the , or the , and whose (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly s and s. There are ...
s promotes
muscle contraction Muscle contraction is the activation of tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opposite of compression) * Tension (geology), a stress which stretches ...

muscle contraction
. During high level of motor activity, the amount of serotonin released increases and a spillover occurs. Serotonin binds to extrasynaptic receptors located on the
axonal initial segment An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences Despite the various English dialects Dialect The term dialect (from Latin , , from the Ancient Greek word , , "discourse", from ...
of motor neurons with the result that
nerve impulse In physiology, an action potential (AP) occurs when the membrane potential of a specific cell location rapidly rises and falls: this depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several type ...

nerve impulse
initiation and thereby muscle contraction are inhibited. Muscle strength testing can be used to determine the presence of a
neuromuscular disease A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron A motor neuron (or motoneuron) is a neuron A neuron or nerve cell is an electrically excitable cell that communicates with other cells via spe ...
, but cannot determine its cause. Additional testing, such as
electromyography Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles The skeleton refers to the frames of support of animal bodies. There are several different skeletal types: the exoskeleto ...
, can provide diagnostic information, but information gained from muscle strength testing alone is not enough to diagnose most neuromuscular disorders. People with
multiple sclerosis Multiple sclerosis (MS), also known as encephalomyelitis disseminata, is the most common demyelinating disease, in which the Myelin, insulating covers of nerve cells in the Human brain, brain and spinal cord are damaged. This damage disrupts the ...
experience a form of overwhelming lassitude or tiredness that can occur at any time of the day, for any duration, and that does not necessarily recur in a recognizable pattern for any given patient, referred to as "neurological fatigue", and often as "multiple sclerosis fatigue".


Mental

Mental fatigue is a temporary inability to maintain optimal cognitive performance. The onset of mental fatigue during any cognitive activity is gradual, and depends upon an individual's cognitive ability, and also upon other factors, such as sleep deprivation and overall health. Mental fatigue has also been shown to decrease physical performance. It can manifest as
somnolence Somnolence (alternatively sleepiness or drowsiness) is a state of strong desire for sleep Sleep is a Nature, naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, reduced m ...
,
lethargy Lethargy is a state of tiredness, weariness, fatigue, or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overworking, stress, lack of exerc ...
,
directed attention fatigue Directed attention fatigue (DAF) is a neuro-psychological phenomenon that results from overuse of the brain's inhibitory attention mechanisms, which handle incoming distractions while maintaining focus on a specific task. The greatest threat to a gi ...
, or disengagement. Research also suggests that mental fatigue is closely linked to the concept of
ego depletion Ego depletion refers to the idea that self-control Self-control, an aspect of inhibitory control, is the ability to regulate one's emotions, thoughts, and behavior in the face of temptations and impulses. As an executive function, self-control is ...
. For example, one pre-registered study of 686 participants found that after exerting mental effort, people are likely to disengage and become less interested in exerting further effort. Decreased attention can also be described as a more or less decreased
level of consciousness Level or levels may refer to: Engineering *Level (instrument), a device used to measure true horizontal or relative heights *Canal pound or level *Regrading or levelling, the process of raising and/or lowering the levels of land *Storey or level, ...
. In any case, this can be dangerous when performing tasks that require constant concentration, such as operating large vehicles. For instance, a person who is sufficiently somnolent may experience
microsleep Example of an EEG theta wave A microsleep (MS) is a sudden temporary episode of sleep Sleep is a Nature, naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, reduced mus ...

microsleep
. However, objective cognitive testing can be used to differentiate the neurocognitive deficits of brain disease from those attributable to tiredness. The
perception Perception (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the powe ...

perception
of mental fatigue is believed to be modulated by the brain's
reticular activating system The reticular formation is a set of interconnected Nucleus (neuroanatomy), nuclei that are located throughout the brainstem. It is not anatomically well defined, because it includes neurons located in different parts of the brain. The neurons of ...
(RAS). Fatigue impacts a driver's reaction time, awareness of hazards around them and their attention. Drowsy drivers are three times more likely to be involved in a car crash and if they are awake over 20 hours, is the equivalent of driving with a blood-alcohol concentration level of 0.08%.


Primary vs secondary

In some areas it has been proposed that fatigue be separated into primary fatigue, caused directly by a disease process, and secondary fatigue, caused by more general impacts on the person of having the disease.


Causes

Fatigue is a normal result of
work Work may refer to: * Work (human activity), intentional activity people perform to support themselves, others, or the community ** Manual labour, physical work done by humans ** House work, housework, or homemaking * Work (physics), the product of ...
, mental stress,
anxiety Anxiety is an emotion Emotions are mental state, psychological states brought on by neurophysiology, neurophysiological changes, variously associated with thoughts, feelings, behavioural responses, and a degree of pleasure or suffering, disp ...

anxiety
, overstimulation and understimulation,
jet lag Jet lag is a physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, including their ...
, active
recreation Recreation is an activity of leisure Leisure has often been defined as a quality of experience or as free time. Free time is spent away from , , , , and , as well as necessary activities such as and ing. Leisure as an experience usuall ...

recreation
,
boredom In conventional usage, boredom is an emotion Emotions are biological states associated with all of the nerve systems brought on by neurophysiological changes variously associated with thoughts, feelings, behavioural responses, and a degree ...

boredom
, lack of sleep or disease.


Acute

Causes of acute fatigue include
depression Depression may refer to: Mental health * Depression (mood), a state of low mood and aversion to activity * Mood disorders characterized by depression are commonly referred to as simply ''depression'', including: ** Dysthymia ** Major depressive ...
; chemical causes, such as
dehydration In physiology, dehydration is a lack of total body water In physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies ...

dehydration
,
poison In biology, poisons are Chemical substance, substances that can cause death, injury or harm to organs, Tissue (biology), tissues, Cell (biology), cells, and DNA usually by chemical reactions or other activity (chemistry), activity on the molecul ...

poison
ing,
low blood sugar Hypoglycemia, also known as low blood sugar, is a fall in blood sugar The blood sugar level, blood sugar concentration, or blood glucose level is the concentration of glucose present in the blood of humans and other animals. Glucose is a simpl ...
, or
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
or
vitamin A vitamin is an organic molecule , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's ability to Catenation, ...
deficiencies. Fatigue is different from
drowsiness Somnolence (alternatively "sleepiness" or "drowsiness") is a state of strong desire for sleep Sleep is a naturally recurring state of mind and body, characterized by altered consciousness , an English Paracelsian physician Consciousness, a ...
, where a patient feels that sleep is required. Temporary fatigue is likely to be a minor
illness A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting ...
like the
common cold The common cold, also known simply as a cold, is a viral infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (b ...
as one part of the
sickness behavior 350px, Ancher, Michael, "The Sick Girl", 1882, Statens Museum for Kunst Sickness behavior is a coordinated set of adaptation, adaptive behavioral changes that develop in illness, ill individuals during the course of an infection. They usually, but ...
response that happens when the
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as Tumor immunology, cancer cells and objects such ...
fights an
infection An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host A host is a person responsible for guests at an event or for providing hospitality during it. Host may ...

infection
.


Prolonged

Prolonged fatigue is a self-reported, persistent (constant) fatigue lasting at least one month.


Chronic

Chronic fatigue is a self-reported fatigue lasting at least six consecutive months. Chronic fatigue may be either persistent or relapsing. Chronic fatigue is a symptom of many diseases and conditions. Some major categories of conditions that feature fatigue include: *
Autoimmune disease An autoimmune disease is a condition arising from an abnormal immune response An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of differe ...

Autoimmune disease
s, PMCID: PMC6691096 such as
celiac disease Coeliac disease or celiac disease is a long-term autoimmune disorder, primarily affecting the small intestine, where individuals develop intolerance to gluten, present in foods such as wheat, rye and barley. Classic symptoms include gastrointe ...
,
lupus Lupus, technically known as systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary between people and may be mild to severe. Com ...

lupus
,
multiple sclerosis Multiple sclerosis (MS), also known as encephalomyelitis disseminata, is the most common demyelinating disease, in which the Myelin, insulating covers of nerve cells in the Human brain, brain and spinal cord are damaged. This damage disrupts the ...
,
myasthenia gravis Myasthenia gravis (MG) is a long-term neuromuscular disease A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron A motor neuron (or motoneuron) is a neuron A neuron or nerve cell is an electric ...
, Sjögren's syndrome, and
spondyloarthropathy Spondyloarthropathy or spondyloarthrosis refers to any joint disease An arthropathy is a disease of a joint. Signs and symptoms Arthralgia, Joint pain is a common but non-specific sign of joint disease. Signs will depend on the specific disease, ...
*
Anxiety disorder Anxiety disorders are a cluster of mental disorder A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such feat ...
s such as
generalized anxiety disorder Generalized anxiety disorder (GAD) is a mental Mental may refer to: * of or relating to the mind Films * Mental (2012 film), ''Mental'' (2012 film), an Australian comedy-drama * Mental (2016 film), ''Mental'' (2016 film), a Bangladeshi romantic ...

generalized anxiety disorder
*
Blood disorders Hematologic diseases are disorders which primarily affect the blood & blood-forming organs. Hematologic diseases include rare genetic disorders, anemia, HIV, sickle cell disease & complications from chemotherapy or transfusions. Myeloid * Hemoglob ...
such as
anemia Anemia (American and British English spelling differences#ae and oe, also spelled anaemia) is a decrease in the total amount of red blood cells (RBCs) or hemoglobin in the blood, or a lowered ability of the blood to carry oxygen. When anemia c ...

anemia
and
hemochromatosis Iron overload or haemochromatosis (also spelled ''hemochromatosis'' in American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varietie ...
*
Cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumor A benign tumor is a mass of cells Cell most often refers to: * Cell (biolo ...

Cancer
, in which case it is called
cancer fatigueCancer-related fatigue is a subjective symptom of fatigue (medicine), fatigue that is experienced by nearly all cancer patients. Among patients receiving cancer treatment other than surgery, it is essentially universal. Fatigue is a normal and expe ...
*
Chronic fatigue syndrome Chronic fatigue syndrome (CFS), also called myalgic encephalomyelitis (ME) and ME/CFS, is a complex, fatiguing, long-term medical condition diagnosed by required primary symptoms and criteria, and often involves a broad range of symptoms. Distingu ...
(CFS) *
Substance use disorder Substance use disorder (SUD) is the persistent use of drugs (including alcohol) despite substantial harm and adverse consequences. Substance use disorders are characterized by an array of mental/emotional, physical, and behavioral problems such as ...
s including
alcohol use disorder Alcoholism is, broadly, any drinking of alcohol (drug), alcohol that results in significant Mental health, mental or physical health problems. Alcoholism is not a recognized diagnostic entity. Predominant diagnostic classifications are alcoho ...
*
Depression Depression may refer to: Mental health * Depression (mood), a state of low mood and aversion to activity * Mood disorders characterized by depression are commonly referred to as simply ''depression'', including: ** Dysthymia ** Major depressive ...
and other mental disorders that feature
depressed mood Depression is a state of low Mood (psychology), mood and aversion to activity. It can affect a person's thoughts, behavior, motivation, feelings, and subjective well-being, sense of well-being. The core symptom of depression is said to be anh ...
*
Developmental disorder Developmental disorders comprise a group of psychiatric Psychiatry is the medical specialty A medical specialty is a branch of medical practice that is focused on a defined group of patients, diseases, skills, or philosophy. Examples include ...
s such as
autism spectrum disorder The autism spectrum encompasses a range of neurodevelopmental disorder, neurodevelopmental conditions, including autism and Asperger syndrome, generally known as autism spectrum disorders (ASD). Individuals on the autism spectrum typically exper ...
*
Eating disorder An eating disorder is a mental disorder defined by abnormal eating behaviors that negatively affect a person's health, physical or mental health, mental health. Only one eating disorder can be diagnosed at a given time. Types of eating disorders ...
s, which can produce fatigue due to inadequate nutrition *
Endocrine disease Endocrine diseases are disorders of the endocrine system The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant ta ...
s or metabolic disorders:
diabetes mellitus Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorders characterized by a hyperglycemia, high blood sugar level over a prolonged period of time. Symptoms often include frequent urination, Polydipsia, increased th ...
,
hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two ...

hypothyroidism
and Addison’s disease *
Fibromyalgia Fibromyalgia (FM) is a medical condition characterized by chronic widespread pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sen ...

Fibromyalgia
*
Gulf War syndrome #REDIRECT Gulf War syndrome Gulf War syndrome or Gulf War illness is a chronic and multi-symptomatic disorder affecting returning military veterans of the 1990–1991 Persian Gulf War. A wide range of acute and chronic symptoms have been linked t ...
*
Heart failure Heart failure (HF), also known as congestive heart failure (CHF) and (congestive) cardiac failure (CCF), is a set of manifestations caused by the failure of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in mo ...
*
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus ''Lentivirus'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, inc ...

HIV
* Idiopathic chronic fatigue (ICF), which is chronic fatigue with no known cause that does not meet
chronic fatigue syndrome Chronic fatigue syndrome (CFS), also called myalgic encephalomyelitis (ME) and ME/CFS, is a complex, fatiguing, long-term medical condition diagnosed by required primary symptoms and criteria, and often involves a broad range of symptoms. Disting ...
criteria *
Inborn errors of metabolismInborn errors of metabolism form a large class of genetic diseases involving congenital disorders of enzyme activities. The majority are due to defects of single genes that code for enzymes that facilitate conversion of various substances (substrate ...
such as
fructose malabsorption Fructose malabsorption, formerly named dietary fructose intolerance (DFI), is a digestive disorder in which absorption of fructose Fructose, or fruit sugar, is a simple ketonic simple sugar found in many plants, where it is often bonded to gluc ...
. *
Infectious diseases An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxin A toxin is a harmful substance produced within living cells ...
such as
infectious mononucleosis Infectious mononucleosis (IM, mono), also known as glandular fever, is an infection usually caused by the Epstein–Barr virus The Epstein–Barr virus (EBV), formally called ''Human gammaherpesvirus 4'', is one of the nine known human herpe ...
or
tuberculosis Tuberculosis (TB) is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to the in ...

tuberculosis
*
Irritable bowel syndrome Irritable bowel syndrome (IBS), referred to previously as spastic or nervous colon, and spastic bowel, is a functional gastrointestinal disorder Functional may refer to: * Movements in architecture: ** Functionalism (architecture) In archit ...

Irritable bowel syndrome
*
Kidney disease Kidney disease, or renal disease, technically referred to as nephropathy, is damage to or disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of i ...
s e.g.
acute renal failure Acute kidney injury (AKI), previously called acute renal failure (ARF), is a sudden decrease in kidney function that develops within 7 days, as shown by an increase in serum creatinine Creatinine ( or ; from el, κρέας, kreas, flesh) is a ...

acute renal failure
,
chronic renal failure Chronic kidney disease (CKD) is a type of kidney disease The kidneys are two reddish-brown bean-shaped organs found in vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukary ...
*
Leukemia Leukemia ( also spelled leukaemia and pronounced ), is a group of blood cancer Tumors of the hematopoietic and lymphoid tissues (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English ...

Leukemia
or
lymphoma Lymphoma is a group of blood cancer, blood malignancies that develop from lymphocytes (a type of white blood cell). The name often refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include Lymphadenopathy, ...

lymphoma
*
Liver failure Liver failure is the inability of the liver The liver is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs tha ...
or liver diseases e.g.
Hepatitis Hepatitis is inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogen In biology Biology is the natural science that studies life and living or ...

Hepatitis
*
Lyme disease Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the ''Borrelia'' bacterium which is spread by ticks in the genus ''Ixodes''. The most common sign of infection is an expanding red rash, known as erythema migrans ...
*
Neurological disorder A neurological disorder is any disorder of the nervous system In biology, the classical doctrine of the nervous system determines that it is a Complex system, highly complex part of an animal that coordinates its Behavior, actions and Sen ...
s such as
narcolepsy Narcolepsy is a long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank Consolidation", M. E. Sharpe, Inc., 2002 based in Green ...
,
Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a chronic condition, long-term neurodegeneration, degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disea ...
,
Postural Orthostatic Tachycardia Syndrome Postural orthostatic tachycardia syndrome (POTS) is a condition in which a change from lying A lie is an assertion that is believed to be false, typically used with the purpose of deceiving someone. The practice of communicating lies is c ...
and post-concussion syndrome *
Physical trauma Injury, also known as physical trauma, is damage Damage is any change in a thing, often a physical object, that degrades it away from its initial state. It can broadly be defined as "changes introduced into a system that adversely affect its ...
and other
pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain The International Association for the Study of Pain (IASP) is an international learned society A learned societ ...
-causing conditions, such as
arthritis Arthritis is a term often used to mean any disorder that affects joints A joint or articulation (or articular surface) is the connection made between bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of th ...
*
Sleep deprivation Sleep deprivation, also known as sleep insufficiency or sleeplessness, is the condition of not having adequate duration and/or quality of sleep Sleep is a Nature, naturally recurring state of mind and body, characterized by altered consciou ...
or
sleep disorder A sleep disorder, or somnipathy, is a medical disorder A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or ...
s, e.g.
sleep apnea Sleep apnea, also spelled sleep apnoea, is a sleep disorder A sleep disorder, or somnipathy, is a medical disorder of an individual's sleep patterns. Some sleep disorders are severe enough to interfere with normal physical, mental, social and ...
*
Stroke A stroke is a medical condition A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not due to any immediate external injury. Di ...

Stroke
*
Thyroid disease Thyroid disease is a medical condition that affects the function of the thyroid gland. The thyroid gland is located at the front of the neck and produces thyroid hormones that travel through the blood to help regulate many other organs, meaning t ...
such as
hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two ...

hypothyroidism
Fatigue may also be a side effect of certain
medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, therapy, treat, or preventive medicine, prevent disease. Drug therapy (pharmacotherapy) ...

medication
s (e.g.,
lithium salt Lithium compounds, also known as lithium salts, are primarily used as a psychiatric medication. They are primarily used to treat bipolar disorder and treat major depressive disorder Major depressive disorder (MDD), also known simply as dep ...
s,
ciprofloxacin Ciprofloxacin is an antibiotic used to treat a number of bacterial infections. This includes bone and joint infections, intra abdominal infections, certain type of infectious diarrhea, respiratory tract infections, skin infections, typhoid f ...

ciprofloxacin
);
beta blocker Beta blockers (beta-blockers, β-blockers, etc.) are a class of medications that are predominantly used to manage abnormal heart rhythms, and to protect the heart from a second heart attack (myocardial infarction A myocardial infarction (MI) ...
s, which can induce
exercise intolerance Exercise intolerance is a condition of inability or decreased ability to perform physical exercise Exercise is any bodily activity that enhances or maintains physical fitness Physical fitness is a state of health and well-being Well-be ...
; and many cancer treatments, particularly
chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment Cancer Cancer is a group of diseases A disease is a particular abnormal condition that negatively affects the structure or f ...

chemotherapy
and
radiotherapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that h ...
.


Inflammation

Inflammation has been linked to many types of fatigue. Findings implicate
neuroinflammationNeuroinflammation is inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune ...
in the
etiology Etiology (pronounced ; alternatively: aetiology or ætiology) is the study of causation or origination. The word is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ε ...
of fatigue in
autoimmune Autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other body normal constituents. Any disease that results from such an aberrant immune response is termed an "autoimmune disease An autoimmun ...
and related disorders.


Diagnosis

One study concluded about 50% of people who have fatigue receive a diagnosis that could explain the fatigue after a year with the condition. In those people who have a possible diagnosis, musculoskeletal (19.4%) and psychological problems (16.5%) are the most common. Definitive physical conditions were only found in 8.2% of cases. If a person with fatigue decides to seek medical advice, the overall goal is to identify and rule out any treatable conditions. This is done by considering the person's
medical history The medical history, case history, or anamnesis (from Greek: ἀνά, ''aná'', "open", and μνήσις, ''mnesis'', "memory") of a patient A patient is any recipient of health care services that are performed by Health professional, healthc ...
, any other symptoms that are present, and evaluating of the qualities of the fatigue itself. The affected person may be able to identify patterns to the fatigue, such as being more tired at certain times of day, whether fatigue increases throughout the day, and whether fatigue is reduced after taking a nap. Because disrupted sleep is a significant contributor to fatigue, a diagnostic evaluation considers the quality of sleep, the emotional state of the person, sleep pattern, and stress level. The amount of sleep, the hours that are set aside for sleep, and the number of times that a person awakens during the night are important. A
sleep studyA sleep study is a test that records the activity of the body during sleep. There are five main types of sleep studies that use different methods to test for different sleep characteristics and disorders. These include simple sleep studies, polysom ...
may be ordered to rule out a
sleep disorder A sleep disorder, or somnipathy, is a medical disorder A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or ...
.
Depression Depression may refer to: Mental health * Depression (mood), a state of low mood and aversion to activity * Mood disorders characterized by depression are commonly referred to as simply ''depression'', including: ** Dysthymia ** Major depressive ...
and other psychological conditions can produce fatigue, so people who report fatigue are routinely screened for these conditions, along with
substance use disorder Substance use disorder (SUD) is the persistent use of drugs (including alcohol) despite substantial harm and adverse consequences. Substance use disorders are characterized by an array of mental/emotional, physical, and behavioral problems such as ...
s, poor diet, and lack of
physical exercise Exercise is any bodily activity that enhances or maintains physical fitness Physical fitness is a state of health Health is a state of physical, mental and social well-being Well-being, also known as ''wellness'', ''prudential valu ...
, which paradoxically increases fatigue. Basic
medical tests A medical test is a medical procedure A medical procedure is a course of action intended to achieve a result in the delivery of healthcare. A medical procedure with the intention of determining, measuring, or diagnosing a patient condition or p ...
may be performed to rule out common causes of fatigue. These include
blood tests A blood test is a laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which or technological research, s, and may be performed. Laboratory services are provided in a variety of settings: ...
to check for infection or
anemia Anemia (American and British English spelling differences#ae and oe, also spelled anaemia) is a decrease in the total amount of red blood cells (RBCs) or hemoglobin in the blood, or a lowered ability of the blood to carry oxygen. When anemia c ...

anemia
, a
urinalysis Clinical urine tests are examinations of the physical Physical may refer to: *Physical examination, a regular overall check-up with a doctor *Physical (album), ''Physical'' (album), a 1981 album by Olivia Newton-John **Physical (Olivia Newton-John ...
to look for signs of
liver disease Liver disease (also called hepatic disease) is a type of damage to or disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements i ...
or
diabetes mellitus Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorders characterized by a hyperglycemia, high blood sugar level over a prolonged period of time. Symptoms often include frequent urination, Polydipsia, increased th ...
, and other tests to check for
kidney The kidneys are two reddish-brown bean-shaped organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly categorized ...

kidney
and
liver The liver is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's t ...

liver
function, such as a
comprehensive metabolic panel The comprehensive metabolic panel, or chemical screen, (CMP; CPT code 80053) is a panel Panel may refer to: Arts and media Visual arts * Panel (comics), a single image in a comic book, comic strip or cartoon; also, a comic strip containing o ...
. Other tests may be chosen depending on the patient's social history, such as an
HIV test HIV tests are used to detect the presence of the human immunodeficiency virus (HIV), the virus that causes AIDS, acquired immunodeficiency syndrome (AIDS), in blood serum, serum, saliva, or urine. Such tests may detect antibodies, antigens, or RN ...
or
pregnancy test A pregnancy test is used to determine whether a woman is pregnant Pregnancy, also known as gestation, is the time during which one or more offspring develops inside a woman. A multiple birth, multiple pregnancy involves more than one offspri ...

pregnancy test
.


Comparison with sleepiness

Fatigue is generally considered a more long-term condition than sleepiness (somnolence). Although sleepiness can be a symptom of a medical condition, it usually results from lack of restful sleep, or a lack of
stimulation Stimulation is the encouragement of development or the cause of activity generally. For example, "The press provides stimulation of political discourse." An interesting or fun activity can be described as "stimulating", regardless of its physica ...
. Chronic fatigue, on the other hand, is a symptom of a greater medical problem in most cases. It manifests in mental or physical weariness and inability to complete tasks at normal performance. Both are often used interchangeably and even categorized under the description of 'being tired.' Fatigue is often described as an uncomfortable tiredness, whereas sleepiness is comfortable and inviting.


Measurement

Fatigue can be quantitatively measured. Devices to measure medical fatigue have been developed by Japanese companies, among them
Nintendo is a Japanese Multinational corporation, multinational consumer electronics and video game company headquartered in Kyoto, Japan. The company was founded in 1889 as by craftsman Fusajiro Yamauchi and originally produced handmade playing ca ...

Nintendo
(cancelled). Nevertheless, such devices are not in common use outside Japan.


Management

Medications are reviewed as some have side effects that may contribute to fatigue and the interactions of medications are complex.


See also

* Cancer-related fatigue *
Combat stress reaction Combat stress reaction (CSR) is a term used within the military to describe acute behavioral disorganization seen by medical personnel as a direct result of the trauma of war. Also known as "combat fatigue" or "battle neurosis", it has some overla ...
*
Directed attention fatigue Directed attention fatigue (DAF) is a neuro-psychological phenomenon that results from overuse of the brain's inhibitory attention mechanisms, which handle incoming distractions while maintaining focus on a specific task. The greatest threat to a g ...
* Effects of fatigue on safety *
Gaucher's disease Gaucher's disease or Gaucher disease () (GD) is a genetic disorder in which glucocerebroside (a sphingolipid, also known as glucosylceramide) accumulates in cells and certain organs. The disorder is characterized by bruising, fatigue (medical), fati ...
*
Heat illness Heat illness is a spectrum of disorders due to environmental exposure to heat. It includes minor conditions such as heat cramps, heat syncope, and heat exhaustion as well as the more severe condition known as heat stroke. It can affect any or a ...
*
Malaise As a medical term, malaise is a feeling of general suffering, discomfort, uneasiness, or pain, and often the first sign of an infection or other disease. The word has existed in French language, French since at least the 12th century. The term i ...
*
Microsleep A microsleep (MS) is a sudden temporary episode of sleep or drowsiness which may last for a few seconds or up to several seconds where an individual fails to respond to some arbitrary sensory input and becomes unconscious.International Classific ...

Microsleep
*
Museum fatigue Museum fatigue is a state of physical or mental fatigue caused by the experience of exhibits in museums and similar cultural institutions. The collection of phenomena that characterize museum fatigue was first described in 1916, and has since rece ...
*
Presenteeism Presenteeism or working while sick is the act or culture of employees continuing to work as a performative measure, despite having reduced productivity levels or negative consequences. Reduced productivity during presenteeism is often due to illnes ...
* Sleep-deprived driving * Pacing (activity management) * Zoom fatigue


References


Further reading

Byung-Chul Han: ''Müdigkeitsgesellschaft''. Matthes & Seitz, Berlin 2010, . (Philosophical essay about fatigue as a sociological problem and symptom). * Danish edition: Træthedssamfundet. Møller, 2012, . * Dutch edition: De vermoeide samenleving. van gennep, 2012, . * Italian editions : La società della stanchezza. nottetempo, 2012, . * Korean edition: 한병철 지음 , 김태환 옮김. Moonji, 2011, . * Spanish edition: La sociedad del cansancio. Herder Editorial, 2012, .


External links


Fatigue — Information for Patients
U.S. National Cancer Institute {{Authority control Exercise physiology Symptoms Subjective experience