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Medicine
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Not a fact anymore
Every patient having a heart attack should receive supplemental oxygen, even when blood oxygen is normal.
What we know now
Routine oxygen is not recommended for heart-attack patients who are not hypoxemic. Oxygen remains appropriate when saturation is low or respiratory distress is present.
- Status
- Narrowed
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- 1970s–2010s
Not a fact anymore
A concussion should be treated with prolonged complete physical and mental rest until every symptom disappears.
What we know now
A brief period of relative rest is usually followed by a gradual return to ordinary activity below the level that substantially worsens symptoms. Prolonged strict rest can delay recovery.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈31 years
- Changed approximately
- 2010s–present
Not a fact anymore
Every case of appendicitis requires immediate removal of the appendix.
What we know now
Appendectomy remains a standard and highly effective treatment, but selected patients with imaging-confirmed uncomplicated appendicitis can be managed initially with antibiotics, accepting a meaningful risk of recurrence or later surgery.
- Status
- Narrowed
- Category
- Medicine
- Accepted for
- ≈120 years
- Changed approximately
- 2010s–present
Not a fact anymore
Urine in a healthy bladder is sterile, and any bacteria detected there indicate contamination or infection.
What we know now
Healthy bladders can contain low-biomass microbial communities. Detecting bacteria does not by itself establish a urinary tract infection.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈162 years
- Changed approximately
- 2010s
Not a fact anymore
Healthy lungs are sterile and contain no microbial community.
What we know now
Healthy lungs are not completely sterile. The lower airways contain small numbers of microbes, forming a low-density microbiome shaped by inhaled organisms, tiny amounts of material entering from the mouth and throat, immune clearance, and local conditions.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈125 years
- Changed approximately
- 2010s
Not a fact anymore
Adult human heart-muscle cells are permanently post-mitotic and are never replaced.
What we know now
Adult human heart-muscle cells, called cardiomyocytes, do renew, but very slowly. Estimates suggest that roughly 1% are replaced each year in younger adults, with the rate falling with age. That is far too little to rebuild the large amount of muscle lost in a major heart attack.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- Late 20th century–2000s
Not a fact anymore
Brown adipose tissue was thought to disappear after infancy or to have little physiological importance in normal adults.
What we know now
Many adults retain metabolically active brown adipose tissue, especially around the neck and upper chest. Its amount and activity vary with age, temperature, body composition, and other factors.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- 2000s
Not a fact anymore
Bone is primarily a structural and mineral-regulating organ, not an endocrine organ that signals to distant tissues.
What we know now
Bone is not only structural tissue. It is constantly rebuilt, stores and releases minerals, produces blood cells in its marrow, and also sends chemical signals to distant organs. One well-established example is FGF23, a hormone made mainly by bone cells that helps the kidneys control phosphate and vitamin D.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- Late 20th century–2000s
Not a fact anymore
The human appendix is a useless vestigial organ with no biological function.
What we know now
The appendix contains abundant immune tissue and may help maintain or restore gut microbial communities. It is not essential, and most people can live normally after it is removed.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈122 years
- Changed approximately
- Late 20th century–present
Not a fact anymore
Menopausal hormone therapy prevents cardiovascular disease in generally healthy postmenopausal women.
What we know now
Systemic menopausal hormone therapy should not be started solely to prevent cardiovascular disease. Benefits and risks differ by age, time since menopause, formulation, route, dose, and whether a uterus is present.
- Status
- Narrowed
- Category
- Medicine
- Accepted for
- ≈17 years
- Changed approximately
- 1998–2002
Not a fact anymore
Prescribed bed rest prevents preterm birth and other common pregnancy complications.
What we know now
Routine activity restriction has not been shown to prevent preterm birth and can cause deconditioning, bone loss, psychosocial harm, financial disruption, and increased risk of blood clots.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈145 years
- Changed approximately
- 1990s–2010s
Not a fact anymore
A high systolic blood pressure in an older adult is a harmless and necessary consequence of aging.
What we know now
Isolated systolic hypertension is a major, treatable risk factor for stroke, heart disease, kidney disease, and death. Treatment targets must still account for frailty, adverse effects, and individual circumstances.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈76 years
- Changed approximately
- 1970s–1990s
Not a fact anymore
Acute low-back pain is best treated with prolonged bed rest.
What we know now
For most uncomplicated acute low-back pain, prolonged bed rest provides no advantage and can delay recovery. Patients are generally encouraged to remain active as tolerated while serious causes are assessed when warning signs are present.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈140 years
- Changed approximately
- 1980s–1990s
Not a fact anymore
Suppressing premature ventricular beats after a heart attack reduces the risk of sudden death.
What we know now
After a heart attack, eliminating premature ventricular beats on an ECG does not necessarily make a patient safer. In the CAST trial, the drugs encainide and flecainide suppressed these abnormal beats but increased deaths from arrhythmia and increased overall mortality.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈14 years
- Changed approximately
- 1989
Not a fact anymore
Newborn babies do not feel pain in the same meaningful way as older children and adults.
What we know now
Newborns have functional pain pathways and show hormonal, physiological, behavioral, and neurological responses to painful procedures. Pain relief is an important part of neonatal care.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈102 years
- Changed approximately
- 1980s–1990s
Not a fact anymore
Beta blockers are dangerous and should not be used in patients with chronic heart failure.
What we know now
Selected beta blockers are standard treatment for stable heart failure with reduced ejection fraction, meaning the heart pumps out a smaller-than-normal share of the blood in its main chamber with each beat. When introduced carefully, these drugs reduce hospitalization and improve survival.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈20 years
- Changed approximately
- 1980s–2000s
Not a fact anymore
Body fat is an inert storage depot whose only important role is holding excess energy.
What we know now
Adipose tissue is metabolically active and functions as an endocrine and immune organ. It secretes hormones and signaling molecules that influence appetite, insulin sensitivity, inflammation, reproduction, and vascular biology.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈60 years
- Changed approximately
- 1980s–2000s
Not a fact anymore
Routine episiotomy prevents severe tearing, protects the pelvic floor, and improves childbirth outcomes.
What we know now
Routine episiotomy does not provide those broad benefits and can increase pain, blood loss, healing problems, and serious perineal injury. Restrictive use produces better outcomes for most spontaneous vaginal births.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈69 years
- Changed approximately
- 1980s–2000s
Not a fact anymore
Cervical cancer is unrelated to viral infection.
What we know now
Nearly all cervical cancers are caused by persistent infection with high-risk types of human papillomavirus, or HPV. HPV is very common and most infections clear on their own, but some high-risk infections persist and can gradually disrupt the controls that keep cervical cells from growing abnormally.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈33 years
- Changed approximately
- 1980s–1990s
Not a fact anymore
Peptic ulcers are primarily caused by stress and lifestyle.
What we know now
Most peptic ulcers are caused either by infection with Helicobacter pylori, a bacterium that can live in the stomach, or by nonsteroidal anti-inflammatory drugs (NSAIDs), a common class of pain-relief medicines that can damage the stomach and duodenal lining.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈32 years
- Changed approximately
- 1982–1990s
Not a fact anymore
Transmissible infectious agents were expected to require DNA or RNA to store and propagate biological information.
What we know now
Prions are infectious agents made mainly of protein and carry no DNA or RNA genome of their own. A misfolded prion protein can force normally folded copies of the same protein in the host to change into the same abnormal shape, allowing the harmful form to spread.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- 1982–1997
Not a fact anymore
Schizophrenia is caused by dysfunctional parenting and contradictory family communication.
What we know now
Schizophrenia is a complex disorder involving genetic vulnerability, brain development, biology, and environmental risk factors. Family relationships do not create the disorder.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈35 years
- Changed approximately
- 1960s–1990s
Not a fact anymore
The most extensive possible mastectomy gives women with early breast cancer the best chance of survival.
What we know now
For many early breast cancers, breast-conserving surgery followed by radiation provides survival comparable to mastectomy. Removing additional muscle and tissue does not automatically improve cancer control.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈95 years
- Changed approximately
- 1970s–1980s
Not a fact anymore
Asthma is primarily a psychological or psychosomatic disorder.
What we know now
Asthma is a chronic inflammatory airway disease involving variable airflow obstruction and airway hyperresponsiveness. Stress and emotion can influence symptoms, but they are not the underlying cause of asthma.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈90 years
- Changed approximately
- 1950s–1990s
Not a fact anymore
Autism is caused by cold, emotionally distant parenting.
What we know now
Autism is a neurodevelopmental condition shaped strongly by genetics and early development. Parenting style does not cause it.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈20 years
- Changed approximately
- 1960s–1980s
Not a fact anymore
Diethylstilbestrol safely prevents miscarriage and other pregnancy complications.
What we know now
DES does not prevent miscarriage. Prenatal exposure can cause rare clear-cell cancers and reproductive abnormalities in exposed daughters and other health effects in exposed children.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈26 years
- Changed approximately
- 1953–1971
Not a fact anymore
A person recovering from a heart attack should remain on strict bed rest for several weeks.
What we know now
After an uncomplicated heart attack, patients are usually mobilized much earlier. Carefully prescribed activity and cardiac rehabilitation improve recovery and help prevent the harms of prolonged immobility.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈55 years
- Changed approximately
- 1950s–1980s
Not a fact anymore
Prefrontal lobotomy is a broadly effective and acceptably safe treatment for severe mental illness.
What we know now
Lobotomy causes irreversible brain injury and can produce profound changes in personality, motivation, cognition, continence, seizure risk, disability, and death. It has been abandoned as routine psychiatric treatment.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈30 years
- Changed approximately
- 1950s–1970s
Not a fact anymore
Wounds heal best when kept dry and exposed to the air so that a hard scab can form.
What we know now
Many wounds heal faster in a protected, appropriately moist environment. Moisture supports cell migration and tissue repair, while excessive dryness can slow healing.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈112 years
- Changed approximately
- 1960s–1990s
Not a fact anymore
Thalidomide is safe to use during pregnancy.
What we know now
Thalidomide is a powerful human teratogen. Exposure during sensitive stages of early pregnancy can cause severe limb, ear, eye, cardiac, and internal-organ defects, and pregnancy must be rigorously prevented during treatment.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈4 years
- Changed approximately
- 1961–1962
Not a fact anymore
The placenta is a complete barrier that protects the fetus from medicines, chemicals, and infections in the mother's blood.
What we know now
The placenta is a selective exchange organ, not an impermeable wall. It allows oxygen and nutrients to reach the fetus and waste products to leave, but many medicines, alcohol, environmental chemicals, antibodies, and some infections can also cross it or affect its function.
- Status
- Narrowed
- Category
- Medicine
- Accepted for
- ≈76 years
- Changed approximately
- 1940s–1960s
Not a fact anymore
The thymus is a useless vestigial organ, especially after childhood.
What we know now
The thymus is a training and selection site for developing T cells, immune cells that help coordinate and carry out targeted immune responses. It helps preserve cells that can respond to threats while eliminating or restraining many that react strongly against the body's own tissues. Its activity declines with age but does not become meaningless.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈111 years
- Changed approximately
- 1961–1970s
Not a fact anymore
Repeated insulin-induced comas have a specific therapeutic effect on schizophrenia.
What we know now
Insulin-coma therapy has no established specific benefit for schizophrenia and carries risks including seizures, prolonged coma, brain injury, metabolic complications, and death.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈25 years
- Changed approximately
- 1950s–1960s
Not a fact anymore
Repeated medical X-ray exposure causes no cumulative biological harm.
What we know now
X-rays are ionizing radiation: they carry enough energy to remove electrons from atoms and can therefore damage tissue and DNA. Radiation dose accumulates across exposures, although the risk from an individually justified modern diagnostic examination is usually small compared with its clinical benefit.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈35 years
- Changed approximately
- 1900s–1950s
Not a fact anymore
Rickets is caused primarily by infection or poor hygiene.
What we know now
Most nutritional rickets results from inadequate vitamin D, calcium, or phosphate. These shortages impair bone mineralization—the hardening of growing bone with calcium- and phosphate-rich mineral. Limited sunlight, diet, malabsorption, and some inherited disorders can all contribute.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈69 years
- Changed approximately
- 1910s–1930s
Not a fact anymore
Pellagra is an infectious disease that spreads among poor communities.
What we know now
Primary pellagra is caused by severe deficiency of niacin (vitamin B3) or of tryptophan, an amino acid the body can use to make niacin. It can also develop when illness or medication interferes with absorption or metabolism.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈30 years
- Changed approximately
- 1910s–1930s
Not a fact anymore
Scurvy is a putrid disease caused by corruption of the body, often promoted by damp, cold, inactivity, and unsuitable food.
What we know now
Scurvy is caused by severe vitamin C deficiency. Vitamin C is required for collagen synthesis and other biological functions, and adequate dietary intake prevents and cures the disease.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈257 years
- Changed approximately
- 1907–1932
Not a fact anymore
Yellow fever spreads mainly through direct contact with patients, clothing, bedding, and other contaminated objects.
What we know now
Yellow fever is a viral disease spread mainly by infected mosquitoes. In urban transmission, Aedes aegypti is the principal mosquito vector; contaminated clothing, bedding, and ordinary contact with patients are not the main route.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈150 years
- Changed approximately
- 1900–1901
Not a fact anymore
Beriberi is caused by an infectious agent or toxin associated with rice.
What we know now
Beriberi is caused by thiamine deficiency. It can damage the nervous system, the cardiovascular system, or both.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈12 years
- Changed approximately
- 1890s–1930s
Not a fact anymore
Malaria is caused by foul or unhealthy air rising from marshes.
What we know now
Malaria is caused by Plasmodium parasites and is usually spread through the bites of infected female Anopheles mosquitoes.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈2,297 years
- Changed approximately
- 1880s–1900s
Not a fact anymore
Tuberculosis is mainly an inherited constitutional disease rather than a contagious infection.
What we know now
Tuberculosis is caused by infection with Mycobacterium tuberculosis. Genetics and immune function affect who becomes infected or develops disease, but the bacterium is the necessary cause.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈97 years
- Changed approximately
- 1882 onward
Not a fact anymore
A properly healing wound should produce pus.
What we know now
Pus usually indicates an inflammatory response to infection or tissue destruction. Modern wound care aims to prevent or control infection rather than encourage suppuration.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈667 years
- Changed approximately
- 1860s–early 20th century
Not a fact anymore
Cholera is caused by poisonous miasma, or bad air, arising from filth and decay.
What we know now
Cholera is an intestinal infection caused by toxigenic strains of the bacterium Vibrio cholerae, usually acquired through contaminated food or water.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈39 years
- Changed approximately
- 1850s–1880s
Not a fact anymore
Breast milk is menstrual blood redirected to the breasts and transformed after childbirth.
What we know now
Milk is synthesized by mammary epithelial cells from nutrients and water supplied through the bloodstream, under hormonal regulation involving prolactin, oxytocin, estrogen, progesterone, and other signals. It is not transformed menstrual blood.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- 18th–19th centuries, with modern endocrine physiology later completing the explanation
Not a fact anymore
Illness is caused by an imbalance among the body's four humors: blood, phlegm, yellow bile, and black bile.
What we know now
Diseases have many distinct causes and mechanisms, including infections, genetic changes, immune dysfunction, nutritional deficiencies, environmental exposures, degeneration, and injury. The four humors are not anatomical substances whose balance governs health.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈1,650 years
- Changed approximately
- 17th–19th centuries
Not a fact anymore
Puerperal fever is not carried from patient to patient on doctors' hands, so hand disinfection is unnecessary.
What we know now
Puerperal fever is usually a bacterial infection. Doctors and other medical staff can carry infectious material between patients, making hand hygiene a basic part of infection prevention.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈32 years
- Changed approximately
- 1840s–1880s
Not a fact anymore
Nerves are hollow channels that transmit animal or psychic spirits between the brain and the body.
What we know now
Nerves are bundles of neuronal axons that transmit information through electrochemical signaling, including membrane action potentials and neurotransmission at synapses.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- 17th–18th centuries
Not a fact anymore
The lungs' primary function is to cool the heart and regulate its innate heat.
What we know now
The lungs' central physiological role is gas exchange: bringing oxygen into the blood and removing carbon dioxide. They also contribute to acid-base regulation, filtering, metabolism, and other functions, but they do not exist primarily to cool an innately hot heart.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- 17th–18th centuries
Not a fact anymore
A pregnant woman's intense sights, fears, desires, or imagination can physically mark or deform the developing fetus.
What we know now
Congenital anomalies arise from genetic, chromosomal, developmental, infectious, environmental, nutritional, metabolic, or other biological causes. A mother's visual impressions or imagination do not imprint corresponding physical shapes or marks on the fetus.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- 18th century
Not a fact anymore
Planetary and stellar configurations exert physical influences that can cause disease and should guide medical diagnosis, prognosis, and treatment.
What we know now
Disease arises through biological, genetic, environmental, behavioral, nutritional, toxic, traumatic, and social mechanisms. Planetary positions and zodiacal configurations do not exert clinically meaningful causal effects on disease or determine appropriate treatment.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- 17th–19th centuries
Not a fact anymore
A cataract is an abnormal membrane or material lying in front of an otherwise transparent crystalline lens.
What we know now
A cataract is an opacity of the eye's natural crystalline lens itself.
- Status
- Corrected
- Category
- Medicine
- Accepted for
- ≈1,555 years
- Changed approximately
- 1705–1716
Not a fact anymore
Imagination, reason, and memory are located in particular fluid-filled ventricles or 'cells' of the brain.
What we know now
Cognitive functions emerge from distributed and interacting neural networks in brain tissue. The cerebral ventricles are fluid-filled spaces that contain and circulate cerebrospinal fluid, not chambers housing mental faculties.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- 17th–18th centuries
Not a fact anymore
The pituitary gland drains mucus or phlegm from the brain into the nose.
What we know now
The pituitary is an endocrine gland that releases hormones regulating growth, reproduction, stress responses, thyroid and adrenal function, water balance, and other processes. It is not a drainage route for brain mucus.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈1,505 years
- Changed approximately
- 1655–1672
Not a fact anymore
Blood is continually produced in the liver, flows outward to the body's tissues, and is consumed rather than recirculated.
What we know now
The heart pumps blood through a closed circulatory system. Blood repeatedly travels through arteries, capillaries, and veins, carrying gases, nutrients, hormones, wastes, and immune cells.
- Status
- Superseded
- Category
- Medicine
- Accepted for
- ≈1,478 years
- Changed approximately
- 1620s–1660s
Not a fact anymore
The crystalline lens is the eye's primary organ of visual sensation.
What we know now
The lens refracts and focuses incoming light, but the retina is the light-sensitive neural tissue that detects photons and begins visual processing.
- Status
- Corrected
- Category
- Medicine
- Accepted for
- ≈1,433 years
- Changed approximately
- Late 16th–early 17th centuries
Not a fact anymore
Humans possess a rete mirabile, a vascular network at the base of the brain like the one described by Galen.
What we know now
A true carotid rete mirabile is present in some animal species but is not a normal structure of human anatomy.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- ≈1,393 years
- Changed approximately
- 1543
Not a fact anymore
The human liver is divided into five distinct lobes.
What we know now
Standard anatomical description recognizes four named anatomical lobes of the human liver: right, left, caudate, and quadrate. Modern surgical anatomy also divides the liver functionally into vascular segments.
- Status
- Corrected
- Category
- Medicine
- Accepted for
- ≈1,393 years
- Changed approximately
- 1540–1543
Not a fact anymore
The human uterus has seven chambers or cells, with different chambers associated with male, female, or intersex fetuses.
What we know now
The human uterus has a single main uterine cavity. Fetal sex is determined genetically at fertilization and is not determined by implantation in a particular side or chamber of the uterus.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- Early-to-mid 16th century
Not a fact anymore
The adult human lower jaw consists of two bones joined together at the chin.
What we know now
The adult human mandible is a single bone. It develops from two embryonic halves that normally fuse at the mandibular symphysis during the first year of life.
- Status
- Corrected
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- c. 1200 in medieval Islamic anatomy; later in Renaissance European anatomy
Not a fact anymore
Arteries normally carry pneuma or air rather than blood.
What we know now
Arteries carry blood away from the heart. Systemic arteries normally carry oxygenated blood, while pulmonary arteries carry deoxygenated blood to the lungs.
- Status
- Overturned
- Category
- Medicine
- Accepted for
- Not quantified
- Changed approximately
- 2nd century CE in Galenic physiology
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