Asthma

• 1. Introduction

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  Asthma announces itself with a sound. A wheeze. A cough in the early morning. A tightness in the chest that arrives at night and feels, to a child gasping in the dark, like being smothered. The word itself comes from the Greek for panting. In 2023 it reached an estimated 363 million people across the world and caused 442,000 deaths. Most of those deaths fell in low- and lower-middle-income countries. This is a disease with no known cure, yet one that can be controlled. So why do its airways close? Why does it favor boys in childhood and women in adulthood, cities over countryside, the poor in rich nations and the affluent in poor ones? And how did a condition recognized in ancient Egypt become, for a time, a problem doctors tried to treat by analyzing the soul?

• 2. Inside The Airways

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  Bronchial muscles spasm. The airways inflame, grow hypersensitive, and flood with mucus. These are the mechanisms beneath every asthma symptom. The disease mainly strikes the medium-sized airways, though small and large ones can join in as it progresses. Airway inflammation is present in everyone with asthma, even when no symptoms show.

  Eosinophils, neutrophils, CD4 T lymphocytes, mast cells, basophils, and macrophages all crowd into the inflamed tissue. Over time that inflammation reshapes the airway itself. The smooth muscle thickens. The tissue beneath the lining grows. More small blood vessels and nerve fibers appear, and the mucus-producing glands swell in size.

  Hyperresponsiveness is the heart of the trouble. The airways contract more than normal in response to triggers, and that overreaction makes the nerves in the airways more sensitive. Contraction of smooth muscle, swelling, a thickened wall, extra mucus, and mucus plugs all narrow the passage. Airway hyperresponsiveness is excessive narrowing in response to stimuli that should be harmless, and it is somewhat reversible with treatment.

• 3. Genes And Environment

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  Roughly half or more of asthma susceptibility is explained by genetics, according to twin and family studies. The disease is highly polygenic, built from hundreds of common and rare variants of small effect rather than a few powerful ones. Meta-analyses now report over 200 genome-wide significant susceptibility loci, many in immune and epithelial genes.

  The chromosome region 17q12-21 remains the most robustly replicated asthma locus, with its strongest effects on childhood-onset disease. Genes there, including ORMDL3 and GSDMB, appear to act through regulatory mechanisms, shaped by gene-environment interactions and early-life viral infections. Other loci cluster near IL33, TSLP, MHC class II, and GATA3, pointing toward type 2 inflammation and epithelial barrier function.

  Genetic correlation analyses reveal substantial overlap between asthma and other atopic disorders such as eczema and allergic rhinitis. Polygenic risk scores drawn from multi-ancestry studies can sort individuals by risk, predicting childhood-onset disease better than adult-onset. Those in the highest percentiles show several-fold increased odds of childhood asthma, though clinical use of these scores remains investigational.

• 4. What Sets It Off

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  Weight gain in the mother, a stressful pregnancy, smoking while pregnant, and caesarean section have all been linked to a child developing asthma. The reach extends back a generation. Children whose maternal grandmother smoked during pregnancy are more likely to develop asthma, regardless of whether their mothers smoked or had the disease. Nicotine is believed to drive these effects through changes in DNA.

  Urban environments carry higher rates than rural ones. Traffic pollution, secondhand smoke, social inequality, lack of green spaces, and industrialization concentrate in cities. Outdoor air pollution includes nitrogen dioxide, while indoor pollution ranges from asbestos and formaldehyde to mold, dust mites, cockroaches, and endotoxins. Rural settings, by contrast, offer cleaner air and early protective exposure to allergens and bacteria.

  The hygiene hypothesis turns intuition on its head. Severe and recurring respiratory infections in early childhood can lower lung function and lead to asthma. Yet certain childhood infections may lessen the risk of developing it. More than 400 occupational exposures have been linked to asthma, and unlike childhood asthma, which is more common in males, adult asthma is more prevalent in females.

• 5. When Asthma Attacks

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  Peak expiratory flow tells the story of an exacerbation. An attack brings rising shortness of breath, wheezing, coughing, and chest tightness alongside falling lung function. The body recruits accessory muscles, the sternocleidomastoid and scalene, to drag in air. The chest retracts with each breath, the skin and nails turn blue, and the heart races.

  A mild exacerbation drops peak expiratory flow by at least 20% over two days while daily activities grow difficult. In severe attacks, the person becomes restless and may struggle to speak as oxygen saturation falls and flow drops by more than half. Life-threatening exacerbations bring lethargy and a clouding of consciousness.

  Brittle asthma describes a pattern of recurrent, severe attacks. The term survives mainly in older medical literature. It is now best regarded as a historical descriptor rather than a distinct diagnosis, no longer routine in contemporary clinical practice.

• 6. Naming The Disease

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  Spirometry is the most accurate measurement of lung function. It tests how much air a person can forcefully exhale in one second, the FEV1, then compares that to the total exhaled after a deep breath. The test runs twice, once without medication and once after, and a rise in FEV1 after treatment points to asthma. No single test can confirm the diagnosis on its own.

  Global Initiative for Asthma guidelines ask doctors to confirm variable expiratory airflow in those with suggestive symptoms. When spirometry is unavailable, peak expiratory flow can be measured twice a day for two weeks, and daily changes greater than 10% may suggest asthma. Bronchial provocation testing uses inhaled methacholine, histamine, mannitol, or exercise to try to trigger airway narrowing, though a positive result alone does not confirm the disease.

  NICE guidelines for adults start with fractional exhaled nitric oxide and blood eosinophils. Children younger than five present a special case. Rather than testing them, guidelines recommend treating those with suggestive symptoms, and GINA sets three criteria all of which must be met, including confirmed wheezing in at least one episode.

• 7. Controllers And Relievers

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  Inhaled corticosteroids form the foundation. Asthma medications fall into three categories: controllers taken daily, relievers taken as needed for severe symptoms, and additional drugs for harder cases. Doses are kept as low as possible while still preventing exacerbations. It usually takes one or two weeks for symptoms to improve after starting inhaled corticosteroids.

  History reversed the order of treatment. Asthma was once managed with short-acting beta2 agonists as needed, with corticosteroids added only when symptoms persisted. Research showed that approach failed to prevent exacerbations, so guidelines now prefer inhaled corticosteroids over short-acting agonists. For teenagers and adults, the recommended first step is a combined inhaled corticosteroid and long-acting beta2 agonist inhaler.

  Salbutamol, also called albuterol, treats exacerbations in repeated doses every couple of hours until symptoms ease. When attacks are severe, oral corticosteroids continue for a week afterward, with oxygen therapy to hold saturation steady. For sensitized patients, allergen-specific immunotherapy slowly introduces the allergen by injection or under the tongue, while oral corticosteroids and bronchial thermoplasty wait as last resorts for severe asthma.

• 8. From Kyphi To Catecholamines

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  In ancient Egypt, asthma was treated by drinking an incense mixture known as kyphi. Hippocrates named it a specific respiratory problem around 450 BC, borrowing the Greek word for panting. By 200 BC it was thought to be at least partly tied to the emotions. In the 12th century the physician and philosopher Maimonides wrote his Treatise on Asthma in Arabic, describing the symptoms and stressing clean air and climate.

  Young Theodore Roosevelt, born in 1858, became one of the best-documented 19th-century cases. His youth was shaped by poor health and recurring nighttime attacks that felt as if he were being smothered to death, terrifying both the boy and his parents. At the time there was no effective treatment. One 1872 paper concluded asthma could be cured by rubbing the chest with chloroform liniment, and an 1880 treatment used intravenous pilocarpine.

  For a stretch of the 20th century, doctors looked inward. From the 1930s to the 1950s, asthma was counted among the holy seven psychosomatic illnesses, its cause considered psychological and its treatment often psychoanalysis. Analysts heard the asthmatic wheeze as a child's suppressed cry for its mother. The pharmacological story moved the other way. Epinephrine was first cited as a treatment in 1905, isoprenaline became the first pure beta-agonist synthesized in the 1940s, and the classification of beta1 and beta2 adrenergic receptors in 1967 opened the door to the selective beta2 agonists still in use.