In Canada, asthma is managed by pulmonologists. Asthma is a chronic inflammatory airway disease in which the bronchial tubes narrow, swell, and produce extra mucus in response to triggers, producing reversible airflow limitation. It affects approximately 262 million people worldwide and roughly 25 million Americans (about 1 in 13), with onset most commonly in childhood.
Asthma (ICD-10: J45) is a chronic inflammatory disorder of the lower airways characterised by three linked features: bronchial hyperresponsiveness to non-specific stimuli, reversible airflow limitation, and over time, airway remodeling with thickening of the smooth muscle and basement membrane. Type-2 (T2-high) inflammation driven by eosinophils, mast cells, IL-4, IL-5, IL-13, and IgE is present in roughly 50-70% of cases; the remainder are classified as T2-low and tend to be neutrophilic, obesity-related, or paucigranulocytic. Triggers ignite a cascade of bronchoconstriction, mucosal edema, and mucus hypersecretion that narrows the airway lumen and produces wheeze, dyspnea, chest tightness, and cough. The condition spans a wide severity spectrum — intermittent, mild persistent, moderate persistent, and severe persistent — graded on symptom frequency, lung function, and treatment intensity required for control.
The key symptoms of Asthma are: Episodic wheeze — a high-pitched whistling sound on expiration that can also be audible on inspiration during severe attacks; classically intermittent and variable rather than constant., Shortness of breath that fluctuates with triggers, time of day, or exercise — not the steady progressive dyspnea typical of COPD or interstitial lung disease., Chest tightness described as pressure, banding, or an inability to take a full deep breath, often worse with cold air or exertion., Dry, non-productive cough that worsens at night or in the early hours of the morning, frequently waking the patient from sleep — sometimes the sole symptom (cough-variant asthma)., Symptoms triggered or worsened by viral upper respiratory infections, exercise, cold air, allergen exposure (dust mite, pollen, cats), tobacco smoke, strong odours, or NSAIDs in AERD., Diurnal variability — symptoms typically worse between 2 and 6 a.m. and on waking, mirroring the natural dip in cortisol and rise in vagal tone overnight., Rapid response to a short-acting bronchodilator within 5-15 minutes — partial reversibility distinguishes asthma from fixed airflow obstruction..
Diagnosis of asthma rests on a compatible clinical history of variable respiratory symptoms (wheeze, dyspnea, chest tightness, cough) together with objective evidence of variable expiratory airflow limitation. The cornerstone test is spirometry with bronchodilator reversibility: a post-bronchodilator increase in FEV1 of at least 12% and 200 mL after 400 micrograms of salbutamol confirms reversible airflow obstruction. A pre-bronchodilator FEV1/FVC ratio below the lower limit of normal (often quoted as <0.70 in adults or <0.75 below age 12) defines obstruction. When baseline spirometry is normal but symptoms persist, GINA 2024 and NICE NG244 (2024) recommend a bronchial provocation test — methacholine or mannitol — with a PC20 below 4 mg/mL or PD15 below 635 mg supporting the diagnosis. Fractional exhaled nitric oxide (FeNO) at or above 40 parts per billion in adults suggests T2-high airway inflammation and supports the diagnosis when added to spirometry; values between 25 and 40 are intermediate. Home or clinic peak expiratory flow variability greater than 10% in adults (over 13% in children) on twice-daily monitoring for 1-2 weeks also confirms variable airflow. Allergy testing (skin prick or specific IgE) is recommended in suspected allergic asthma to guide trigger avoidance and biologic selection. Differential diagnoses to exclude include COPD (irreversible obstruction in older smokers), vocal cord dysfunction (inspiratory stridor, normal spirometry), bronchiectasis, heart failure, and chronic rhinosinusitis with post-nasal drip. Children under 5 cannot perform reliable spirometry; diagnosis in this group is clinical with a trial of therapy and structured follow-up.
Asthma is a chronic but highly controllable disease. With correct inhaler use and adherence to a controller regimen, the great majority of patients live without symptom-limited activity, near-normal lung function, and rare exacerbations. Childhood asthma remits during adolescence in roughly 30-40% of children, persists into adulthood in another 30-40%, and recurs in about 20%; predictors of persistence include allergic sensitisation, severe early disease, and parental asthma. Adult-onset asthma is more often persistent and less likely to remit. Severe asthma affects 3-5% of asthmatics and historically carried a heavy oral steroid burden, but biologic therapy now allows around half of biologic-treated patients to stop or substantially reduce oral corticosteroids. Mortality has fallen by roughly 50% in high-income countries since the 1990s with inhaled corticosteroid adoption, although low- and middle-income countries still account for over 90% of the ~455,000 annual asthma deaths worldwide. The strongest individual prognostic factors are adherence to inhaled corticosteroids, correct inhaler technique, smoking status, and a written action plan.
Refer to a pulmonologist or asthma-trained allergist when the diagnosis is uncertain, when control remains poor despite Step 4 therapy with confirmed adherence and correct inhaler technique, when oral corticosteroids have been required two or more times in a year, when there is a history of a near-fatal attack, when occupational or aspirin-exacerbated phenotypes are suspected, or when a biologic is being considered. Children under 5 with persistent wheeze and severe asthma at any age also warrant specialist input. Most stable asthma is managed effectively in primary care if the action plan is in place and reviewed annually.
Find specialists →A mild-to-moderate exacerbation treated promptly with reliever therapy and a 5-7 day oral prednisone course typically resolves over 7-14 days, with peak flow returning to personal best by week 2-3. Severe exacerbations requiring hospital admission often need 4-6 weeks for full recovery, with airway hyperresponsiveness lingering for 6-8 weeks. New controller therapy reaches its full anti-inflammatory effect over 8-12 weeks; inhaled corticosteroid dose decisions should be made on at least 3 months of consistent use, not earlier. Biologic responses are reviewed at 4 months and again at 12 months — non-responders are switched to an alternative agent rather than continued indefinitely.
Regular aerobic exercise is safe and beneficial in well-controlled asthma; people with asthma should aim for 150 minutes of moderate-intensity activity per week. Warm up for 10-15 minutes to reduce bronchoconstriction risk, pre-treat with a SABA or ICS-formoterol 15 minutes before exercise if exercise-induced bronchoconstriction has been documented, and choose warm humid environments (swimming) over cold dry ones (running outdoors in winter, ice hockey) where possible. Children with asthma should not be restricted from sport — the evidence shows improved lung function and quality of life with regular activity.
Look for board certification in pulmonary medicine or allergy/immunology, regular use of spirometry and FeNO at the bedside, and access to a severe asthma multidisciplinary team with biologic prescribing authority. Ask whether the practice provides written personalised asthma action plans, whether they routinely check inhaler technique on every visit, and how they monitor oral corticosteroid exposure. Continuity matters — asthma is a long arc and inhaler regimens require iterative adjustment.
Medically reviewed by AIHealz Medical Editorial Board · May 12, 2026
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