According to the Global Initiative for Asthma (GINA), asthma is a respiratory disease that can be diagnosed by a history of characteristic respiratory symptoms such as wheezing, shortness of breath, tightness of chest and a cough that varies in intensity over time, along with variable expiratory airflow limitation. Asthma is usually associated with a respiratory response to direct and indirect stimuli such as exercise, exposure to allergens, irritants, weather changes or viral respiratory infections and a chronic inflammatory process in both the small and larger airways. Symptoms and airflow limitation may vary in time and intensity and may disappear with adequate treatment. During physical examination, the degree of dyspnea is evaluated and attention is paid to a possible wheeze and prolonged expiration. Variability in airflow limitation can be demonstrated by spirometry and forms an important condition for diagnosing asthma. Airflow limitation shows reversibility, i.e. an FEV1 increase of >12% and 200 ml after using a bronchodilator during one visit, or variability, i.e. an increase in FEV1 >12% and 200 ml between two visits.
Asthma is called a heterogeneous disease because it has several different phenotypes, i.e. clusters of clinical and / or pathophysiological features, which may require different treatment strategies. The most common phenotype is allergic asthma, which is often diagnosed in childhood. Allergic asthma is characterised by eosinophilic airway inflammation and responds well to treatment with inhaled corticosteroids. In non-allergic phenotypes of asthma, symptoms and airflow limitation are not caused by allergens but by other stimuli, such as (eosinophilic) inflammation (which may often present in combination with nasal polyps), exercise induced asthma, late-onset asthma or asthma with obesity. In case of phenotypes with only little eosinophilic inflammation (such as asthma with obesity) patients may have a limited response to inhaled corticosteroids. Patients with long-standing asthma may develop a persistent airflow limitation, most likely due to airway remodelling. Asthma is usually diagnosed by the GP and managed in primary care.
Treatment is aimed at achieving good asthma control, tailored to personal treatment goals. In other words, as few symptoms and as few exacerbations as possible, no restrictions in activities, and normal participation in social life. Not smoking and having a smokefree environment are important measures against asthma. Inhaled medication is the basis of medication therapy and this includes inhaled corticosteroids (ICS) in most asthma phenotypes, which may or may not be combined with long-acting beta-2 agonists (LABA). With good asthma control in adults, the use of short-acting beta-2 agonists (SABA) is not usually necessary. SABA use is advised in children with frequent symptoms (and in children under six years of age with episodic expiratory wheezing but for who ‘asthma’ is usually not yet definitively diagnosed). LABA use in children with asthma, if necessary, is usually prescribed by a paediatrician or (paediatric) pulmonologist.
In ICPC-2, asthma is recorded as R96. The different phenotypes cannot be recorded separately within ICPC-2.
The mean incidence of asthma is 2.9 per 1000 patient years, which means that per 1000 patients in a year, three new diagnoses of asthma are made. Slightly more female than male patients are diagnosed (3.2 versus 2.5 per 1000 patient years). Incidence is highest in patients aged 0-4 years (3.6 per 1000 patient years), with more boys than girls being diagnosed (4.4 versus 2.8 per 1000 patient years). Incidence is lowest in patients older than 75 years. Link/Figure 1
The mean incidence of asthma in both men and women has gradually decreased in the period 2005-2021, and which is most apparent in children under five years of age (data from 2014-2021 is shown on the website, data from before 2014 is available upon request). This may be due to the advice in the most recent GP asthma guidelines to be cautious when diagnosing asthma in very young children.
The mean prevalence of asthma is 37.9 patients per 1000 patient years, meaning that among 1000 patients in a year, 38 patients have asthma and contact their GP for it over the course of that year. Mean prevalence is higher in female (41.6) than male patients (34.0 per 1000 patient years) and highest in patients between 45 and 74 years. From early childhood to puberty, prevalence is highest among male patients, whereas, from 15 years and upwards, the prevalence is highest in female patients. Due to the decreasing incidence of asthma, the prevalence of asthma has also somewhat decreased over time. Link/Figure 2
The higher prevalence when compared to incidence indicates that asthma is a chronic disease requiring the ongoing attention of the GP after the diagnosis has been made, often lasting many years.
The three most common initial symptoms presented as reasons for encounter (RFE) for asthma are shortness of breath (R02, in 27% of all episodes), a cough (R05, in 18%) and wheezing (R03, in 5%). Other common initial RFEs are a request for medication or the renewal of a prescription (*50, in 15%), as well as self-suspected asthma (R96, in 9%). Link/Table 3 RFEs do not differ significantly between women and men or between age groups.
In most episodes of asthma, regardless of sex and age, medication is prescribed (in 91% per year). Other common interventions are medical examination (*31, in 29%), health education (*45, in 22%) and a physical function test, most probably spirometry (*39, in 9% per year). Link/Table 4
The most prescribed medication is a selective beta-2 adrenoceptor agonist (R03AC, in 56% of episodes per year), followed by inhaled corticosteroids as a single inhaler (R03BA, in 36% per year) or as a combination device with a selective beta-2 adrenoreceptor agonists (R03AK, in 25% per year). Other medication, such as anticholinergics (5%), leukotriene receptor antagonists (2%) and antihistamines (4%) are prescribed less often. Link/Table 5
Referrals within primary care (*66, Link/Table 4) are rare (1% per year) and involve physical therapy in <1%, Link/Table 6) while referrals to a specialist (*67) occur in only 4% of the asthma episodes per year (most often to pulmonology and paediatrics). Link/Table 7 In children under five, the percentage of referrals is the highest (13%). Link/Table 8
Dutch guideline ‘Asthma in adults’: https://richtlijnen.nhg.org/standaarden/astma-bijvolwassenen#volledige-tekst (2020)
Dutch guideline ‘Asthma in children’: https://richtlijnen.nhg.org/standaarden/astma-bijkinderen#volledige-tekst (2022)
Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention, 2022. Available from: www.ginasthma.org