Since 1990, the global prevalence of asthma in children and adults has increased significantly. These trends are reflected in the results of major asthma surveys such as the International Study of Asthma and Allergies in Childhood (ISAAC) and the European Community Respiratory Health Survey (ECRHS).
Asthma is a public health concern for all countries because, without proper management, asthma can result in frequent emergency room (ER) visits, hospitalisations, and premature deaths. However, in the last decade, lifetime and 12-month diagnosed prevalence of asthma have stabilised; it is unclear if this is due to progress stalling in diagnosis efforts, or because the true prevalence of asthma is levelling out.
GlobalData’s epidemiology forecast of asthma shows that in the last decade, the lifetime (cases that have ever been diagnosed with asthma by a physician) and 12-month diagnosed prevalence (cases that have been diagnosed with asthma by a physician in the last 12 months) of asthma have plateaued in the seven major markets (7MM: US, France, Germany, Italy, Spain, UK, and Japan) (Figure 1).
GlobalData does not expect the diagnosed prevalence of asthma to increase significantly from 2019 to 2029. One reason why the diagnosed prevalence of asthma may have stabilised in the 7MM is that the diagnosis rate has not increased. It is possible that previous increases in the prevalence of asthma were driven by both a true increase in the prevalence of the disease due to increased air pollution and other risk factors and by better disease awareness leading to more cases being diagnosed by physicians.
The plateau of diagnosed prevalence observed in GlobalData’s analysis may indicate that in recent years the diagnosis rate of asthma has not increased, therefore the diagnosed prevalence has remained largely unchanged. Improved asthma management for diagnosed cases may also explain the stabilising patterns in the prevalence of asthma, particularly when looking at 12-month diagnosed prevalence because effective disease management would translate into a decreased chance of experiencing an asthma attack in the last 12 months. While proper disease management is not likely to influence estimates of lifetime diagnosed asthma, proper control of symptoms would result in fewer attacks.
Another factor may be limitations of the tests used to diagnose asthma in primary care settings leading to slower improvements in diagnosis. The three main tests for asthma are peak flow, spirometry, and FeNo (fractional exhaled nitric oxide). The peak flow test is commonly used, but it can cause over, under or misdiagnosis.
However, few primary care services have the facilities or trained staff to conduct spirometry or FeNo tests. Spirometry testing can take several follow-up appointments to conduct. While the current evidence suggests lifetime and 12-month diagnosed prevalence are stabilising, the real reason is not known.
The current Covid-19 pandemic has interrupted primary care services and consequently, the diagnosed prevalence of asthma will temporarily decrease further as more cases are likely to go undiagnosed and untreated. However, continuing to foment disease awareness among physicians and in the community will have a positive effect on diagnosis rates. This is critical because lifetime and 12-month diagnosed prevalent cases are expected to increase, even if prevalence rates remain stable, because of population growth in the 7MM.
Figure 1: 7MM, Lifetime and 12-Month Diagnosed Asthma Prevalence (%), Men and Women, All Ages, 2009–2029.