To the best of our knowledge, this is the first study performed in China investigating initial asthma severity at diagnosis, and changes in severity over the first year of management. Our results showed that after 1 year nearly 10% of patients had moderate or severe asthma. Our study represents actual clinical practice in China of a heterogeneous adult and adolescent populations treated in both tertiary and secondary hospitals with a wide regional coverage. The results of our study spotlight real-world management of asthma, and complement previous data from cross-sectional population-based surveys.
Unlike other chronic diseases, there are no objective markers of underlying asthma disease severity; however, asthma severity can be assessed when a patient has been on controller treatment for several months. In this study that included 7,654 newly diagnosed asthma patients, the prevalence of severe asthma was stable during a 1-year follow-up period. Our result of a frequency of 2.7% of patients having severe asthma at 1 year is similar to that of 2.4% reported in a retrospective study performed in Japan that used a nationwide health care claims database , but somewhat lower than the commonly reported prevalence of 5–10% [15, 16]. In a prior cross-sectional study in China , the investigators used different criteria for determining asthma severity that what was used in our study . Data used in our study were obtained from continuous outpatient records, and there were no lapses of treatment or missing data with respect to any of our included patients.
Population-based studies and longitudinal studies in other countries help in understanding changes in asthma over time and associations with initial disease severity. A cross-sectional survey of 3,509 children aged 5–14 years living in rural and urban regions of Canada found a difference in childhood asthma prevalence between urban and rural locations, and once a child has asthma certain rural exposures may aggravate the disease . A population-based survey of over 12,000 adolescents in France showed that the prevalence of 'ever asthma' was higher among boys, whereas severe asthma was associated with early onset and female sex . Important for the allocation of health care resources, the authors found that asthmatic adolescents required more health care in terms of medication use, consultations and hospitalizations other than for asthma than other adolescents, and this relation was strongest among severe asthmatics. A Danish study followed asthmatics for over 30 years, and reported that female sex, previous severe exacerbation(s), and older age at baseline were associated with uncontrolled asthma at follow-up, and a blood-eosinophil count ≥ 0.3 × 109L and being prescribed an ICS at baseline were associated with being prescribed a medium- or high-dose ICS at follow-up . The authors concluded that asthma rarely remits in adults, especially in individuals with longer duration and more severe disease, and worse initial disease is associated with uncontrolled asthma at follow-up.
GINA guidelines provide specific recommendations for choices of pharmacotherapy and frequency of regular follow-up for monitoring asthma control and adjusting therapy as needed. However, in many cases the goals of an individual patient will differ from medical goals. Poor adherence to therapy is common in patients with asthma, and is often associated with increased use of health care resources, morbidity, and mortality, and this includes patients in China with asthma [21, 22]. A clear explanation of asthma and disease severity by a physician can improve a patient’s trust and confidence in treatment. Asthma severity is not a static feature and may change overtime, and in our study approximately 90% of patients had mild asthma at 12 months, even though a marked proportion of patients had moderate or severe asthma during the first 6 months. Importantly our results showed that in general patients diagnosed initially with mild asthma tended to continue to have mild asthma and not progress in disease severity.
Our results showed that a small group of patients developed severe asthma over the year, and some patients with severe asthma did not have a reduction in severity over the year. As such, further study is needed to examine the clinical features of newly diagnosed patients with severe asthma who do not experience a reduction in severity in order to target these patients for more intensive treatment and reduce the disease burden.
There are both strengths and weaknesses of using a health information database. One of the main advantages is that it provides health care data from a large number of people. Another advantage is that all outpatient visits and hospitalizations can be identified. This allows follow-up of individual patients; most epidemical studies are cross-sectional without follow-up data. These advantages enabled the research to determine the reality of asthma management, and complement the limitations of previous studies performed in a hospital-based setting. Furthermore, our study only included individuals who were actively engaged with their health care providers, i.e., we only included individuals who had been in regular contact with the health care system for ailments other than asthma before the index date. By doing so, we minimized the frequency of patients that may have been lost to follow-up for various reasons, such as loss of health insurance coverage.
On the other hand, there are limitations inherent is studies that are based on data from medical records. Data retrieval is limited to the variables registered in the database, and medication use is based on medications prescribed and this does not necessarily reflect how patients actually use their medications. Our study classified asthma severity according to medications prescribed, not clinical data, and did not assess medication adherence. These shortcomings may have resulted in the misclassification of asthma severity in some patients. In addition, using asthma medications as a proxy for asthma severity relies on physician adherence to current practice guidelines . Deviation of asthma treatment from guidelines may result in inaccurate estimations of asthma severity and other potential biases .