Abstract and Introduction
Asthma management is in an intriguing phase, with acceptance of asthma as a heterogeneous condition with different phenotypes and underlying mechanisms and the potential for personalized asthma care, in parallel with increasing evidence about the population-level impact of basic strategies to increase access to medicines and improve inhaler technique and adherence. These changes have been facilitated by a more comprehensive view of evidence, including both randomized controlled trials with high internal validity and pragmatic and observational studies with high generalizability to patients in clinical practice. Evolving concepts of asthma control have led to new approaches to asthma assessment, recognizing the potential for discordance between symptom control and risk of exacerbations. A re-evaluation of evidence has also led to substantial changes in initial treatment of asthma, with the focus moving away from bronchodilator-only treatment, toward early use of inhaled corticosteroids and novel strategies for mild asthma. Sputum-guided treatment, where available, is successful in patients with moderate–severe asthma, but exhaled nitric oxide has not yet satisfied initial assumptions about its utility for biomarker-guided treatment. New interventions are emerging to improve adherence with asthma controller medications. A re-evaluation of evidence about written asthma action plans has led to encouragement of a rapid increase in controller dose, rather than relying on bronchodilator treatment and oral corticosteroids. Finally, new models of asthma care are emerging, utilizing the skills of allied health professionals and recognizing the potential role of telehealth.
The past 30 years have seen extraordinary changes in the approach to asthma management and in the impact of asthma on patients' lives. This is dramatically illustrated by the contrast between the admission in textbooks in the early 1980s that "the treatment of asthma is largely palliative," and the current perspective that good asthma control and minimal interference with daily life can be achieved for most patients with low daily doses of inhaled corticosteroids (ICSs) and minimal side effects. Over this period, mortality due to asthma has decreased substantially, with the Global Burden of Disease study reporting a global reduction in age-adjusted asthma mortality of 42% between 1990 and 2010.
Much of this change can be attributed to the dissemination and implementation of asthma management strategies, particularly with the broad uptake of ICS. Asthma guidelines for Australia were published in 1989, followed soon after by guidelines in the United States, United Kingdom, and Canada, and an international consensus document in 1992, the precursor to the first Global Initiative for Asthma (GINA) strategy report in 1995. These initial guidelines were consensus based, but by the mid-1990s, with the development of methodologies for evidence-based medicine at the McMaster University in Canada, guidelines development began to involve a review of evidence from scientific literature. Where evidence-based guidelines have been implemented extensively, substantial improvements in asthma outcomes have been seen. For example, provision of a free asthma service and medications in Brazil reduced asthma hospitalizations by 82%, and in Finland, a comprehensive 10-year country-wide approach to diagnosis, assessment, and treatment reduced hospitalizations by 69% and asthma costs by 36%.
Globally, however, the prevalence of asthma has increased in many countries, the burden of asthma has remained relatively unchanged, and key areas of need remain at both a patient and a population level. The most troubling of these are the gross global disparities still seen in access to health care and basic asthma medications, with years of life lost due to asthma still 20 times higher in low-income countries compared with high-income countries. Even in high-income countries, underdiagnosis and undertreatment of asthma are common, with contributory factors including the common perception of asthma as an acute intermittent condition and limited use of lung function testing, and, for those prescribed preventer inhalers, frequent problems with incorrect inhaler technique and poor adherence. Conversely, there are also well-recognized problems with overdiagnosis and overtreatment of asthma, with contributory factors including lack of diagnostic effort, misattribution of respiratory symptoms, and overprescribing. Around 3% of patients with asthma have severe disease, with persisting symptoms, exacerbations, and/or airflow limitation despite correct technique and good adherence with maximal conventional therapy;[9,10] this topic is dealt with in another article in this issue. Finally, for individual patients, a recent qualitative review has highlighted the emotional and social burdens of asthma, including those that carry through from childhood experiences to adulthood.
In considering these problems, and strategies that may help address them, it is apparent that some fundamental concepts underpinning evidence-based asthma management have been changing over the past 5 to 10 years. This article discusses some of these emerging concepts for adults and adolescents, starting with changes in perspectives about evidence-based medicine itself.
Semin Respir Crit Care Med. 2018;39(1):82-90. © 2018 Thieme Medical Publishers