*4.4. Identified Research Gaps*

Based on the results obtained, we have identified certain research gaps. Even though understanding of the pathogenesis of asthma has been extensively studied, the association between asthma and environmental factors deserves more attention from researchers. Asthma has been long recognized as a chronic condition and with the proper treatment and management, the symptoms can be well controlled and asthma patients are able to live a full and rewarding life [5]. Nevertheless, under the influence of continuously worsening air quality, it is undeniable that asthmatics have become more and more vulnerable [50–53]. Increased levels of ambient ozone, nitrogen dioxide (NO2), sulfur dioxide (SO2) and particulates (PM2.5, PM10) were proved to be associated with higher prevalence of asthma and symptoms onset, as well as increased hospital admission due to asthma attack [54]. Children and adolescents with asthma are particular susceptible to these pollutants due to their underdeveloped lung function and immature metabolic pathways [51,55–57]. The current environmental situation has showed little sign of improvement and has continued to bring about detrimental effects on health-related quality of life of asthma patients, suggesting the need for further update research on this topic.

In the meanwhile, notwithstanding the fact that asthma is a chronic condition with both direct and indirect cost, the financial burden of asthma is not among the emerging research domains identified in this study. According to the Global Asthma Report 2018, annual direct cost per patient ranged from under USD 150 in United Arab Emirates to more than USD 3000 in USA and, at national level, total annual costs for asthma in the USA witnessed an increase of 3 billion USD from 2002 to 2011. Total costs for asthma patients aged 15 to 64 in Europe were USD 24.7 billion during 1999–2002, in which the United Kingdom itself accounted for USD 9.8 billion [4]. The data indicates that asthma is an economic burden even for high-income countries. While indirect costs are regularly ignored by cost estimates, studies have consistently indicated that indirect costs constitute a significant part of the economic

burden of asthma [58–60]. On the other hand, high cost of treatment can be regarded as an important limiting factor for improving quality of life of asthma patients in developing countries. While access to inhaled corticosteroids has been recognized as one of the keys to improve quality of life among asthmatics, for many asthma patients in developing countries, such as India, Malaysia and Thailand, inhaled corticosteroids are either inaccessible or unaffordable [4,61,62]. In Indonesia, although inhaled corticosteroid is available and covered by health insurance, many people are unable to afford a spacer, which is the best delivery system for the drug [4]. Therefore, there presents a call for more research on the economic aspects of asthma.
