The epidemiology of asthma

Epidemiology, "the study of the distribution and determinants of disease frequency" (Hennekens, C. 1987: 3), encompasses three major components that are vital to the understanding of any medical condition. These three major components distribution, determinants and frequency emphasise that within the population, disease do not occur at random and they have causal and preventive factors that can be identified (Hennekens, C. 1987: 3). This is vital in the study of asthma.

Asthma, by definition, is "a chronic relapsing inflammatory disorder characterized by hyperactive airways, leading to episodic, reversible bronchoconstriction, owing to increased responsiveness of the trancheobronchial tree to various stimuli" (Cotran, R. 1999: 712). As one of the top national health priority areas, there has been much advances in our current understanding of asthma. However, there is still much we don't know. For instance, despite the definition above, it has been long debated that asthma is a syndrome as opposed to a disease, meaning that it is actually a group of disorders. Furthermore, although treatments such as inhalers are available, medical professionals have yet to discover a cure for asthma. Thus, in order to further our understanding of asthma, it is important to first examine the epidemiology of asthma.



As the majority of the population would know, asthma is a very common disease, particularly in childhood, creating a massive burden on a country's health system. However, if one requests statistics to discuss the epidemiology of asthma, it is rather difficult to arrive at a concrete number as the identification of patients suffering from asthma is rather ambiguous. Firstly, while it is easy to determine that a child frequently suffering from wheezes and constantly requires hospitalisation as an asthmatic, the majority of the cases lie between the two extremes. In comparing the prevalence of asthma between countries, research is often conducted with the definition being "recent wheezes" (Jalaludin, B.B. 2001: 110). It is with this definition in mind as we examine the epidemiology of asthma.



The International Study on Asthma and Allergies in Childhood discover that the highest prevalence of wheezes, at approximately 30%, within children is in developed nations such as the United Kingdom, United States, Australia,
Ireland and New Zealand. On the other side of the spectrum, countries with the lowest prevalence of wheezes are in developing nations such as China
and India. This finding has prompted scientists to propose the hygiene hypothesis which proposes that children growing up in a clean environment without exposure to environmental allergens are more likely to develop asthma than kids growing up in a "dirtier" environment.



Recent trends have shown a growing rise in the incidence of asthma over the past decade or so. A close examination on Victoria, for example, shows an increase of 141% of the last 26 years (Jalaludin, B.B.). Similar trends are seen in other developed nations. Although the prevalence of asthma in on the increase, the number of deaths each year contributed to asthma has fallen as scientists develop a better understanding of the condition. They've found out that although bronchodilators, such as salbutamol, should be used during an asthma attack, it is vital for the patient's health to continually and periodically use glucocorticosteroids as a preventive therapy. This discovery has managed to reduce the number of deaths by up to 80%.

In conclusion, examination of the epidemiology of asthma reveals many correlations between the disease itself and its various possible causes, some still yet to be explored. While some findings such as the hygiene hypothesis are merely hypotheses that require further research and understanding, other discoveries have led to monumental improvements in the current treatment for asthma. Thus, while the epidemiology of asthma seems at times to be only a bunch of numbers, it is important for asthma research.