Epidemiology has been defined as “the study of the distribution and determinants of disease frequency in human populations” . Its inherent assumption is that through systematic investigation of different populations or subpopulations in different places or at different times, causal and preventive factors of human disease can be identified. Thus, an essential task in epidemiology is first to quantify the occurrence of illness, i.e. its frequency and distribution within populations. Secondly, the goal is to evaluate hypotheses about the causation of disease by measuring the effects of people’s characteristics and their environment on the occurrence of illness. Thirdly, epidemiology has great potential to improve the understanding of disease mechanisms by longitudinally observing and meticulously describing different phenotypes of chronic diseases and their natural course from infancy over childhood and adolescence in adulthood. The advent of modern genetic tools has created a new field of genetic epidemiology, which attempts to tackle the many hurdles in deciphering the role of a subject’s genetic makeup in the development of chronic, multifactorial disease.
Asthma is a disease of the small airways of the lung that affects 155 million individuals in the world. Inflammation and intermittent constriction of these airways gives rise to symptoms of wheeze, cough, chest tightness and shortness of breath. Over time, the airways may become scarred and thickened, so that the airflow limitation may become permanent.
Asthma is the commonest chronic illness of childhood with a potential for lifelong symptoms. These two features and its substantial rise in prevalence over the past 30 years pose a number of challenges including identification of the underlying mechanisms and possible routes to prevention. The reasons for the increased prevalence remains obscure although several possibilities have been suggested, including dietary changes, increased exposure to allergens in the indoor environment and reductions in significant childhood infections. Important familial components have long been recognized and, although there is a great deal of interest in the genetic contributions to atopy and wheezing illnesses, there is little doubt that strong and recent environmental contributions have been responsible for what has been termed the “asthma epidemic”.
The appropriate treatment of asthma in childhood is based on an accurate diagnosis of the disease. The diagnosis of asthma can be made easily in children over 5 years of age on the basis of the definition of asthma as “an inflammatory disease of the airways leading to variable airway obstruction and presenting with wheeze, cough and dyspnea”. The diagnosis is difficult in younger children, mainly because it is difficult for them to cooperate in diagnostic procedures and the hesitation of physicians to perform certain procedures because of ethical and practical concerns. However, in order to improve quality of life, reduce health costs and establish early intervention strategies to avoid chronic pulmonary disease in later life, it is important to make the diagnosis of asthma as early in childhood as possible. Treatment strategies have progressed over the last decades from tertiary prevention and therapy to secondary prevention and therapy.
Asthma is a disease of the lung’s airways. It affects 155 million individuals in the world. Its prevalence and severity among children have increased significantly in the developed world over the past 40 years . It can be fatal, however, even if this were not a danger, its prevention would be important in order to improve quality of life, reduce health costs and establish early intervention strategies to avoid chronic pulmonary disease in later life. Airway inflammation and airway hyperresponsiveness are major pathophysiology characteristics of asthma that reflect various immune system reactions to diverse environmental factors.