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Asthma is a global health problem affecting around 300 million individuals of all ages, ethnic groups and countries. It is estimated that around 250,000 people die prematurely each year as a result of asthma. Concepts of asthma severity and control are important in evaluating patients and their response to treatment, as well as for public health, registries, and research (clinical trials, epidemiologic, genetic, and mechanistic studies), but the terminology applied is not standardized, and terms are often used interchangeably. A common international approach is favored to define severe asthma, uncontrolled asthma, and when the 2 coincide, although adaptation may be required in accordance with local conditions. A World Health Organization meeting was convened April 5-6, 2009, to propose a uniform definition of severe asthma. An article was written by a group of experts and reviewed by the Global Alliance against Chronic Respiratory Diseases review group. Severe asthma is defined by the level of current clinical control and risks as “Uncontrolled asthma which can result in risk of frequent severe exacerbations (or death) and/or adverse reactions to medications and/or chronic morbidity (including impaired lung function or reduced lung growth in children).” Severe asthma includes 3 groups, each carrying different public health messages and challenges: (1) untreated severe asthma, (2) difficult-to-treat severe asthma, and (3) treatment-resistant severe asthma. The last group includes asthma for which control is not achieved despite the highest level of recommended treatment and asthma for which control can be maintained only with the highest level of recommended treatment. [Copyright &y& Elsevier]

Background: Phase I of the International Study of Asthma and Allergies in Childhood (ISAAC) was designed to allow worldwide comparisons of the prevalence of asthma symptoms. In phase III the phase I survey was repeated in order to assess changes over time. Methods: The phase I survey was repeated after an interval of 5-10 years in 106 centres in 56 countries in children aged 13-14 years (n = 304 679) and in 66 centres in 37 countries in children aged 6-7 years (n=193 404). Results: The mean symptom prevalence of current wheeze in the last 12 months changed slightly from 13.2% to 13.7% in the 13-14 year age group (mean increase of 0.06% per year) and from 11.1% to 11.6% in the 6-7 year age group (mean increase of 0.13% per year). There was also little change in the mean symptom prevalence of severe asthma or the symptom prevalence measured with the asthma video questionnaire. However, the time trends in asthma symptom prevalence showed different regional patterns. In Western Europe, current wheeze decreased by 0.07% per year in children aged 13-14 years but increased by 0.20% per year in children aged 6-7 years. The corresponding findings per year for the other regions in children aged 13-14 years and 6-7 years, respectively, were: Oceania (-0.39% and -0.21%); latin America (+0.32% and +0.07%); Northern and Eastern Europe (+0.26% and +0.05%); Africa (+0.16% and +0.10%); North America (+0.12% and +0.32%); Eastern Mediterranean (-0.10% and +0.79%); Asia-Pacific (+0.07% and -0.06%); and the Indian subcontinent (+0.02% and +0.06%). There was a particularly marked reduction in current asthma symptom prevalence in English language countries (-0.51% and -0.09%). Similar patterns were observed for symptoms of severe asthma. However, the percentage of children reported to have had asthma at some time in their lives increased by 0.28% per year in the 13-14 year age group and by 0.18% per year in the 6-7 year age group. Conclusions: These findings indicate that international differences in asthma symptom prevalence have reduced, particularly in the 13-14 year age group, with decreases in prevalence in English speaking countries and Western Europe and increases in prevalence in regions where prevalence was previously low. Although there was little change in the overall prevalence of current wheeze, the percentage of children reported to have had asthma increased significantly, possibly reflecting greater awareness of this condition and/or changes in diagnostic practice. The increases in asthma symptom prevalence in Africa, Latin America and parts of Asia indicate that the global burden of asthma is continuing to rise, but the global prevalence differences are lessening. [ABSTRACT FROM AUTHOR]