Asthme: Diagnostic Symptomes Causes Facteurs aggravants de la crise

Asthma epidemiology Asthma is excessively common among the individuals (up to 10% in adults and 35% in children). Asthma is differently distributed in the world. Asthma incidence is 1%/y in average. Children are at greater risk of asthma than adults, which could be due to a cohort effect. Severe asthma is reported by 1-3% of the general population (children and adults respectively). Recent population-based data show that the asthma prevalence increase observed worldwide in the past 30 years has now stopped in industrialised countries. Such phenomenon has been paralleled by an increase in the use of asthma medications. The development and phenotypic expression of asthma depends on a complex interaction between genetic and environmental factors. Gene-environment interactions already in early life should be explored to understand asthma epidemiological evolution. The role of the environment in asthma: hypotheses and contradictions Three hypotheses are described to explain the relation between allergens and environmental co-factors and the onset of atopy: the hygiene hypothesis, the allergenic hypothesis, and the high exposure tolerance inducing a Th2 derived response with blocking IgG4 synthesis. None of these hypotheses have been confirmed. It seems thus difficult to give recommendations for primary prevention of allergic diseases until results of prospective studies allow to consider a more precise behaviour. In contrast, subjects sensitized and exposed to allergens present an increased risk to develop asthma or non specific bronchial hyperreactivity. Therefore, secondary prevention appears as an essential method for treatment of allergic disease, with clinical benefits on symptoms which have recently been demonstrated in a clinical study. Diagnosis of asthma in adult: Asthma is underdiagnosed in France. Asthma can often be diagnosed on the basis of symptoms, help by specific questions useful to consider the diagnosis. Measurement of lung function is important, for diagnosis, evaluation of the reversibility, the variability and the severity of bronchial obstruction. Indeed, patient with asthma may have a poor recognition of their symptoms and a poor perception of bronchial obstruction. Peak expiratory flow meter is an important aid in the diagnosis of asthma but measurements do not always correlate with other measurements of lung function. Allergic status and risk factors must be identified to control environmental exposure. Particularities of childhood asthma: Asthma is the most frequent respiratory chronic disease in children. Underdiagnosis is frequent, resulting in undertreatment. Elimination of alternative causes of wheezing is a key step of asthma diagnosis, especially in infants. Chest X-ray must be systematically performed. Therapy is guided by the evaluation of asthma severity and is based on inhaled corticosteroids. As far as possible, low doses of inhaled corticosteroids must be delivered to children. Inhalation techniques must be adapted to the age of children. Most of asthmatic infants will stop wheezing before school age. On the contrary, most of shool-age asthmatic children will be still symptomatic at adulthood.