Asthma: epidemiology, risk factors, and opportunities for prevention and treatment.

Asthma is characterised by variable airflow obstruction and is associated with symptoms of cough, wheeze, and dyspnoea, and with airway inflammation and hyperresponsiveness. There are approximately 300 million people with asthma worldwide. Despite a current plateau, the burden of this disease is likely to increase due to population growth, urbanisation, and ageing. Disease onset is associated with low birthweight, preterm birth, viral infections, in-utero passive smoke exposure, urbanisation, and occupational exposures. Obesity is associated with increased incidence and severity of asthma, whereas exposure to small allergen particles leads to severe disease. In adults and adolescents, inhaled corticosteroids in combination with formoterol (as anti-inflammatory reliever or as maintenance and anti-inflammatory reliever therapy) are widely recommended to control the symptoms of asthma. For children, low-dose inhaled corticosteroid is the preferred first-line treatment. Monotherapy with short-acting β-agonists is strongly discouraged. The WHO Global Action Plan for the Prevention and Control of Non-communicable Diseases includes availability of affordable combination inhalers for asthma. Co-ordinated national asthma policies, ensuring access to inhalers, have resulted in fewer hospitalisations and school and work absences. Future asthma prevalence could be reduced by good maternal and infant care, with reduction in premature births and reduction in infant respiratory infections, and by reduction in obesity at all ages.