Difficult-to-control asthma: epidemiology and its link with environmental factors

The aim of the present review was to discuss the epidemiology of inadequate asthma control with an examination of contributing environmental factors.

Despite advances in asthma therapies, a proportion of patients with asthma continue to have difficulty in gaining adequate asthma control. Asthma severity and control in childhood are of particular importance as they translate to asthma morbidity in adulthood. Children with comorbid severe allergic rhinitis were more likely to have uncontrolled asthma. Recent data suggest that mouse allergen, more so than cockroach allergen, may be the most relevant urban allergen exposure. Tobacco smoke exposure, even passive exposure, leads to increased asthma symptoms and decreased response to inhaled corticosteroids. Efforts to ban smoking in public places have resulted in promising asthma results for entire populations. Energy-saving efforts to tighten a home's air leaks can lead to increased indoor pollutant levels and, therefore, must be accompanied by efforts to reduce, filter, or exchange indoor pollutants. Obesity is independently associated with decreased asthma control. Furthermore, the detrimental effects of pollutant exposure are enhanced in an overweight individual with asthma.

Lack of asthma control can be because of a complex web of factors including adherence, intrinsic factors, and environmental exposures. Further research into intervention strategies is needed to achieve improved rates of asthma control.