Obesity, Air Pollution, and Epigenetic Modifications as Risk Factors for Asthma Phenotypes

Multiple interacting risk factors can influence the origin of asthma. Asthma is characterized by different clinical phenotypes, each of which includes different endotypes. There are four main clinical asthma phenotypes: (1) early-onset mild allergic asthma; (2) early-onset allergic moderate-to-severe remodeled asthma; (3) late-onset non-allergic eosinophilic asthma; and (4) late-onset non-eosinophilic non-allergic asthma. The main endotypes of asthma are T-helper (Th)-2 low and Th-2 high. The identification of asthma endotypes might help precision-based care move toward the personalized management of airway inflammation. In this scenario, it is important to know how the risk factors affect the pathophysiology of asthma. Accordingly, we focus our attention on the impact of obesity and air pollutants and how these risk factors together with epigenetic alterations influence the asthma phenotype/endotype and the pathogenesis of airway diseases. Our aim is to disseminate the progress of studies in this area by reporting recent observations on the topic. Finally, we believe that data/observations enclosed in this review suggest the need of further epidemiological studies to be useful to examine simultaneously the effect of more than one risk factor on clinical and biologic parameters of asthma.