How Much Asthma Is Atopic in Children?

Asthma is the most common chronic childhood disease worldwide and poses a significant health and socioeconomic burden. The prevalence of this disease differs geographically and seems on the rise in many parts of the world. (1). Cross-sectional and longitudinal studies have identified several indicators associated with high risk of asthma (2). Personal history of atopy in early life seems to be one of the key factors of an individual’s risk of persistent asthma. Indeed, numerous studies have demonstrated that early and multiple allergic sensitization (AS) specific to aeroallergens and some food antigens places a strong risk for the development of asthma in children (2–6). Atopic asthma represents the most common form of asthma in the pediatric age and is characterized by eosinophilic airway inflammation associated with specific immunoglobulin E (IgE) antibodies sensitization to various allergens, as evidenced by serology or skin prick test (7). According to a large population survey, including data from people aged 6–59 years (the Third National Health and Nutrition Examination Survey), 56.3% of asthma cases in the United States were attributable to atopy (8). Similarly, the 14-year follow-up analysis of an Australian community-based birth cohort showed that the proportion of asthma associated with atopy was 52% overall (9). The results of a recent cohort study, which followed a large group of newborns over various periods, indicated that the prevalence of asthma from 4 to 16 years is markedly higher among ever-allergic sensitized children compared to never-sensitized ones (10). At a population level, a recently published longitudinal study that prospectively collected data over the first four decades of life showed that the occurrence of asthma before the age of 13 years was more strongly associated with atopy and greater airflow obstruction than later onset asthma (11). Nevertheless, there is still controversy about the causal relationship between atopy and asthma, as other non-allergenic factors may trigger the specific IgE pathway and influence the occurrence of this disease (12). Over the last 20 years, accumulating evidence has shown that the interrelation between AS and subsequent development of asthma is more complex than a linear dose–response relationship, with gene–environment interactions and epigenetic modifications playing crucial pathophysiological roles (13). One impediment to understand the relationship between atopy and asthma is the common use of atopy as a binary variable (i.e., sensitized or non-sensitized). Another major impediment is that asthma is a heterogeneous condition, which comprises several different disease endotypes sharing similar symptoms. Recent data indicate that atopy may also encompass distinct endotypes characterized by different patterns of association with asthma (13). This opinion article outlines the most recent and debated findings about the interrelation between atopy and pediatric asthma.