While the occurrence of concomitant asthma and atopic dermatitis (AD) in patients is well known, the impact of the causal relationship between asthma and AD is not fully understood. Furthermore, data on the impact of asthma in children with AD regarding healthcare utilization remain absent. Therefore, an awareness of the healthcare utilization and drug use in this subgroup is imperative to help improve prevention strategies and treatment options by targeting clinically meaningful subgroups of asthma.

For a paper published in Dermatitis, my colleagues and I aimed to determine the incidence of asthma in children with AD compared with the background population (children without AD) and to examine the healthcare utilization and drug use for asthma in children with concomitant AD and asthma compared with those with asthma alone.

A Nearly Four-Fold Risk of Asthma

In a nationwide, register-based, cohort study, we identified all children born in Denmark from 1997-2018. The study included 18,625 children with AD and 74,500 matched children from the background population. The mean age at baseline was younger among children with mild (2.3) and moderate AD (2.4) compared with the background population (3.2). The registries used contain prospectively collected data, including diagnoses and treatment procedures from all hospital admissions and outpatient contacts at all hospitals, as well as from several private clinics. We followed the children from AD diagnosis until study end point, their 18th birthday, migration, or death from any cause, whichever came first. Children with AD were age- and sex-matched with background population individuals, and in this group, all children with an asthma-only diagnosis were identified.

 We found that children with AD had a nearly four-fold increased risk of asthma compared with age- and sex-matched children without AD. Furthermore, the risk of asthma increased with increasing AD severity, with incidence rates per 1,000 person-years of asthma of 20 children in the mild AD group and 37 in the very severe AD group (Table).

More Hospital Admissions, ED Visits

During the study period, 4,203 and 5,298 cases of definite asthma were observed among children with AD and the age- and sex-matched controls from the background population, respectively. A total of 2,196 cases of possible asthma occurred among children with AD, compared with 2,490 in the controls. Additionally, during the first year following an asthma diagnosis, children with concomitant AD and asthma had a significantly higher risk of asthma-related hospital admissions (HR, 2.58; 95% CI, 2.03-3.29), emergency department visits (HR, 1.88; 95% CI, 1.44-2.43), outpatient clinic visits for asthma (HR, 1.98; 95% CI, 1.76-2.22), filled prescriptions of asthma medication (HR, 1.33; 95% CI, 1.30-1.37), and rescue course corticosteroids (HR, 1.92; 95% CI, 1.29-2.87) compared with children with asthma only. The associations remained significant even when adjusted for socioeconomic status, maternal education level at baseline, number of siblings, age, and sex.

Our findings suggest that dermatologists should be aware of asthma symptoms and family history in children with AD so that early diagnosis can be initiated. Early identification of asthma is crucial in children with AD to prevent exacerbations and deterioration of lung function. In addition, proactive prevention and education strategies targeting this subgroup may help to avoid hospitalizations and emergency department visits, and thus reduce healthcare costs. My colleagues and I would like to see future studies that further explore this causal association between asthma and AD to determine whether this is a marker of more difficult-to-treat asthma in children with AD and to help identify areas for focused interventions.