A recently published multinational cohort study may be the largest to date that’s found the age of asthma onset is an integral factor in defining the severity of disease and the frequency of comorbidities.
“It’s very simple to ask your patient: ‘Did you have asthma as a child? When did your asthma start?’ ” coauthor Guy Brusselle, MD, a professor at the University of Ghent (Belgium), said in an interview. “You do not need expensive investigations, CT scans or proteomics or genomics; just two simple questions.”
The retrospective cohort study, published in the Journal of Allergy and Clinical Immunology: In Practice, combined national electronic health records databases from five different countries – the United Kingdom, Spain, Italy, the Netherlands, and Denmark – that included 586,436 adult asthma patients. The study divided the patients into three subtypes: childhood-onset asthma, meaning a diagnosis before age 18 (n = 81,691); adult-onset disease, defined as a diagnosis between ages 18 and 40 (n = 218,184); and late onset, defined as a diagnosis made after age 40 (n = 286,561).
Dr. Brusselle said the study found stark differences in characteristics between the three subtypes, including an increasing risk for women with later age of onset. Across the five databases, females comprised approximately 45% of those with childhood-onset asthma, but about 60% of those with later-onset disease, Dr. Brusselle said.
As for characteristics of asthma, 7.2% of the cohort (n = 42,611) had severe asthma, but the proportion was highest in late-onset asthma, 10% versus 5% in adult onset and 3% in childhood onset. The percentage of uncontrolled asthma followed a similar trend: 8%, 6%, and 0.4% in the respective treatment groups.
The most common comorbidities were atopic disorders (31%) and overweight/obesity (50%). The prevalence of atopic disorders was highest in the childhood-onset group, 45% versus 35%, and 25% in the adult-onset and late-onset patients. However, the trend for overweight/obesity was reversed: 30%, 43%, and 61%, respectively.
“The larger differences were when late-onset asthma was compared to adult-onset asthma with respect to comorbidities,” Dr. Brusselle said. “The late-onset asthma patients more frequently had nasal polyposis.” These patients typically lose their sense of smell, as in COVID-19. However, in nasal polyposis the loss is chronic rather than transient.
Pulmonologists should be attuned to the prevalence of overweight/obesity in the late-onset group, Dr. Brusselle said. “We know that obesity is an important risk factor for diabetes, and then obesity is also associated with gastroesophageal reflux – and we know that gastroesophageal reflux is a risk factor for asthma exacerbations.”
Smaller studies have arrived at the same conclusions regarding the relationships between asthma severity and age of onset, Dr. Brusselle said. What’s notable about this study is its size and the consistency of findings across different national databases.
“In childhood onset you need to watch for different allergies – atopic dermatitis and allergic rhinitis – but in late-onset asthma look for obesity, diabetes and reflux disease, and nasal polyposis,” he said.
Sally E. Wenzel, MD, professor at the University of Pittsburgh and director of the Asthma and Environmental Lung Health Institute at the University of Pittsburgh Medical Center, concurred that the size of this study makes it noteworthy.
“It’s certainly far and away the largest study of its kind that’s ever been done, and it’s multinational,” she said in an interview. “Just doing a study like this with thousands and thousands of patients is a step in the right direction. That’s probably what’s very unique about it, to bring all of these clinical cohorts as it were together and to look at what is the relationship of the age of onset.”
She also said the study is unique in how it delineates the groups by age of onset.
“In addition to this concept that there’s a difference in asthma by the age that you got diagnosed with it, I think it’s also important to just remember that when any physician, be they a specialist or nonspecialist, sees a patient with asthma, they should ask them when did their symptoms develop,” she said. “These are really simple questions that don’t take any sophisticated training and don’t take any sophisticated instruments to measure, but they can be really helpful.”
GlaxoSmithKline supplied a grant for the study. Dr. Brusselle disclosed relationships with AstraZeneca, Boehringer Ingelheim, Chiesi, GSK, Novartis, Sanofi, and Teva. A study coauthor is an employee of GSK. Dr. Wenzel reported no disclosures.
A version of this article first appeared on Medscape.com.