Asthma phenotypes based on health services use for allergic diseases in a province-wide birth cohort

Background: Many previous studies on asthma phenotypes were conducted in selected clinical populations and overlooked changes throughout the life course.

Objective: To identify asthma phenotypes based on use of health services for allergic diseases in 3 life periods and document transitions among phenotypes across life periods.

Methods: In a population-based cohort of 78,211 individuals born in 1974 in the province of Québec, Canada, we documented medical visits and hospitalizations for asthma and other allergic diseases until 1994. Phenotypes based on clusters of health services use in childhood (8-12 years of age), adolescence (13-17 years of age), and young adulthood (18-20 years of age) were identified using a hierarchical method among 9,989 individuals (12.8%) who had at least one health encounter for asthma during follow-up. Population-level probabilities of transitioning among phenotypes were estimated in the full study population.

Results: In the subset with asthma, 6 phenotypes were identified during both childhood and young adulthood and 7 during adolescence. The most common phenotype was no asthma or allergic diseases: 58% in childhood, 42% in adolescence, and 54% in adulthood. The second most common was the mild asthma and no allergic diseases phenotype, representing 36%, 31%, and 21%, respectively, in these 3 periods. In the study population, 87% of the individuals remained in the no asthma phenotype group during the follow-up. Most individuals in the asthma phenotypes transitioned over time.

Conclusion: Our study uniquely contributes to a better understanding, at the population level, of the manifestations and transitions in asthma phenotypes during the life course.