Lifetime asthma incidence is related to age at onset and allergies in western Sweden.

Although asthma is more frequently diagnosed in childhood, a substantial proportion of cases manifests in adulthood. Nonetheless, few studies have comprehensively examined asthma incidence across different ages, genders, and asthma phenotypes. We conducted a retrospective evaluation of asthma incidence from birth to late adulthood, stratified by age, gender, and the presence or absence of allergies. Our analysis indicates that a significant number of asthma cases emerged in adulthood, particularly among middle-aged women, with adult-onset asthma surpassing childhood-onset asthma after the age of 35 years. Additionally, allergic asthma was more common in younger than older individuals but decreases with age, ultimately leading to a higher proportion of non-allergic asthma in older than younger individuals. These findings underscore the predominance of adult-onset asthma among females and confirm the majority of allergic asthma in children, which declines with age. Additionally, increasing age is associated with increased incidence of non-allergic asthma. Asthma heterogeneity should be considered in both clinical management and research.