Abstract
Aim To estimate the incidence rate of asthma from age 8 to 28 years and evaluate early-life risk factors for asthma onset at different ages.
Methods In 1996, within the Obstructive Lung disease In Northern Sweden studies, a cohort of 3430 schoolchildren (97% of invited) was recruited at age 8 years to a prospective study about asthma. The cohort was followed annually from 8–19 years and at 28 years by questionnaire surveys (67% of the original cohort participated). Asthma was categorised as never asthma, onset ≤8 years, 9–13 years, 14–19 years, or >19 years.
Results Of 3430 individuals in the cohort, 690 (20.1%) reported asthma in any survey. The average incidence was 10.0/1000 per year ≤8 years, 11.9/1000/year from 9 to 13 years, 13.3/1000/year from 14 to 19 years, and 6.1/1000/year >19 years. The incidence was higher among boys until age 10y, but from age 15y, it became higher among girls. Family history of asthma, allergic sensitisation, and breastfeeding <3 months were associated with asthma onset throughout the study. Low birthweight, maternal smoking during pregnancy, severe respiratory infection, rhinoconjunctivitis and eczema were associated with asthma onset ≤8 years and 9 to 13 years.
Conclusions The incidence of asthma was high during childhood and the teenage period and decreased substantially during young adulthood. Early life factors were associated with asthma onset throughout childhood but had also a lasting effect on asthma incidence until adulthood.
Footnotes
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Conflict of interest: Helena Backman has received payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events from Astra Zeneca and Boehringer Ingelheim, outside the submitted work.
Conflict of interest: The remaining authors have nothing to disclose.
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- Received February 8, 2022.
- Accepted June 16, 2022.
- Copyright ©The authors 2022.
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