**Background:** Chronic airway diseases, including asthma and COPD, are major global health burdens. COPD is the third leading cause of death worldwide, and asthma, though less fatal, can cause significant morbidity. Emerging evidence suggests that adult chronic airway disease may originate in early life, with childhood asthma being a potential risk factor for COPD. However, the long-term prognosis of severe childhood asthma remains poorly understood. This study aims to investigate the association between severe childhood asthma and chronic airway disease in adulthood using the Kongsberg cohort, a unique group of approximately 5000 children with severe asthma who stayed at a care facility in Kongsberg, Norway, between 1950 and 1979.
**Methods:** This is a prospective cohort study with an average follow-up of 60 years. The study population consists of children with severe asthma referred to the Kongsberg facility, primarily from Denmark. Data from index cards and registration lists will be linked to each individual's unique civil personal registration (CPR) number via the Danish Health Data Authority. Eligible individuals currently alive and residing in Denmark will be invited for a comprehensive follow-up examination at the Respiratory Research Unit at Copenhagen University Hospital Hvidovre. The examination includes questionnaires (ACT, ACQ-7, CAT, CCQ, MRC dyspnea scale), blood samples (CRP, alpha1-antitrypsin, white cell count, hemoglobin, vitamin D, total IgE, and genetic analysis), fractional exhaled nitric oxide (FeNO), skin prick test for 9 aeroallergens, spirometry (FEV1, FVC), bronchodilator reversibility test, body plethysmography (VC, RV, TLC), diffusion capacity (DLCO), and mannitol bronchial challenge test. A genome-wide scan will be performed to investigate SNPs related to asthma or COPD. Additionally, nationwide registry data from the Danish National Patient Registry (since 1977), Danish National Prescription Registry (since 1995), income/occupation/education registries (since 1980), and the Danish Registry of Causes of Death (since 1970) will be analyzed. The primary endpoint is the prevalence of childhood asthma remission (defined as no asthma medications and no symptoms in the past 12 months). Secondary endpoints include prevalence of airflow limitation, socioeconomic status, mortality, and genetic susceptibility. Sample size calculation, based on a previous study showing 10% remission in severe childhood asthma, indicated that at least 139 subjects are needed for 5% absolute error and 5% type I error. Statistical analyses will use t-tests, chi-square tests, logistic regression (odds ratios), Cox regression (hazard ratios), and genetic analyses.
**Key Results:** As this is a study protocol, no results are presented. The paper describes the planned analyses and expected outcomes. The primary outcome will be the proportion of participants with asthma remission. Secondary outcomes will quantify airflow limitation, socioeconomic differences compared to age-matched controls, mortality rates, and genetic associations.
**Clinical Implications:** This study will provide critical long-term data on the natural history of severe childhood asthma, including remission rates, development of airflow limitation, and mortality. By identifying early-life risk factors and genetic susceptibilities, the findings may inform prevention strategies and clinical management to reduce the burden of chronic airway diseases. The comprehensive examination and registry linkage offer a unique opportunity to understand disease trajectories from childhood to late adulthood, potentially guiding early interventions to improve respiratory health outcomes.