At baseline visit the diagnostic studies performed were: spirometry, PEF (peak expiratory flow) follow-up, other respiratory physiology measurements, laboratory, skin-prick, AQ20 (Airways questionnaire 20), 15D, background data. At follow-up visit, asthma status, co-morbidities (chronic rhinitis or obstructed nose, allergic rhinitis or conjunctivitis, diabetes, hypertension, coronary heart disease, COPD (chronic obstructive pulmonary disease) and any other patient-reported disease), medication (including medication to other diseases and the disease treated), control, severity and lung function were evaluated. In addition to the data gathered at these visits, data on asthma follow-up visits, exacerbations, hospitalisations, possible occupationally induced asthma and prescribed asthma medication were collected from hospital clinics, primary health care, occupational health care and private practices for the whole 12-year follow-up period. In addition, the use of medication that was realised, i.e., medication bought from pharmacy, will be retrieved. In addition to asthma-specific factors, data include occupational, lifestyle and socioeconomic factors at the follow-up visit.