Risk factors and respiratory symptoms of incident asthma
In an adjusted Poisson regression analysis, allergic rhino-conjunctivitis was a significant risk factor for incident physician-diagnosed asthma, defined by model A, in both observation periods, with RR 2.62 (1.69-4.07) and RR 2.39 (1.48-3.87), respectively (Table 4). Female sex was a significant risk factor in the observation period 2006 to 2016, RR 1.99 (1.22-3.25) but not from 1996 to 2006. Family history of asthma was a borderline risk factor for the period 1996 to 2006, RR 1.50 (0.93-2.43), but significant from 2006 to 2016, RR 1.75 (1.05-2.90). Ex-smoking was a borderline risk factor from 1996 to 2006.
The same analysis as above yielded a closely similar pattern also according to model B with family history of asthma, allergic rhino-conjunctivitis, female sex and ex-smoking as significant risk factors for incident physician-diagnosed asthma during the period 1996 to 2006. The same risk factors, except ex-smoking, were found for the period 2006 to 2016 (Supplemental Table 1).
Among individuals with incident physician-diagnosed asthma in the cohort observed from 1996 to 2006, 70% reported attacks of SOB last 12 months, 43% allergic rhino-conjunctivitis and 83% used asthma medication at the follow up in 2006. The corresponding figures for individuals with incident physician-diagnosed asthma in the cohort observed from 2006 to 2016 were 65%, 44% and 80%, respectively. None of these variables differed significantly at follow-up between incident asthma cases in the two cohorts.