Rhinitis increase the risk for adult-onset asthma--a Swedish population-based case-control study (MAP-study).

The aim of the study was to examine certain predictors, especially non-infectious rhinitis, and the risk for adult-onset asthma. A nested case-control study of adult-onset asthma was performed in a random sample from the general population (n = 15,813), aged 21 to 51 years. Cases for the study included subjects reporting physician-diagnosed asthma (n = 235) and controls (n = 2044) were randomly selected from the whole population sample. The case-control sample was investigated with a comprehensive respiratory questionnaire. Odds ratios were calculated stratified for sex, year of diagnosis and birth-year. Adult-onset physician-diagnosed asthma was associated with occurrence of non-infectious rhinitis before asthma onset (OR = 5.4, 95% CI 4.0-7.2), especially among smoking non-atopics (OR = 9.1, 95% CI 5.3-15.4). Smoking before asthma onset increased the risk for asthma (OR = 1.5, 95% CI 1.1-2.1). In conclusion, this population-based case-control study indicate that non-infectious rhinitis and current smoking, especially among non-atopics, are associated with increased risk for adult-onset asthma.