Year: 2012
Type: dissertation
Study design: Observational Study
Abstract: The aim of the study was to assess the prevalence of bronchial hyperresponsiveness (BHR) in the Finnish adult general population, its determinants and risk factors. Histamine and methacholine challenges were compared to assess their agreement. The association of active and passive smoking with BHR severity was studied in detail. Incident adult asthma in Helsinki over the 11 years follow up was investigated. For the BHR comparison study 79 subjects were included in Kemi, Finland, whereas 292 randomly selected subjects (26-66 years) were included for the Helsinki BHR-study. The follow up study of incident asthma and respiratory symptoms in 2007 included 4302 of those, who had originally (n=6062) taken part in the FinEsS-Helsinki postal survey in 1996. In Kemi, bronchial challenges to methacholine and histamine were performed to each subject in a randomized order. In Helsinki, following the interview, skin prick tests, spirometry, and fractional exhaled nitric oxide (FENO) measurement, the BHR test with histamine was assessed. Provocative doses (PD15FEV1 and PD20FEV1) for histamine and methacholine were assessed. The highest cumulative dose for methacholine was 2.6 mg, and the highest non-cumulative dose for histamine was 1.6 mg. Histamine PD15FEV1 ≤0.4 mg (BHRms) and ≤1.6 mg (BHR) served a cut-off points in the logistic regression analysis. BHR tests with metacholine and histamine tests showed a good agreement in classifying severity of BHR in a population with no previous diagnosis of asthma or chronic bronchitis (weighted kappa 0.64; CI 95% 0.46-0.82). In the general adult population in Helsinki, the prevalance of BHR was 21%, and for BHRms 6% . The main determinants for BHR were a decreased FEV1 and airway obstruction, which yielded over four-fold risk for BHR. Smoking and BHR were dose-dependently associated, and the young age of starting to smoke and exposure to environmental tobacco smoke (ETS), constituted on BHR. Respiratory symptoms, asthma or wheezing in the early childhood (<5) and female gender were associated with BHR, as did MEF50 < 63% predicted. Body mass index (BMI) did not associate with BHR. The association between FENO and BHR was dependent on smoking habits. In the 11 years follow up, the asthma incidence rate was 3.7/1000/ year. Remission was 17% during that period. Incidence rate of allergic rhinoconjunctivitis (ARC) was 16.8/1000/year. Living on countryside or in a farm during the first 5 years of life decreased the risk for incident ARC. ARC doubled the risk for incident asthma. In a longitudinal setting, our results suggested that asthma incidence in Finland has leveled on a plateau. Findings of this thesis suggest that quantitative assessment of BHR by different cut off levels provides a tool for characterization of phenotypes of airway disorders in epidemiological studies.
Source: Työväentutkimus Vuosikirja
Author: Maria Juusela
Language: English
Subfield: Pulmonary and Respiratory Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W1589549031