The relationship between age and bronchial responsiveness - Evidence from a population survey

Objectives: Increased bronchial responsiveness is a feature of symptomatic asthma, and it predicts the onset of wheezing. We have investigated the rel ationship between bronchial responsiveness and age in a population sample w ith an age range of 45 to 86 years. Design: Cross-sectional population survey. Setting: Population of Central Manchester, UK. Participants: An age-stratified random sample of white adults aged greater than or equal to 45 years old and living in Central Manchester, They were r ecruited from their primary care physician (general practitioner) lists. Pa tients with confusion and patients who were housebound were excluded. Measurements: Respondents to a mail questionnaire were invited to attend a methacholine bronchial challenge performed using the Newcastle dosimeter me thod. Respondents with ischemic heart disease or respondents taking oral st eroids, beta-blockers, or anticholinergic medication were excluded. Results: Of the 783 subjects contacted, 92.3% of the subjects responded, an d 508 subjects returned enough information for us to deduce their suitabili ty for the bronchial challenge, Of the 395 suitable subjects, 247 subjects participated (62.5% of those invited: 31.5% of the study population), and 2 08 participants completed the bronchial challenge. Participants were slight ly younger than nonparticipants, but they were otherwise representative of the population, Increased bronchial responsiveness (provocative dose of met hacholine causing a 20% fall in FEV1 less than or equal to 200 mu g) was pr esent in 71 (34.1%) participants. Stepwise multiple regression analysis sho wed weak, independent, positive associations between bronchial responsivene ss and age, and between bronchial responsiveness and the total immunoglobul in E level. There was an independent negative relationship between bronchia l responsiveness and the airways caliber (expressed as standardized residua ls; R-2 = 0.29). Conclusions: We have found a high prevalence of increased bronchial respons iveness in this inner-city population of older adults. Bronchial responsive ness shelved a weak independent positive association with age.