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The relationship between age and bronchial responsiveness: evidence from a population survey
1University Department of Medicine for the Elderly, Barnes Hospital, Manchester, UK.
Objectives:
Increased bronchial responsiveness is a feature of symptomatic asthma, and it predicts the onset of wheezing. We have investigated the relationship between bronchial responsiveness and age in a population sample with 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 > or = 45 years old and living in Central Manchester. They were recruited from their primary care physician (general practitioner) lists. Patients 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 method. Respondents with ischemic heart disease or respondents taking oral steroids, beta-blockers, or anticholinergic medication were excluded.
Results:
Of the 783 subjects contacted, 92.3% of the subjects responded, and 508 subjects returned enough information for us to deduce their suitability for the bronchial challenge. Of the 395 suitable subjects, 247 subjects participated (62.5% of those invited; 31.5% of the study population), and 208 participants completed the bronchial challenge. Participants were slightly younger than nonparticipants, but they were otherwise representative of the population. Increased bronchial responsiveness (provocative dose of methacholine causing a 20% fall in FEV1 < or = 200 microg) was present in 71 (34.1%) participants. Stepwise multiple regression analysis showed weak, independent, positive associations between bronchial responsiveness and age, and between bronchial responsiveness and the total immunoglobulin E level. There was an independent negative relationship between bronchial responsiveness and the airways caliber (expressed as standardized residuals; R2 = 0.29).
Conclusions:
We have found a high prevalence of increased bronchial responsiveness in this inner-city population of older adults. Bronchial responsiveness showed a weak independent positive association with age.