Apparent but not real increase in asthma prevalence during the 1990s

Abstract

The authors investigated changes in asthma prevalence and perception of bronchoconstriction over 6 yrs in adults of Newcastle-upon-Tyne.Postal questionnaires were sent to 6,000 subjects aged 20-44 yrs in 1992-1993 and 1998-1999. Random samples of 600 responders had assessments of atopy, airway responsiveness, and their ability to perceive methacholine-induced bronchoconstriction. The prevalences of asthmatic symptoms, physician-diagnosis, and medication use increased by an average of 4.4%, particularly in subjects aged v30 yrs (8.7 versus 2.7). Atopy prevalence increased from 25% to 31% but atopics and nonatopics had similar mean changes in questionnaire data (5.2 versus 3.4). The probability of a positive methacholine test decreased as did the mean methacholine dose/response slope (0.00527 to 0.00379), indicating lower levels of airway responsiveness. This can be largely explained by an increase in use of inhaled corticosteroids (5.0-9.3%). The proportion of subjects perceiving bronchoconstriction during methacholine tests increased from 63 to 77%.The authors conclude that current changes in asthma epidemiology in adults may result from increased awareness of symptoms (and/or an increased willingness to report them), and from an increased willingness of physicians to make the diagnosis and prescribe treatment, not from increased disease prevalence. Eur Respir J 2002; 20: 826-833.

Changes in the prevalence of asthma in adults since 1966: the Busselton health study

“…Using varying definitions, studies have shown that, as we observed, the prevalence of DDA has increased more than have symptoms [31,32]. Other studies have not found significant changes in asthma prevalence in adults [33,34], although the latter study [34] was confined to adults aged .70 yrs.…”

Factors influencing the response to postal questionnaire surveys about respiratory symptoms

“…Estimates of the proportion of 'ghosts' among non-responders have varied considerably and were up to 25% in studies in North East England. 9,14,15 Were there to have been an actual rise in the prevalence of ghost patients, our results would in fact underestimate the decline in survey response rates. Sender recognition may be a further factor affecting response.…”

Overdiagnosis of asthma in obese and nonobese adults

“…29 In our study, more than 75% of the participants in whom asthma was eventually excluded reported dyspnea and wheezing in the 12 months before study entry. This increase in reporting of symptoms is probably occurring in concert with physicians' increased willingness to make a diagnosis of asthma in response to respiratory symptoms.…”