ASTHMA, AIRWAYS RESPONSIVENESS AND AIR-POLLUTION IN 2 CONTRASTING DISTRICTS OF NORTHERN ENGLAND

Background - To assess the possible magnitude of differences between n ormal populations an epidemiological investigation of asthma was condu cted in two strongly contrasting districts of northern England - rural West Cumbria on the west coast and urban Newcastle upon Tyne on the e ast coast. Methods - A cross sectional survey of randomly identified m en aged 20-44 years was conducted in two phases: phase 1, a postal sur vey of respiratory symptoms and asthma medication in 3000 men from eac h district; and phase 2, a clinical assessment of 300 men from each di strict comprising investigator administered questionnaires, skin prick tests, spirometry, and methacholine challenge tests. Results - The ph ase 1 (but not phase 2) study showed a small excess of ''ever wheezed' ') in Newcastle (44% versus 40%), but neither phase showed differences between the two districts for recent wheeze or for other symptoms cha racteristic of asthma. There were also no differences with regard to d iagnosed asthma, current asthma medication, spirometric parameters, or airways responsiveness. The prevalence of quantifiable airways respon siveness (PD20 less than or equal to 6400 mu g) was 27.7% in West Cumb ria and 28.2% in Newcastle. Regression analyses showed that PD20 was n egatively associated with atopy and positively with forced expiratory volume in one second (FEV(1)); that an association between PD20 and cu rrent smoking could be explained by diminished FEV(1); and that PD20 w as not related to geographical site of residence. Conclusions Neither airways responsiveness nor the other parameters of diagnostic relevanc e to asthma varied much between the two study populations, despite the apparent environmental differences. The most obvious of these were th e levels of outdoor air pollution attributable to vehicle exhaust emis sions, the ambient levels of which were 2-10 fold greater in Newcastle . Our findings consequently shed some doubt over the role of such poll ution in perceived recent increases in asthma prevalence. It is possib le, however, that an air pollution effect in Newcastle has been balanc ed by asthmagenic effects of other agents in West Cumbria.