The prevalence of asthma and heart disease in transport workers: a practice-based study.

BACKGROUND: There has been widespread concern that the increasing incidence of asthma observed during the late 1980s might have arisen because of environmental pollution, and in particular vehicle pollution. The General Practice Morbidity Survey in 1991/92 (MSGP4) collected data on occupation, employment status, and smoking habit linked individually to each patient record.
OBJECTIVES: To examine whether people with occupations that have high exposure to vehicle exhaust fumes have an increased prevalence of asthma, acute respiratory infections, and ischaemic heart disease (IHD).
METHOD: Men aged 16 to 64 years were grouped by Standard Occupational Classification codes; 93,692 employed and 20,858 not-employed men were studied separately. Those with likely high occupational exposure were grouped together ('all-exposed')--the remainder occupations in corresponding chapters of the code were used as controls. We compared 12-month age and smoking standardised disease prevalence ratios for asthma, chronic obstructive pulmonary disease (COPD), acute respiratory infections (IHD), and all circulatory disorders in the all exposed and individual exposed occupations with their matching controls. Also the mean frequency of consultations per person consulting was calculated for each occupational group and disease.
RESULTS: For employed persons, the prevalence ratio (PR) for asthma in the all-exposed, (116, 95% confidence interval [95% CI] = 101-130) exceeded that for all employed persons (100); however, the difference compared with chapter-matched controls (PR = 97, 95% CI = 92-103), was not statistically significant. Results for COPD were similar. Prevalence ratios in motor mechanics, a high-exposure group, were 98 (95% CI = 70-127) 96 (95% CI = 70-123) for asthma and COPD respectively. Among the employed, prevalence ratios for IHD in all but one of the individual occupation groups examined did not differ from the average, however among those not employed the ratio in the all-exposed (PR = 152, 95% CI = 128-174) exceeded that in the controls (PR = 112, 95% CI = 104-120).
CONCLUSION: Occupational groups exposed to motor vehicle pollution have a marginally increased prevalence of asthma compared with working males generally, though not compared with occupation matched controls. This study has demonstrated a methodology for using GP data to examine occupation-related disease. This could be used in future by augmenting GP data with occupation and smoking information.