Tobacco use among designated air pollution victims and its association with lung function and respiratory symptoms: a retrospective cross-sectional study

OBJECTIVES We sought to elucidate the long-term association of tobacco use and respiratory health in designated pollution victims with and without obstructive pulmonary defects. DESIGN A retrospective cross-sectional study. SETTING The register of pollution victims in Kurashiki, Japan. PARTICIPANTS 730 individuals over 65 years of age previously diagnosed with pollution-related respiratory disease. Patients were classified into four groups according to their smoking status and whether they had obstructive pulmonary disease. We then compared the prevalence of respiratory symptoms and lung function over time between groups. PRIMARY OUTCOME MEASURES Spirometry was performed and a respiratory health questionnaire completed in the same season each year for up to 30 years. RESULTS Rates of smoking and respiratory disease were high in our sample. Although respiratory function in non-smoking patients did not completely recover, the annual rate of change in lung function was within the normal range (p<0.01). However, smokers had worse lung function and were more likely to report more severe pulmonary symptoms (p<0.01). CONCLUSIONS Patients' respiratory function did not fully recover despite improved air quality. Our results suggest that, in the context of exposure to air pollution, tobacco use causes additional loss of lung function and exacerbates respiratory symptoms.