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To investigate the relationship between persistence and incidence rates of respiratory symptoms, and the cessation of cigarette smoking, the data from longitudinal studies conducted in Cracow, Poland and Tucson, USA were analysed jointly. Among 1722 subjects smoking at the beginning of the study, 468 had given up smoking at the 13-year follow-up. The persistence and incidence rates of chronic cough, chronic phlegm, wheeze and attacks of breathlessness were reduced by 50% in ex-smokers compared to the subjects continuing to smoke. The beneficial effects of smoking cessation were decreased in subjects smoking more cigarettes per day in the past and starting to smoke at a younger age. The symptoms were less likely if smoking ceased before the onset of any respiratory disease. These results were similar in the Cracow and Tucson populations, confirming the universal nature of the observations.

Data from four consecutive surveys of Tucson longitudinal study of airways obstructive disease were used to examine the relation of respiratory symptoms and pulmonary function to non-tobacco cigarette smoking. The surveys were conducted over a six-year period and provided data on 1802 subjects 15-60 years of age, with a total of 5659 individual questionnaires. Estimated odds ratio (OR) of current non-tobacco smoking for chronic cough was 1.73, for chronic phlegm: 1.53, and for wheeze: 2.01 (p less than 0.05). These estimates were adjusted for age, tobacco smoking and occurrence of the symptom in preceding survey. The increased risk of the symptoms was related to the habit continued for several years, and there was no immediate remission of the symptoms after quitting smoking. A significant (p less than 0.05) reduction in pulmonary function (FEV1, Vmax50 and their ratios with FVC) was found a year or more after current non-tobacco smoking was reported. Although the average consumption of non-tobacco cigarettes, believed to be marijuana smoking, was less than one per day, significant effects were still detectable in both pulmonary function and respiratory symptoms.

Data from the French PAARC (Pollution Atmosphérique et Affections Respiratoires Chroniques) study were used to assess the effect of a priori moderate occupational exposure to dust, gases or chemical fumes on the prevalence of respiratory symptoms and ventilatory function. In this community-based population, without households 'headed' by manual workers, 34% of the 8692 men and 23% of the 7772 women, 25-59 years of age, ever occupationally active, reported some exposure. The studied relationships were adjusted for age, height, smoking habits, socio-occupational class, education and air pollution by logistic or linear regression methods. For men and women, some 50% increase (p less than 0.01) in chronic cough, chronic bronchitis, dyspnoea grade 2 and wheezing prevalence was observed in the exposed group compared to the never exposed, with the strongest association for wheezing. FEV1 and FEF25-75% were not associated with occupational exposure. Among men, FEV1/FVC and FEF25-75%/FVC were significantly lower (p less than 0.001 and p less than 0.05) among the exposed compared to never exposed, but FVC was significantly greater (p less than 0.05). Among women, occupational exposure was significantly related to a lower FEV1/FVC in the subgroup with a history of asthma or wheezing. Results suggest that occupational exposures of relatively low intensity, encountered in the non-industrial work places may constitute a non-negligible risk for respiratory health.

The relation of mortality to ventilatory function and some respiratory symptoms detected during interview has been studied in 3047 men and women followed-up for 13 years. The analysis was performed for all natural causes of death, and separately for deaths due to circulatory diseases and neoplasms. The results confirm the strong predictive power of ventilatory impairment for overall and circulatory mortality, even after adjustment for age, cigarette smoking and other factors in logistic regression models. The risk of cancer death in men increased with decrease of FEV1. However, chronic cough, mucus hypersecretion or asthmatic syndrome were not related to subsequent mortality. A strong predictor of overall and circulatory 'mortality' in men was also self-assessed health status. This was independent of other factors.