Relations between occupation, smoking, lung function, and incidence and mortality of chronic non-specific lung disease: the Zutphen Study.

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Abstract
Information gathered in the "Zutphen study", the Dutch contribution to the Seven Countries Study was used for the present study. Follow up data from 1965 to 1 July 1985 were used. During this follow up, the morbidity state of the participants was verified at regular intervals. In 1965 lung function was measured by spirometry and the vital capacity (VC) and forced expiratory volume in one second (FEV1) were available. A complete set of data was available for 668 men. The occurrence of chronic non-specific lung disease (CNSLD) at a specific time was coded by one physician, using strict criteria. Information about the cause of death was obtained and coded by one physician in 1985. Occupation was coded and a distinction between blue and white collar workers was made. For the analysis of the relation between age, lung function, smoking habits, and occupational state with CNSLD incidence and mortality, proportional hazard models were used. Blue collar workers had a significantly raised risk for incidence of CNSLD only. The hazard ratio for blue v white collar workers with CNSLD mortality was 1.4 but not statistically significant. It was concluded that occupation is clearly related to incidence of CNSLD. There were indications that occupation is related to mortality from CNSLD. A reduced FEV1 was a strong predictor of both CNSLD incidence and mortality. It is noteworthy that small differences in age and height standardised lung function were significantly related to incidence of CNSLD, mortality from CNSLD, and total mortality. Although these differences in lung function have no direct clinical importance for the individual subject, they indicate a raised morbidity and mortality risk for the population.