["Physiologic" aging in 5 years of pulmonary function in 140 iron miners].

Ageing of the lung function in 5 years was studied in a group of 140 iron-ore miners, aged initially from 36 to 55 years. These men had no respiratory symptom and no pulmonary radiological abnormality. The sample was stratified on age and smoking. These factors were studied by a two-way analysis of variance. Lung function testing was performed twice, at 5 years of interval, in the same conditions. It consisted in: spirometry (for measuring FVC, FEV1, FEV1/FVC); a bronchial challenge test with acetylcholine (measurement of the fall of FEV1 after the test); measurement of total lung capacity (TLC) and residual volume (RV) by the open-circuit helium dilution method, and measurement of the transfer factor of the lung for CO, by the steady-state method (TCO/V). The only indices, whose values significantly changed in 5 years were: FVC, FEV1 and TCO/V. Their decrease rate did not appear to be significantly linked to age nor to smoking. According to these results, it seems that the decline of the pulmonary function is relatively constant during the middle period of life and that it is not strongly influenced by smoking, but only among subjects who remain without any respiratory symptom.