Summary: The ventilatory capacity, including flowvolume curves of 313 men, all 50 years old, was examined in 1963 and 1967. The group as a whole, which included persons with chronic bronchitis, with ".other respiratory symptoms," and without respiratory symptoms, showed the same absolute decrease in ventilatory capacity.Vital capacity, forced expiratory volume, and maximum expiratory flow all dropped more for the smokers than for either the non-smokers or the ex-smokers. In those who had stopped smoking for four years or less, however, ventilatory capacity did not decline significantly less than in those who continued to smoke. Tables V and VI for references). Factors such as the nature of the ambient air and smoking habits also affect the ventilatory capacity. A better way of studying the influence of different factors is to follow pulmonary function from year to year in the same people (Higgins and Oldham, 1962 ;Fletcher, 1968 ;Higgins et al., 1968).
IntroductionThe present investigation had three aims: (1) to record the changes in the ventilatory capacity during a four-year period in a randomly selected sample of men born in the same year; (2) to determine whether there was any difference in the ventilatory capacity between groups which differed as regards respiratory symptoms and smoking habits; and (3) to analyse the drop with age in comparison with a prediction from regression equations.The results of a cross-sectional study in 1963, using the same sample of men, on the connexion between smoking and ventilatory capacity have been published, as have the results from a control group without any respiratory symptoms (Wilhelmsen and Tibblin, 1966;Wilhelmsen, 1968).
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