Rise and Fall of the FEV1

Most studies of the rate of decline inventilatory capacity in normal subjects take into account a relativelyrestricted number of factors, such as age, smoking, and dust exposure. There is increasing evidence to suggest that such a limited approach isinadequate. To carry out a prospectivestudy of those factors influencing the rate of decline of theventilatory capacity in a cohort of automobile workers. Prospective cohort study. Southern Ontario, Canada. A cohort of181 workers employed in assembling and spray painting the chassis ofnew cars, a minority of whom used paints containing isocyanates. All participants underwent annualanthropometric measurements. Spirometry was carried out at yearlyintervals, and a questionnaire relating to respiratory symptoms andsmoking habits was completed annually by all participants. Dailymonitoring of the isocyanate levels was carried out. There was no indication of any effect fromisocyanate exposure. The annual decline in the FEV1 wassimilar to that found in other studies, with the respective annualdecrements for smokers, ex-smokers, and nonsmokers being 0.055 L, 0.046L, and 0.035 L, respectively. The decline of the FEV1 inthose > 35 years old and < 35 years old differed appreciably. Thedecrements in the FEV1 in subjects < 35 years old wereinfluenced as much by excessive weight gain as by cigarette smoking. Loss of weight in those significantly overweight was frequentlyassociated with improved lung function. While age and smoking play an important role in determining the rate ofdecline in the ventilatory capacity, it is clear that body weight playsa significant role and needs to be taken into account in allepidemiologic studies of the ventilatory capacity.