Interpreting longitudinal spirometry: Weight gain and other factors affecting the recognition of excessive FEV₁ decline

BACKGROUND: Excessive FEV(1) loss in an individual or a group can reflect hazardous exposures and development of lung disease. However, multiple factors may affect FEV(1) measurements. METHODS: Using medical screening data collected in 1884 chemical plant workers between 1973 and 2003, the influence of multiple factors on repeated measurements of FEV(1) was examined. RESULTS: The FEV(1) level was associated with age, height, race, sex, cigarette smoking, changes in body weight, and spirometer model. After controlling for these factors, longitudinal FEV(1) decline averaged 23.8 ml/year for white males; an additional loss of 8.3 ml was associated with one pack-year smoking and 5.4 ml with a one pound weight gain. Depending on the spirometer model, FEV(1) differed by up to 95 ml. CONCLUSIONS: The study results provide quantitative estimates of the effect of specific factors on FEV(1), and should be useful to health professionals in the evaluation of accelerated lung function declines.