This study evaluated the relationship between weight change and longitudina
l measurement of lung function among 361 men providing at least five pulmon
ary function tests. The men in this study were participants in a workplace
pulmonary surveillance program for subjects with exposure to refractory cer
amic fibers (RCFs) . Occupational and environmental studies are generally d
esigned to evaluate factors suspected of causing excess decline in lung fun
ction. Failure to adequately account for all significant factors may lead t
o erroneous conclusions regarding change in lung function. This study utili
zed two different statistical models to evaluate longitudinal changes in a
cohort of RCF workers. What was unique to this study was the modeling of lo
ngitudinally measured initial weight, weight change, and longitudinal expos
ure before and during the period of observation. Results showed a strong re
lationship between weight gain and longitudinal loss in lung function that
approximated forced vital capacity declines of 16 mL for every kilogram of
weight gain per year in both models. This value is comparable or greater in
magnitude and significance to other factors known to be inversely related
to lung function, such as age and pack-years smoking to time of initial tes
ting. In conclusion, weight gain was found to have a significant impact on
longitudinal change in lung function. Therefore, weight gain becomes a very
important variable that requires consideration whenever longitudinal studi
es of pulmonary function are conducted.