Rationale: Acute airway response, measured as cross-shift change in FEV(1), to cotton dust may lead to subsequent chronic loss of lung function in exposed workers.
Objectives: To explore the association between the magnitude and frequency of cross-shift change and chronic loss of FEV(1).
Methods: Four hundred eight cotton workers and 417 silk workers from Shanghai textile mills were observed prospectively for 20 years, with cross-shift measurements at baseline and follow-up surveys at approximate 5-year intervals. To account for repeated measures of 5-year change, generalized estimating equations were used to estimate the relationship between the magnitude of cross-shift change in FEV(1) (DeltaFEV(1)) and subsequent 5-year annualized change. Linear regression models were used to examine the association between the number of drops in cross-shift FEV(1) (DeltaFEV(1) < 0) and annualized change over the entire study period.
Measurements and main results: Exposure to cotton dust was associated with a 10 ml/year decrement in 5-year annualized FEV(1) decline. In addition, every 10 ml in DeltaFEV(1) drop was associated with an additional 1.5 ml/year loss in annualized FEV(1) decline. The association between the frequency of drops and annualized decline was stronger for cotton workers than for silk workers over the entire study period.
Conclusions: Cotton workers had larger and more frequent drops, as well as excessive chronic declines in FEV(1), than did silk workers. The magnitude and frequency of cross-shift drops were associated with chronic loss in FEV(1) over the entire 20-year period examined.