Interestingly, chronic bronchitis was less predictive of 5-year lung function loss. This may have less to do with the pathophysiologic features of chronic airway disease due to cotton than to the variation in reporting chronic respiratory symptoms in this population.
There is evidence that cotton dust exposure leads to accelerated loss of lung function, though the magnitude of the effect and exposure-response relationships have not been well described.’’ The essential questions regarding chronic exposure and health remain: (1) Does cotton dust exposure lead to chronic loss of lung function? (2) Do the acute responses to cotton dust predict chronic loss of lung function? These results present no information with respect to question 1. Allergy medications more They do, however, provide evidence of an acute-chronic link. It is clear from cross-sectional studies that subjects with byssinosis symptoms have a higher prevalence of chronic bronchitis and lower levels of ventilatory function. It has remained unclear whether cotton textile workers with acute work-related symptoms and lung function drops actually have an accelerated loss of lung function. In contrast to cotton-exposed workers, those exposed to grain dust do exhibit such an acute-chronic link between across-shift drop in FEVi and chronic loss of FEVi.” In examining acute symptoms and across-shift changes prospectively, we need to examine the stability and reliability of these indicators. For example, symptom responses even on carefully standardized questionnaires are quite variable when asked about over time. Across-day spirometry may be influenced by tobacco smoking, age, initial level of FEVi, and diurnal variation.
Our results indicate that even with substantial survey-to-survey variability in responses, there is important information contained in both questionnaire responses and across-shift spirometry. Subjects with consistently negative or positive responses on the questionnaire sustained smaller or greater losses in baseline FEVi. Subjects with inconsistent symptom responses, regardless of direction of change, fell intermediately between the negative and positive acute responders. With regard to ventilatory function, subjects who had consistent across-shift drops in FEVi exceeding 5 percent had a 5-year loss in lung function greater than those with no response. In contrast to symptoms, inconsistent responders differed in the direction of their change, and this difference may reflect both regression to the mean and pathophysiology. The significantly greater 5-year loss in lung function observed in the group that responded at both surveys suggests that this group is at risk for chronic airflow obstruction. Further study is needed to clarify the quantitative relationship between cotton dust and endotoxin exposure and longterm respiratory effects.