Longitudinal predictors of bronchial hyperresponsiveness and FEV₁ decline in bakers

To determine long-term predictors of bronchial hyperresponsiveness (BHR) and forced expiratory volume in one second (FEV₁) decline.

A longitudinal study in 110 bakers in 4 industrial bakeries and 38 non-exposed workers was conducted at the workplace with a mean of 3.3 visits per subject over a period of 13 years and a mean duration of follow-up of 6 years in bakers and 8 years in non-exposed subjects. A respiratory health questionnaire was administered; occupational allergen skin prick tests, spirometry and a methacholine bronchial challenge test were performed at each visit. In each bakery, full-shift dust samples of the inhalable fraction were obtained in order to assess the exposure of each job assignment. The repeated measurements of BHR and FEV₁ were analyzed using mixed effects logistic and linear regression models in subjects seen at least twice.

BHR, respiratory symptoms and their simultaneous occurrence depended on the duration of exposure. FEV₁ significantly decreased with duration of exposure and BHR at a preceding visit. This result persisted when adjusting for the effect of BHR at the current visit. The measured exposure levels were not a significant predictor for any outcome. Occupational sensitization was only a predictor of a decline in FEV₁ when duration of exposure was not included.

In flour-exposed industrial bakers, length of exposure and smoking are long-term determinants of BHR and of the decrease in FEV₁. BHR at a preceding visit predicted lower FEV₁ even when accounting for the effect of BHR at the current visit.