Respiratory symptoms and peripheral airways disease in a cross-sectional study on a random population sample

OBJECTIVES: Respiratory symptoms are associated with spirometry results but more strongly with smoking history, suggesting that alterations in the lung other than those revealed by spirometry contribute to cause symptoms. Smoking may cause obstruction of peripheral airways that is poorly detected by spirometry. The slope of phase III of the single-breath nitrogen (N(2)) test detects smoking-induced alterations in smokers before spirometry is impaired. The aim of the present investigation was to study the association between respiratory symptoms and the slope of phase III adjusting for spirometry results and smoking history. DESIGN: Single-centre retrospective cross-sectional study. SETTING: University hospital in Gothenburg, Sweden. PARTICIPANTS: A random population sample of 430 elderly men. METHODS: The presence of seven different respiratory symptoms were analysed by a multiple logistic regression model in relation to spirometry results, smoking history (pack-years) and the slope of phase III in a population sample of 430 elderly men, age span 50–67 years. Furthermore, smoking normalised values of the slope of phase III were calculated and differences between subjects reporting/not reporting symptoms were tested. RESULTS: The presence of some cough symptoms was significantly associated with a steep slope of phase III also when adjusting for spirometry results and smoking history. Furthermore, smoking normalised slope of phase III was significantly steeper among subjects with cough symptoms compared to those without cough symptoms. CONCLUSIONS: Cough symptoms may be an effect of abnormalities in peripheral airways at least among elderly men.