Bronchoarterial ratio and bronchial wall thickness on high-resolution CT in asymptomatic subjects: correlation with age and smoking

OBJECTIVE: The purpose of this study was to determine whether the values of the bronchoarterial ratio and bronchial wall thickness, as viewed during high-resolution CT, relate to age and smoking status in asymptomatic healthy subjects. SUBJECTS AND METHODS: High-resolution CT was performed prospectively in 85 subjects without cardiopulmonary disease. The subjects were divided into three groups according to age: 29 subjects were 21-40 years old; 29 subjects, 41-64 years old; and 27 subjects, 65 years or older. Both bronchoarterial ratios, defined as the diameter of the bronchial lumen divided by the diameter of its accompanying artery, and the T/D ratio, defined as wall thickness (T) divided by the total diameter of the bronchus (D), were measured at the segmental and subsegmental levels of the apical and posterior basal segments. Each calculated ratio was evaluated according to age and smoking status. RESULTS: Significant correlation was found between the bronchoarterial ratio and age (r = 0.768, p < 0.0001), with the bronchoarterial ratio increasing with age and exceeding 1 in 41% of subjects older than 65 years. No significant correlation was seen between the T/D ratio and age. No significant differences in bronchoarterial ratio and T/D ratio were seen between smokers and nonsmokers in subjects overall; but in the elderly group, the T/D ratio was significantly higher in smokers than in nonsmokers (p = 0.021). CONCLUSION: The bronchoarterial ratio is influenced by aging. The normal bronchoarterial ratio in a substantial number of subjects older than 65 years overlaps with the ratio considered to represent bronchiectasis. Thus, when this ratio is used for the quantitative analysis of pulmonary and cardiovascular disease, the influence of age should be considered.