Abstract
BACKGROUND: The choice between lower limit of normal or fixed value of forced expiratory volume in one second/forced vital capacity ratio (FEV(1)/FVC) < 0.70 as the criterion for confirming airway obstruction is an open issue. In this study, we compared the criteria of lower limit of normal and fixed FEV(1)/FVC for diagnosis of airway obstruction, with a focus on healthy elderly people. METHODS: We selected 367 healthy nonsmoking subjects aged 65-93 years from 1971 participants in the population-based SARA (Salute Respiratoria nell'Anziano, Italian for "Respiratory Health in the Elderly") study, analyzed their spirometric data, and tested the relationship between spirometric indices and anthropometric variables. The lower limit of normal for FEV(1)/FVC was calculated as the fifth percentile of the normal distribution for selected subjects. RESULTS: While FEV(1) and FVC decreased significantly with aging, the relationship between FEV(1)/FVC and age was not statistically significant in men or women. The lower limit of normal for FEV(1)/FVC was 0.65 in men and 0.67 in women. Fifty-five participants (15%) had FEV(1)/FVC < 0.70 and would have been inappropriately classified as obstructed according to the Global Initiative for Obstructive Lung Disease, American Thoracic Society/European Respiratory Society, and Canadian guidelines on chronic obstructive pulmonary disease. By applying different FEV(1)/FVC thresholds for the different age groups, as previously proposed in the literature, (0.70 for <70 years, 0.65 for 70-80 years, and 0.60 for >80 years) the percentage of patients classified as obstructed decreased to 6%. No subjects older than 80 years had an FEV(1)/FVC < 0.60. CONCLUSION: The present results confirm the inadequacy of FEV(1)/FVC < 0.70 as a diagnostic criterion for airway obstruction after the age of 65 years. FEV(1)/FVC < 0.65 and <0.67 (for men and women, respectively) could identify subjects with airway obstruction in such a population. Further reduction of the threshold after 80 years is not justified.