Aims: To study the prevalence of airway obstruction according to age, gender and smoking habits using spirometry, and to compare the results using different definitions, classifications and spirometric reference values in an elderly population.
Methods: A random sample of 2046 men and women in nine age cohorts (aged 60, 66, 72, 78, 81, 84, 87, 90 and 93 years) were drawn from the Swedish municipality registers. 1092 subjects performed spirometry of which 574 met ATS spirometric criteria.
Results: According to GOLD criteria (FEV1/FVC <0.7) the prevalence of obstruction was 22.5% regardless of which one of three different spirometric reference values were used. Using the recently-changed Swedish National Guideline (SNG) recommendations--an FEV1/(F)VC ratio<0.7 in subjects younger than 65 years but an FEV1/(F)VC ratio<0.65 in subjects 65 years or older in order to define airway obstruction--the prevalence was 14.1% regardless of the applied spirometric reference values. Using the criterion FEV1/(F)VC < expected for age and gender (i.e. lower limit of normal, LLN) yielded the lowest prevalence of 10.1%.
Conclusions: The prevalence of pulmonary obstruction depends on the criteria used for defining airway obstruction and on which spirometric normal values are applied. Using an age-adjusted FEV1/(F)VC LLN quotient to define pulmonary obstruction can be recommended on the basis of our results.