To estimate the prevalence and incidence of a disease and for the recruitment of patients into studies it is customary to use “operational” definitions that are agreed on, scientifically appropriate, simple, and practical. It is argued that the fixed ratio overdiagnoses obstruction in the elderly who may not have the disease. Perhaps a great example of similar reasoning is that of anemia. The World Health Organization (WHO) evaluates the prevalence of anemia using a fixed threshold value for men (13 g/dL) and for women (12 g/dL) independent of other factors, such as region of the world, race, or age (the factors most often used to argue against the fixed ratio).2 The prevalence of anemia in the elderly is 43% in the last WHO survey vs 21% for younger persons. Does this mean that anemia is being overdiagnosed? Or, like congestive heart failure, arterial hypertension, diabetes, mental function, visual acuity, and other diseases, is it possible that airflow limitation, just as the other conditions mentioned, increases as subjects age?