The article by Mannino and Diaz-Gutzman1 in CHEST (January 2012) reiterates an argument previously published by Mannino et al2 suggesting that the use of a fixed ratio of 0.7 for FEV1/FVC is justified in defining the presence of airflow obstruction because it identifies people who are at increased risk of dying. However, this misconstrues the true relationship between lung function and risk of death, which is a continuum.3 For FEV1 data, people with lung function just above their predicted value have an increased mortality when compared with those with the very best function. For FEV1/FVC, the risk is increased as soon as the level of function goes below predicted. If one was justified in using lung function to support the definition of a disease state on the basis of associated increased mortality, then at least one-half of the population would be diagnosed with the disease, which is clearly not meaningful. Furthermore, the approach by Mannino and Diaz-Gutzman1 of looking at those considered “abnormal” by the fixed ratio, but above the lower limit of normal (LLN), identifies an older age group (Table 3 of the article, mean age 67.9 years, SD 0.9), and this population will consequently have a higher mortality because age was not included in their model. The findings presented in this article could be demonstrated in endless other data sets, but this does not mean the argument by Mannino and Diaz-Gutzman1 is correct because it conveniently ignores the true relationship between lung function, age, and mortality.