From the Authors: We thank Dr. Stanescu for his interest in our article describing the association between baseline lung function measurements and longitudinal lung function decline and mortality in over 5,800 smokers from the Lung Health Study (1). Dr. Stanescu and colleagues’ prior publication of 13-year follow-up of 56 smokers and ex-smokers (2) was an important foundation for our analysis. We agree that there is substantial heterogeneity in lung function decline, and a single baseline measure does not necessarily predict excessive decline in all persons. Although the individual risk for excessive lung function decline may not be completely predicted by a single measure, our analysis identifies a high-risk population at risk for complications from chronic obstructive pulmonary disease. We do think our analysis includes adequate follow-up to draw meaningful conclusions, as our primary association between lower baseline lung function and excessive decline was observed with both 5-year and 11-year follow-up data, as described in the article and online supplement. Our data do not support using a lower threshold than FEV1/FVC < 0.60 for accelerated decline (such as FEV1/FVC < 0.45 as suggested by Dr. Stanescu). Unfortunately, we did not collect nitrogen slope of the alveolar plateau (N2 slope) data, so we cannot determine if this would add to the prediction of lung function decline.