Change in FEV1 with aging

A general theoretical model of growth and decline of lung function with time. Curve A (red) shows normal change over time. Curve B (blue) indicates reduced lung growth and therefore a decrease in the peak level of lung function. Curve C (green) shows a premature decline in lung function, while Curve D (orange) depicts an accelerated decline in lung function. The horizontal gray line represents the development of COPD.