Analyze the following graphs and compare the rates at which loss of lung function occurs in sustained quitters, intermediate quitters and continuous smokers.
FEV1 = forced expiratory volume in 1 second
1. Anthonisen NR, Connett JE, Kiley JP, et al: Effects of smoking intervention and the use of an inhaled anticholinergic bronchodilator on the rate of decline of FEV1. The Lung Health Study. JAMA 1994;272:1497-1505