Analyze the following graphs and compare the rates at which loss of lung function occurs in sustained quitters, intermediate quitters and continuous smokers.[1]
FEV1 = forced expiratory volume in 1 second

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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