There is no doubt that the main risk factor for chronic obstructive pulmonary disease (COPD) is cigarette smoking. Much remains to be determined, however, concerning the pathogenesis of this disease. One of the most important questions is why only 10% to 20% of chronic heavy smokers develop COPD.<sup>31 Fletcher C., Peto R., Tinker C. , e al. The Natural History of Chronic Bronchitis: An Eight-Year Study of Chronic Obstructive Lung Disease in Working Men in London Oxford: Oxford University Press (1976).  272

Cliccare qui per andare alla sezione Riferimenti</sup> There is clearly a relationship between smoking history and decline in lung function,<sup>5 Beck G.J., Doyle C.A., Schachter E.N. Smoking and lung function Am Rev Respir Dis 1981 ;  123 : 149

Cliccare qui per andare alla sezione Riferimenti</sup> but smoking habits (i.e., pack years and duration of smoking) were estimated to account for only approximately 15% of the variation in forced expiratory volume in 1 second (FEV₁) levels.<sup>5 Beck G.J., Doyle C.A., Schachter E.N. Smoking and lung function Am Rev Respir Dis 1981 ;  123 : 149

Cliccare qui per andare alla sezione Riferimenti</sup> Other factors therefore must contribute to the development of COPD. Environmental risk factors such as childhood viral respiratory infections, latent adenoviral infections, and air pollution have been identified. There are also genetic factors that influence susceptibility to the detrimental effects of cigarette smoke and therefore to COPD.<sup>78 Sandford A.J., Weir T.D., Paré P.D. Genetic risk factors for chronic obstructive pulmonary disease Eur Respir J 1997 ;  10 : 1380  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup>