Effects of daily cigarette consumption on respiratory symptoms and lung function in a general population sample of North-Italian men

We assessed the respiratory effects of the number of cigarettes smoked daily (CIGD) in 748 male smokers of a general population sample living in the unpolluted area of the Po Delta (Italy). A standardized questionnaire, flow-volume curves (V/V), the diffusing capacity of carbon monoxide (DLCO) and the slope of the alveolar plateau of nitrogen (DN2%/l) were used. Subjects were divided according to the median value of the observed distribution of CIGD (1-19, 20+) and according to the tertile values of the observed distribution of pack-years (an index representing lifetime cigarette consumption; 1-7, 8-21, 22+). In those with a higher CIGD, the prevalence rate of chronic phlegm was always significantly increased, while the prevalence rate of wheeze was significantly higher if they had smoked 8+ pack-years. Using analysis of variance, adjusted for pack-years, DLCO indexes, FEF75-85 and V(max75) were significantly reduced in those with higher CIGD. When multiple logistic models, accounting for the independent effects of age and pack-years, were used, significantly increased odds ratios (ORs) for symptoms (e.g. OR = 2.0 for phlegm, OR = 1.8 for cough, OR = 1.6 for wheeze) and abnormal :DLCO (OR = 1.9) or DN2%/l (OR = 1.6) were associated with a daily consumption of 10 cigarettes. In conclusion, the amount of cigarettes currently smoked may add a negative effect to that caused by lifetime cigarette consumption on respiratory symptoms and lung function. Moreover, the use of diffusing capacity in general population surveys is advisable.