MAIN OBJECTIVE: To document and assess the current health impact of non-neoplastic lung disease (NNLD) in Canadian men and women that is attributable to smoking. DESIGN: Comparison of three recent studies providing estimates of smoking-attributable deaths, potential years of life lost, hospital separations and hospital days due to NNLD in Canada. Review of recent epidemiological studies providing relative risk estimates of smoking-attributable mortality and morbidity for chronic obstructive pulmonary disease and pneumonia, including a meta-analysis. MAIN RESULTS: Each year at least 6700 Canadian men and women die from NNLD attributable to smoking. Smoking-attributable NNLD deaths in men outnumber those in women by about 2 to 1. The majority of these deaths are due to chronic obstructive pulmonary disease, which is exceeded in importance as a smoking-attributable cause of death only by lung cancer and ischemic heart disease. NNLD accounts for about 20% of all smokingattributable deaths in Canada, 14% of the potential years of life lost due to smoking, and 22% and 25% of all smokingattributable hospital separations and hospital days, respectively. Long term follow-up assessments of large cohorts suggest that the impact of smoking on health has been underestimated. Recent studies also suggest that women may be more susceptible than men to the adverse effects of smoking on lung function. CONCLUSION: NNLD caused by smoking has an important health impact in Canada. Tobacco control strategies must be enhanced. Key Words: Lung diseases, Morbidity, Mortality, Smoking Le tabagisme et la maladie pulmonaire non cancéreuse chez les Canadiens et Canadiennes OBJECTIF PRINCIPAL : Documenter et évaluer les influences actuelles sur la santé de la maladie pulmonaire non cancéreuse chez des Canadiens et Canadiennes, et qui sont imputables au tabagisme. MODÈLE : Comparaison de trois études récentes fournissant des estimés des décès attribuables au tabagisme, des années potentielles de vie perdues, des congés donnés aux patients hospitalisés et des journées d'hospitalisation dus à la maladie pulmonaire non cancéreuse au Canada. Revue des études épidémiologiques récen-tes fournissant des estimés du risque relatif de la mortalité attribuable au tabagisme et de la morbidité liée à la maladie pulmonaire obstructive chronique et à la pneumonie, incluant une méta-analyse. voir page suivante I t is now well established that smoking is the most important preventable cause of premature mortality and morbidity in Canadian men and women (1,2), as it is in the populations of other developed countries (3,4). At least 33,000 Canadians die each year as a result of tobacco use, which also accounts for more than 200,000 hospital separations, three million hospital days and some $9.5 billion in costs from lost productivity and direct health care expenditures (2). Despite this enormous health toll, smoking remains prevalent. Estimates from the National Population Health Survey conducted in 1994 indicate that 6.9 million Canadians, 31% of the population aged 15 years and over, smoke (5). Further, rates of smoking among young Canadians, after some years of decline, have now plateaued (6) and may actually be increasing in some provinces, notably in Ontario The primary purpose of this paper is to document and assess current estimates of the health impact of smoking in Canada with regard to non-neoplastic lung disease (NNLD) and to point out some limitations of these data. As well, recent reports concerning long term epidemiological studies of the relationship of smoking to NNLD are reviewed, including a meta-analysis of relative risk estimates. Attention is drawn to recent studies that indicate the possibility that the lungs of women may be particularly susceptible to the adverse effects of tobacco smoke. HEALTH IMPACT OF SMOKING DUE TO NNLD Smoking-attributable mortality: Three studies provide estimates of the current mortality impact of tobacco use in Canadian men and women Makomaski Illing and Kaiserman (1), using risk estimates from the same source, concluded that in 1991 there were more than 8100 NNLD deaths among Canadians attributable to smoking, out of a total of 41,408 smoking-attributable deaths. Most recently, Single et al (2) used mortality estimates derived from a meta-analysis of epidemiological studies conducted by English et al (10), discussed further below. They concluded that in 1992 NNLD deaths in Canadians attributable to smoking exceeded 6700, out of a total estimate of more than 33,000 smoking-attributable deaths. In all three estimates shown in Comparability of the mortality estimates: Because the RISKS OF NNLD MORTALITY AND MORBIDITY ASSOCIATED WITH SMOKING Mortality: A study by Canadian investigators was among the first to document the excess risk of mortality from NNLD in smokers compared with nonsmokers (11,12). In the final six-year follow-up study of some 78,000 male veterans, initiated in 1955 by the Department of National Health and Welfare (12), it was found that veterans with a lifetime history of smoking cigarettes had about 11 and eight times the risk of mortality from chronic bronchitis and emphysema, respectively, compared with nonsmokers. A dose-response relationship between the amount smoked daily and the risk of mortality was also observed. For pneumonia and influenza there was a small increase in relative risk (1.4). Since then, a host of epidemiological studies from many countries have confirmed the causal relationship between smoking and COPD in both men and women, as well as a small increase in the risk of mortality from pneumonia (13-17). Doll et al Doll et al Recently, Gold et al (27), in a study of the effects of cigarette smoking on the level and rate of growth of pulmonary function in large cohorts of adolescent boys and girls, demonstrated that the growth of lung function in association with smoking was more severely affected in the girls. This finding is particularly worrisome in the context of the ages at which adolescent girls and boys begin to smoke. In the 1994 Canadian Youth Smoking Survey (6) it was found that although the rates of beginning to smoke were similar in boys and girls ages 10 to 12 years (4% in each), by ages 13 to 14 years this rate was significantly higher than girls (15%) compared with boys (9%). Girls may not only be more susceptible to the adverse effects of smoking, but they appear to be getting a 'head start' on this addiction. While sex differences in susceptibility to the smokinginduced changes in lung function require more study, particularly with regard to underlying biological mechanisms, the primal importance of smoking cessation in reducing the age-related decline in FEV 1 in smokers with mild obstructive pulmonary disease is beyond disput
