An observational study to assess changes in social inequality in smoking-attributable upper aero digestive tract cancer mortality among Canadian males between 1986 and 2001

Tobacco and low socioeconomic status have been acknowledged as potential risk factors for upper aero-digestive tract (UADT) cancers in North America. In context of reducing adult male smoking prevalence (by over 50%), in the past few decades in Canada, this study tried to document changes in smoking-attributable UADT cancer mortality rates, among Canadian males of different social strata, between 1986 and 2001. The contribution of smoking to UADT cancer mortality was estimated indirectly by using lung cancer mortality as an indicator of the accumulated mortality from smoking in a population. This method was applied to UADT cancer death rates of 35-69 year old socially stratified males. Data, stratified by neighborhood income quintile, could be obtained from Statistics Canada, for four census years, 1986, 1991, 1996, and 2001. A total of 2704 male deaths were analyzed. Between 1986 and 2001, UADT cancer deaths reduced by 30% (32 to 22 per 100,000) but the proportion of these deaths attributable to smoking reduced much more, by 41% (22 to 13 per 100,000). In the span of fifteen years, absolute social inequality (measured by rate difference between the highest and the lowest stratum) in smoking-attributable male UADT cancer mortality in Canada reduced by 47% and relative social inequality (measured by rate ratios) reduced by 9%. The present analyses reveal that between 1986 and 2001, smoking-attributable UADT cancer mortality rates among adult males (35-69 years) in Canada reduced in all social strata and the social inequalities in these rates have narrowed. Analysis of more current data will be of interest to confirm these trends.