Is smoking driving US and Canada social injustice trends? Smoke load/mortality rate associations across rising US and falling Canadian socioeconomic mortality disparities

Background: Both mortality rates and mortality rate excesses for the socioeconomically (SES) disadvantaged are high and rising for the United States and low and falling for Canada. Such mortality inequities present both dramatic contrasts of social injustice internationally and opportunities for estimating preventable contributions of smoking to rising and falling social mortality disparities and injustice in more developed nations. So I estimated cumulative tobacco smoke damage (smoke load)/mortality rate associations across recent US and Canada socioeconomic strata.

Methods: Published age adjusted mortality rates (rates) were used. Lung cancer rates were used as a smoke load proxy since smoking status overlooks smoking: years, depth, sensitivity, age, and other mortality-related aspects of smoke load. Univariate and multivariate lung cancer/other mortality rate regressions were run.

Results: Lung cancer rates were tightly associated with rates for all other mortality across socioecomic strata among both White males and females in the United States in 1993 and 2001 and in Canada in 1991, 1996, and 2001. Neither year nor income remained significantly associated with canadian male mortality rates after adjustment for smoke load.

Discussion. The tight associations seen between smoke load, as measured by lung cancer rates, and other mortality rates in multiple years, nations, and SES stratifications support prior findings that smoking can account for both the great majority of socioeconomic mortality rate disparities in Scottish men and 4.4 fold mortality rate disparities in narrow SES strata like nurses.