Thursday, February 13, 2020

Smokeless Tobacco Users Are Not Dying from Diseases Associated with Smoking

American health authorities for years failed to directly compare the health effects of smoking with those of smokeless tobacco (ST) use, as it would have meant acknowledging the large difference in deaths attributable to these products. 

That changed last year, when Altria’s Michael Fisher and colleagues published the first-ever follow-up mortality study of cigarette smokers and ST users, using the U.S. Government’s national surveys and National Death Index.

My colleague Nantaporn Plurphanswat and I conducted a similar study, which was published last fall in Harm Reduction Journal.  Like Fisher et al., we analyzed data for dipping/chewing and smoking participants from the eight years of National Health Interview Surveys (NHIS), between 1987 and 2010, in which ST users were counted.  The fact that the NHIS rarely calculated ST users suggests that the government didn’t think ST use was important.

We had access to cause-of-death information from federal data through 2015.  Smokers and ST users are always compared with never users of either product using the hazard ratio (HR), which is interpreted similarly to relative risk (i.e. a multiplier).  Current and former smokers are in the top two sections of each chart, while exclusive current ST users are highlighted by open green boxes.  Squares are men 40-59 years old; circles are men 60-79 years.

The first chart above displays results for all causes of death.  Note that current smokers have double the odds of death, while former smokers’ odds are elevated around 30% (It pays to quit!)  Also note the 44% elevation among current ST users, which is explained in the second chart (click on it for a larger version) with information about specific diseases.

Smokers have elevated death rates for all diseases.  They are twice as likely to die of heart diseases and cancer, and 6-13 times of respiratory diseases.  On the other hand, current exclusive ST users do not have significant elevations for any of these diseases

The third chart contains results divided into two mutually exclusive and exhaustive categories, smoking-related and everything else.  It shows that ST users’ death rates are primarily elevated by other causes; this is true especially among younger ST users, circled in red.  These causes included accidents, Alzheimer’s disease, kidney diseases, suicides and drug overdoses.      

Our analysis, studying only men age 40+ years, was designed to maximize the chance of finding significant results.  All previous studies had included women, who rarely use ST, and young men, among whom death is rare; those groups do not produce relevant information.  Consider: If a researcher wants to accurately measure the rate of breast cancer, they don’t count men.  Breast cancer occurs in men, but at such a minuscule rate that it would cut the rate among women in half, making it grossly inaccurate.

In summary, our study demonstrates that exclusive ST users do not demonstrate significantly elevated mortality from any smoking-related diseases.  Younger ST users, however, had elevated deaths from all other causes.  While we were unable to determine which specific diseases were involved, our findings for other causes are consistent with a recent CDC report and a recent study in JAMA showing increased mortality among adults age 25 to 64 years, which specified  drug overdoses, suicides and organ system diseases.


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