Quitting smokeless tobacco after MI almost halves mortality

Arefalk G, Hambraeus K, Lind L et al.,
Circulation. 2014 Jun 23. pii: CIRCULATIONAHA.113.007252. [Epub ahead of print]

Background

Oral moist snuff is a form of smokeless tobacco, of which the use is increasing worldwide. In Sweden, 20% of male and 3% of the female adult population use snus, the Swedish form of snuff, on a daily basis. Cardiovascular effects of smokeless tobacco have not been studied extensively, but acute autonomic and hemodynamic effects such as endothelial dysfunction [1,2], increased blood pressure, heart rate and blood levels of adrenaline [3,4] have been described. Contradicting results have been published on a possible higher risk of (fatal) myocardial infarction (MI), including suggestions that snus may predispose to arrhythmic or other serious complications of MI.
This study aimed to evaluate whether snus users who experience an MI benefit from discontinuation of snus use. Data from the Swedish SWEDEHEART nation-wide quality register were used. A prospective sample of patients with a recent MI were included. The primary study sample included all subjects who were using snus at the time of MI, and a second sample included those who were smoking at the time of MI. Median follow-up time was 1.9 years, with a maximum of 4.9 years (total 40370 person-years at risk (PYAR)).

Main result

• 83 participants died during follow-up. The incidence rate for post-MI snus quitters was 9.7 (95%CI: 5.7-16.3) /1000 PYAR, while for post-MI snus users it was 18.7 (95%CI: 14.8-23.6) /1000 PYAR.
• In a model adjusted for age and gender, snus quitters had almost 50% lower mortality rate than continued users (HR: 0.51, 95%ci: 0.29-0.91). Even after further correction for past and present smoking exposure, snus use discontinuation post-MI was independently associated with a lower rate of total mortality than continued use (HR: 0.55, 95%CI: 0.30-0.97).
• Age-adjusted mortality incidence rate for post-MI smoke quitters was 13.5 (95%CI: 11.3-16.2) /1000 PYAR and 28.4 (95%CI: 24.2-33.3) /1000 PYAR for those who continued to smoke. Mortality was about 50% lower in smoke quitters than in those who continued to smoke (HR: 0.50, 95%CI: 0.39-0.63). Adjusting for past and present snus use essentially did not change the results (HR: 0.50, 95%CI: 0.39-0.63).
• In a model adjusted for age, gender, past and present smoking, occupation status and participation in a cardiac rehabilitation program, a HR of 0.37 (95%CI: 0.05-2.9) was seen for snus quitters, HR: 0.59 (95%CI: 0.28-1.24) for smoke quitting and HR: 0.31 (95%CI: 0.10-0.98) for  dual quitting, relative to not quitting either tobacco form.

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Conclusion

In this large prospective cohort, discontinuation of snus use after a MI, was associated with nearly half the mortality risk, irrespective of many other relevant covariates. The benefit of quitting this form of smokeless tobacco after an MI was similar to the undisputed benefit of smoking cessation, which was confirmed in this study. 

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References

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