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Evidence for Smoking Cessation after Cardiovascular Events – Part 1

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Smoking cessation is difficult, and it remains so even after life-threatening cardiovascular events. In fact, systematic reviews have reported smoking cessation rates averaging around 50% in patients with coronary heart disease. This statistic is clearly reflected in the papers which we will be going through in the first 2 parts of this short series on smoking cessation. 

 

Exactly how important is smoking cessation after cardiovascular events? 

Is there an urgency in quitting?

What numbers can we present to our patients? 

Or rather, are we, as healthcare professionals (HCPs) ourselves, convinced about what we are advocating? 

The papers in parts 1 and 2 of this four-part series, summarise the evidence for smoking cessation after cardiovascular events, dated chronologically from old to the most recent. All papers were observational cohort studies as it is unethical to subject a particular arm to continue smoking as with randomised controlled trials (RCTs). Hence, a drawback of the following evidence could possibly be a lack of randomization and unequal distribution of important prognostic variables. 

STUDY 1: Cessation of Smoking after MI. Effects on Mortality after 10 years.1 Aberg. An et al. (1983) 

Population: 

983 Swedish male smokers (≥ 1 cigarette/day, ≥ 3 months), aged ≤ 67 on recruitment, followed up for a maximum period of 10.5 years, after their first myocardial infarct (MI). 

Intervention:

45% persistent smokers (441); 55% stopped smoking (542) 

Comparator: 

The primary outcome was death by coronary heart disease, and the secondary outcome was non-fatal reinfarction 

Outcome: 

After 5 years, statistically significant results showed that the cumulative survival rate was 84% for quitters compared to 78% for those who continued (p<0.02). 

In fact, for patients < 50 years old, a statistically significant difference in mortality was evident within 3 years. Naturally, rapid beneficial effects were observed with regards to lethal arrhythmias, change of platelet adhesiveness, and of myocardial metabolism, rather than progressive changes in coronary arteries. 

75% survival was reached only after 115 months for those who stopped, as compared to 71 months for those who continued, conferring a difference of 3 years as well. 

Cumulative reinfarction rates were 21% for those who stopped, and 30% for those who continued to smoke. (p < 0.02)

The differences between smokers and non-smokers, based on these percentages might not seem significant in hindsight, but it may be because this study was conducted in an era before the advent of PCI and guidelines guiding appropriate medical therapy post-acute coronary syndromes (ACS). These factors could have led to poorer outcomes in general, regardless of smoking status. 

 

STUDY 2: Three Life Years gained from smoking cessation after CABG: a 30-year follow-up study.2 Van Domburg, RT et al. (2008) 

Population: 

551 smokers (aged ≥ 51 years, 92% male) who successfully underwent coronary artery bypass graft (CABG) surgery, for a median follow-up of 29 years. 

Intervention:

57% persistent smokers; 43% stopped smoking 

Comparator: 

The primary outcome was death by coronary heart disease, and the secondary outcome was non-fatal reinfarction 

Outcome: 

There were significant differences favouring the group who quit smoking when it came to survival rates. And after adjustment for all possible confounders, smoking cessation remained a significant predictor of lower mortality at a hazard ratio of 0.6 (95% CI 0.48-0.72)or almost half, compared to those who continued smoking. 

The cumulative 10-, 20-, and 30-year survival rates were 88%, 49%, and 19%, respectively, in the group of patients who quit smoking, and only 77%, 36%, and 11%, respectively, in the persistent smokers (P < .0001). 

It also showed that quitting smoking could add a significant 3 years more to your life expectancy. Life expectancy in the quitters was 20.0 years and 17.0 years in the persistent smokers (P < .0001) = difference of 3 years.

Whether or not that’s significant, depends again on perspective. However, it remains clear that smoking cessation does confer clear benefits when it comes to patients with cardiovascular disease. 

Follow our social media channels linked below, to get the latest updates on part 2 of this series, where we’ll be going through two more studies that are slightly more contemporary than the two that we’ve just gone through. Hopefully, with clearer insight and applicable data points that we as HCPs could probably use to steer us, and our patients onward in our journey towards smoking cessation. 

 

References: 

  1. Aberg, A., Bergstrand, R., Johansson, S., Ulvenstam, G., Vedin, A., Wedel, H., … Wilhelmsen, L. (1983). Cessation of smoking after myocardial infarction. Effects on mortality after 10 years. British heart journal, 49(5), 416–422. doi:10.1136/hrt.49.5.416
  2. Van domburg RT, Op reimer WS, Hoeks SE, Kappetein AP, Bogers AJ. Three life-years gained from smoking cessation after coronary artery bypass surgery: a 30-year follow-up study. Am Heart J. 2008;156(3):473-6.

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