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Smoking Cessation, Not Reduction, Reduces CVD Events
Quick Takes
- Smoking cessation is associated with a lower risk for stroke and MI.
- Smoking reduction has a similar risk for stroke or MI to that of continued smoking.
Study Questions:
Does smoking cessation or reducing smoking lower the risk for cardiovascular disease (CVD)?
Methods:
Data from the South Korean universal health insurance system (NHIS) were used for the present analysis. NHIS covers approximately 97% of the population. NHIS recommends that all adults ages ≥40 years complete a general health examination every 2 years, including a questionnaire on lifestyle habits. NHIS is linked to health care utilization data. Data on smoking behaviors assessed in 2009 and 2011 were used to assess changes in smoking. Adults diagnosed with cardiovascular disease (CVD) or cancer prior to the second exam were excluded. Participants who were diagnosed with stroke (n = 2,487) or myocardial infarction (MI) (n = 1,466) or who died (n = 3,494) within 1 year after the second health examination period were also excluded to reduce the effect of revised causality. Individuals who were missing data were also excluded. Smoking status was grouped into quitters, reducers (either ≥50% or 20-50% reduction), sustainers, and increasers (increased smoking by ≥20%).
Results:
A total of 897,975 current smokers ages ≥40 years who completed two NHIS exams (in 2009 and 2011) were included in the present analysis. Of these participants, 20% were quitters, 45.7% were sustainers, and 14.5% were increasers. Among those who reduced smoking, 7.3% reduced smoking by ≥50%, and 11.6% reduced smoking by 20-50%. During 5,575,556 person-years (PY) of follow-up, 17,748 stroke (3.2/1,000 PY) and 11,271 MI (2.0/1,000 PY) events were identified. Quitters had significantly decreased risk of stroke (adjusted hazard ratio [aHR], 0.77; 95% confidence interval [CI], 0.74–0.81; absolute risk reduction [ARR], -0.37; 95% CI, -0.43 to -0.31) compared to sustainers after adjustment for demographic factors, comorbidities, and smoking status. Quitters also reduced their risk for MI (aHR, 0.74; 95% CI, 0.70–0.78; ARR, -0.27; 95% CI, -0.31 to -0.22) compared to sustainers after adjustment. The risk of stroke and MI incidence in reducers who reduced smoking by ≥50% was not significantly different from the risk observed for those who sustained smoking (aHR, 1.02; 95% CI, 0.97–1.08 and aHR, 0.99; 95% CI, 0.92–1.06, respectively). Those who reduced smoking by 20-50% had the same risk for stroke or MI as those who sustained smoking. Among a subgroup who underwent a third examination (in 2013), those who quit at the second examination (2011) but had started smoking again by the third examination had a 42–69% increased risk of CVD compared to sustained quitters.
Conclusions:
The investigators concluded that smoking cessation, but not reduction, was associated with reduced CVD risk.
Perspective:
These data from a large cohort support the advice to quit smoking entirely. Furthermore, reducing smoking, even significant reductions in smoking, does not appear to lower risk for CVD events.
Clinical Topics: Cardiovascular Care Team, Prevention, Smoking
Keywords: Comorbidity, Life Style, Myocardial Infarction, Primary Prevention, Risk, Smokers, Smoking, Smoking Cessation, Smoking Reduction, Stroke, Tobacco Smoking, Universal Health Insurance, Vascular Diseases
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