Smoking Cessation, Not Reduction, Associated With Reduced CVD Mortality in T2DM

Smoking cessation, but not smoking reduction, was associated with decreased incidence of cardiovascular disease (CVD), all-cause mortality, and CVD mortality among patients with type 2 diabetes mellitus (T2DM), according to study findings published in Cardiovascular Diabetology.

Investigators explored the association between changes in smoking behavior and risk for CVD incidence and CVD/all-cause mortality among patients with T2DM.

An observational cohort study was conducted using data from the Korean National Health Insurance System, comprised of 349,137 patients with T2DM who smoked. A self-administered questionnaire was used to obtain information on smoking status and changes in smoking behavior.

Patients were categorized into 3 groups based on the number of cigarettes smoked per day: 1) light smokers (<10 cigarettes/day), 2) moderate smokers (10-19 cigarettes/day), and 3) heavy smokers (≥20 cigarettes/day).

Patients were then further categorized according to the difference in the number of cigarettes smoked per day from study enrollment to the end of the follow-up period: quitters (stopped smoking entirely), reducer I (≥50% reduction), reducer II (reduction from ≥20% to <50%), sustainers (reduction or increase <20%), and increasers (≥20% increase).

Newly diagnosed myocardial infarction (MI), ischemic stroke (IS), and mortality were the primary outcomes.

Mean patients age was 51.6 years and 95.2% were men. Median follow-up was 5.1 years.

Overall, 54.3% of participants were considered heavy smokers, 36.4% moderate, and 9.30% light.

The most common comorbidities overall included hypertension (45.2%), dyslipidemia (37.2%), and chronic obstructive pulmonary disease (25.1%).

During follow-up, investigators identified 6514 newly diagnosed cases of MI (1.9%), 7837 cases of IS (2.2%), and 14,932 mortalities (4.3%).

Patients categorized as quitters vs sustainers had a significantly decreased risk for MI (adjusted hazard ratio [aHR], 0.80; 95% CI, 0.75-0.86) and IS (aHR, 0.80; 95% CI, 0.75-0.85). Among patients categorized as reducers vs sustainers, no significant association was found for risk for MI (aHR, 1.03; 95% CI, 0.94-1.13) or IS (aHR, 1.00; 95% CI, 0.92-1.08). 

Lower all-cause mortality (aHR, 0.90; 95% CI, 0.86-0.94), lower MI mortality (aHR_, 0.79; 95% CI, 0.64-0.98) and lower IS mortality (aHR, 0.67; 95% CI, 0.47-0.95) were noted among patients categorized as quitters vs sustainers.

Study limitations included reduced generalizability, the small number of female smokers, potential unreliability of self-reported smoking behavior, and unmeasured confounding.

The study authors concluded, “To reduce CVD risk and all-cause mortality, and CVD mortality, smoking cessation should be achieved rather than smoking reduction.”