Effects of cigarette smoking on older chinese men treated with clopidogrel monotherapy or aspirin monotherapy: a prospective study

We investigated the comparative effects of smoking status on outcomes in older Chinese men receiving aspirin or clopidogrel monotherapy. This was a prospective observational study of outcomes in 668 men aged ≥ 60 years undergoing annual health examination in the Chinese People's Liberation Army General Hospital from March-April 2017. All patients received regular treatment with aspirin or clopidogrel. Platelet aggregation and phenotyping for rs762551 were measured in all patients. We recorded all major adverse cardiovascular and cerebrovascular events; namely, all-cause death, myocardial infarction, stroke, transient ischemic attack, and unstable angina. In the clopidogrel subgroup, homozygous carriers (AA) of the CYP1A2*1F gene (rs762551, 163C>A) appeared more frequently in smokers than in nonsmokers (45.6% vs 32.7%, p = .035). Adenosine diphosphate-induced platelet aggregation using light transmittance aggregometry was lower in smokers compared with nonsmokers (44.97 ± 20.05% vs 51.98 ± 19.38%, respectively; p = .0018). Smokers (n = 103) had a decreased risk of major adverse cardiovascular and cerebrovascular events, compared with nonsmokers [n = 159; hazard ratio, 0.466; 95% confidence interval: 0.262-0.829, p = .008]. In the aspirin subgroup, AA-induced platelet aggregation showed no significant difference regarding smoking vs nonsmoking status (30.90 ± 32.21 vs 29.78 ± 31.47, respectively; p = .771). However, we saw a significant increase in adverse clinical events in the smoking group (n = 148) compared with the nonsmoking group (n = 258; hazard ratio = 1.907, 95% confidence interval: 1.128-3.225; p = .016). In older Chinese men, active smokers benefitted from clopidogrel therapy compared with aspirin. Long-term cigarette smoking may contribute to increased variations in CYP1A2*1F, but the variations do not fully explain the smoking paradox.

The effect of smoking on residual platelet reactivity to clopidogrel: a systematic review and meta-analysis

Cigarette smoking is an important cardiovascular risk factor, causing morbidity and mortality. There are many original studies on the impact of smoking, but its influence on platelet ADP-P2Y12 receptor inhibitors lack consistency. Thus, we conducted a systematic review and meta-analysis of already existing data/studies to further explore this issue. PubMed, Web of science, EMBASE, Clinical Trials, and the Cochrane Library were searched from inception to March 2018. Studies investigating the residual platelet reactivity categorized by smoking status and patients treated with platelet ADP-P2Y12 receptor inhibitors qualified the inclusion criteria. The primary outcome was P2Y12 reaction unit (PRU) value measured by VerifyNow P2Y12 assay, compared with different smoking status in ADP-P2Y12 receptor inhibitors treatment groups. Secondary outcome was post-treatment with 5 μmol/L ADP-inhibition of platelet aggregation (ADP-IPA) measured by light transmittance aggregometry (LTA). Of the 4954 citations retrieved, 12 studies involving 16 296 patients with acute coronary syndrome and/or stent deployment using platelet ADP-P2Y12 receptor inhibitors were included for meta-analysis. Pooled analysis revealed that PRU values of current smokers were 25.70 lower than nonsmokers (95% CI -38.81 to -12.60, p = 0.0001), getting better effects of antiplatelet treatment. In the smoking extent subgroup analysis, patients smoking >10 cigarettes/day shown about 46.49 lower of PRU values than patients smoking <10 cigarettes/day (p < 0.00001). Racial subgroup analyses found that smokers had increased platelet inhibition in the Caucasian population. Further, pooled analysis of ADP-IPA values for 1658 patients from five studies showed a significantly lower residual platelet reactivity in current smokers compared to that in nonsmokers (MD = -4.19; 95% CI -6.55 to -1.83; p = 0.0005). This systematic review and meta-analysis suggested that smokers have increased platelet inhibition and lower aggregation in response to clopidogrel than nonsmokers. These residual platelet reactivity observations may help to explain differential clinical outcomes in smokers vs. nonsmokers in large scale clinical trials.