Despite increased risk for coronary artery disease and acute myocardial infarction (AMI), prior studies have found that smokers with AMI have lower mortality rates than nonsmokers, a phenomenon often termed ‘smoker’s paradox’. The present study was designed to examine the etiology of ‘smoker’s paradox’, especially with respect to the association with inflammation.
The subjects included 528 consecutive AMI patients who were admitted within 24 hours of onset and underwent successful coronary intervention. Of the 528 subjects, 232 (44%) were smokers.
The cardiac mortality rates over a 6 month period was significantly lower in the smoking group than the nonsmoking group (3% versus 9%, P = 0.01). There were significantly more male patients in the smoking group, and the smoking group was significantly younger than the nonsmoking group (P < 0.0001). The value of high sensitivity C-reactive protein (hs-CRP) on admission and 24 hours after onset, and serum amyloid A protein (SAA) were significantly higher, and acute phase BNP was significantly lower (hs-CRP on admission 1.36 ± 1.03 mg/dL versus 0.75 ± 0.82 mg/dL, P = 0.02, hs-CRP at 24 hours 3.86 ± 4.32 mg/dL versus 2.90 ± 3.46 mg/dL, P = 0.008, SAA; 288 ± 392 μg/dL versus 176 ± 206 μg/dL, P < 0.05, BNP; 248 ± 342 pg/mL versus 444 ± 496 pg/mL, P = 0.0002) in the smoking group than in the nonsmoking group. The early ST-segment resolution rate was higher in the smoking group compared with the nonsmoking group (80% versus 66%, P = 0.003).
The reason why smokers with AMI have lower mortality rates than nonsmokers, the so-called ‘smoker’s paradox’, is believed to be because smoking induces inflammation and smokers may have less damage to microvascular function after primary percutaneous coronary intervention.