Self-reported smoking status and exhaled carbon monoxide in secondary preventive follow-up after coronary heart events: Do our patients tell the truth?

Abstract

Smoking cessation reduces the risk of myocardial infarctions (MI) and death in patients with coronary heart disease. Smoking status is frequently assessed based on self-report. The aims of this study were to compare self-reported and objectively measured (exhaled carbon monoxide [eCO]) smoking status after MI, percutaneous coronary intervention (PCI), and coronary artery bypass grafting (CABG), and to assess whether assumed wrongly declared smoking cessation was associated to poorer achievement of other treatment targets for secondary prevention. This study was a sub-analysis from a randomized controlled trial at Sorlandet Hospital, Arendal, Norway, 2007-2022, including patients hospitalized due to MI or after scheduled PCI/CABG, and primarily aimed at comparing secondary preventive follow-up in the outpatient clinic versus primary healthcare. Participants were followed up after the index event through outpatient consultations. Smoking status was assessed by self-report and by eCO (Smokerlyzer, Bedfont, UK) with concentration values ≥6 ppm interpreted as suggesting smoking. A total of 1540 participants aged 18-80 years were included in the main study. Self-reported smoking status and concomitant eCO measurement one year after the index event were available in 1291 (84%) participants. In all, Brussels, Belgium, from the 12th to the 13th of September 2024. The concentration of eCO was ≥6 ppm one year after the index event in 285 (22%) patients, and 72 (25%) of these patients reported non-smoking. Fewer patients with elevated eCO reporting non-smoking achieved the treatment target for blood pressure (<140/90 mmHg) in comparison to those reporting smoking (53% vs 68%, p=0.02). No differences for the other treatment targets for secondary prevention were found. The study indicates a need for objective measures for smoking cessation both in clinical studies and in clinical practice, and may indicate a lack of truthfulness regarding smoking habits. The study is registered on the official website of ClinicalTrials.gov. ID NCT00679237.