Author + information
- Man Ping Wang, PhD,
- Jing Chen, PhD,
- Tai Hing Lam, MD∗ (, )
- Chu Pak Lau, MD and
- Sophia S. Chan, PhD
- ↵∗School of Public Health, University of Hong Kong, Sassoon Road, Pokfulam, Hong Kong 852
Secondhand smoke (SHS) may act as a smoking cue and prime dose of nicotine by activating acetylcholine receptors in brains to trigger smoking (1). SHS exposure at home and having a smoking spouse or peers predicted a lower likelihood of smoking cessation in cancer patients (2). Similar cross-sectional findings were found in cardiac patients (3). This study prospectively investigated the roles of SHS exposure at home and outside of the home on smoking cessation among cardiac outpatients in Hong Kong (19.1% of men and 3.1% of women smoked daily in 2012).
We used data from a randomized controlled trial, which found no difference in smoking cessation between stage-matched intervention and control groups (4). A total of 1,495 (80.4%) adult smokers attending the cardiac outpatient clinics in major hospitals in Hong Kong were interviewed and followed for up to 12 months. SHS exposure at home was reported at baseline and categorized as none, ≤1 h/day, and >1 h/day. The number of smoking family members and exposure to SHS outside of the home were categorized as none and any. Smoking cessation was defined as self-reported abstinence in the past 30 days at 12-month follow-up. Sociodemographic characteristics, alcohol drinking, smoking quantity and duration, long-term medication use, and cardiac surgery received were recorded and treated as potential confounders. The associations of having smoking family member(s), SHS exposure at home, and SHS exposure outside of the home with smoking cessation were analyzed adjusting for intervention allocation (Model 1), demographic characteristics and smoking behaviors (Model 2), and clinical variables (Model 3) using logistic regressions to yield adjusted odds ratios (AORs).
The subjects (91.2% male, mean age 59 ± 13.7 years) smoked for an average of 39.3 ± 15.1 years and consumed cigarettes for 41 ± 27.4 pack-years. Having smoking family member(s) (24.3%) was associated with a lower AOR of 0.64 (95% confidence interval: 0.49 to 0.83) for smoking cessation, with the same effect size after adjusting for various potential confounders in different models (Table 1). Any SHS exposure at home (20.2%) was associated with an AOR of 0.65 (95% confidence interval: 0.48 to 0.89) for smoking cessation, and increasing duration of SHS exposure at home was associated with decreasing odds of smoking cessation (p for trend <0.001). SHS exposure outside the home (89.6%) was not significantly associated with smoking cessation. Repeated analyses using 7-day abstinence as smoking cessation yielded similar results (data not shown).
We found a prospective, dose-response, and robust association between SHS exposure at home and lower likelihood of smoking cessation in cardiac outpatients. The magnitude of the association was in line with our studies on adolescents, but is smaller than studies on patients with cancer (AOR: 0.19 to 0.25) and coronary heart disease (AOR: 0.26) (2,3), probably due to the difference of research design, SHS measurement, and disease status of patients. SHS exposure outside of the home in our subjects was likely and mostly from indoor workplaces, restaurants, and streets where the exposure should be less intense than at home. This may explain the nonsignificant association between SHS exposure outside of the home and smoking cessation.
Smoking cessation is one of the most effective strategies for primary and secondary prevention of cardiovascular disease (CVD), but it has received far less attention than other CVD risk factors, such as hypertension, hyperlipidemia, and diabetes (5). Cardiologists play an important role in assisting smokers to quit, particularly at the teachable moments of CVD diagnosis and hospitalization. Current practice guidelines for smoking cessation on the basis of evidence from pharmacological and behavioral trials achieved <50% abstinence at 12-month follow-up. In addition to standard smoking cessation practices, cardiologists should assess SHS exposure in smokers and advise smokers to avoid being exposed to SHS and smoking cues. Including family members in smoking cessation counseling may be warranted, particularly for CVD patients who usually require lifestyle and behavioral modifications using a family-centered approach. Future interventions including counseling on SHS reduction may produce extra beneficial effects on smoking cessation in cardiac patients, in addition to the beneficial effects of avoiding SHS on cardiovascular function in smokers.
All information was self-reported and subject to reporting bias. Using biological markers of SHS exposure could not distinguish places of exposure, which were differentially associated with smoking cessation. The generalizability of this study might be limited, as it was originally designed as a trial and adopted a nonrandom sampling method, although the subjects were screened on the basis of a large pool of patients (n = 60,588).
We found that SHS exposure at home was associated with a lower likelihood of smoking cessation among cardiac outpatients. Interventions to reduce SHS exposure may increase quitting among cardiac patients.
Please note: This study was supported by a Competitive Earmarked Research Grant (HKU7224/01M) by Research Grants Council, Hong Kong. The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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