ReviewCigarette smoking: An undertreated risk factor for cardiovascular disease
Introduction
Cardiovascular disease (CVD) is the leading cause of death in many developed countries. In 2000, CVD was directly responsible for more than 4.35 million deaths in Europe, 1.9 million of them in the European Union, accounting for 43% of all deaths in men and 55% of all deaths in women [1]. CVD may also become the leading cause of death in developing countries which currently bear 80% of its global burden [2].
Smoking is one of six major modifiable risk factors for CVD. Conversely, CVD is the leading cause of death from smoking (Table 1) [3], [4], [5], [6]. In some regions, including South America, Eastern Europe, and South-East Asia, there were approximately twice as many smoking-attributable deaths from CVD as there were from lung cancer or respiratory diseases during the same period (Fig. 1) [6]. The healthcare costs associated with CVD are correspondingly large; based on data collected between 1997 and 2001, productivity losses associated with smoking in the United States have been estimated at approximately $92 billion [7].
Worldwide, the number of smokers continues to increase and is estimated to reach 1.7 billion by 2025 (Fig. 2A) [8], [9]. An estimated 4.83 million people died prematurely due to smoking in 2000, with this figure projected to increase to 8 million per year globally by 2030 if current trends continue (Fig. 2B) [9]. In the 2006 National Health Interview Survey in the United States, the Centre for Disease Control and Prevention (CDC) [10] found the prevalence of current smoking among persons with a smoking-related chronic disease to be significantly higher (36.9%) than among those without a chronic disease (19.3%) and was highest among adults with emphysema (49.1%) and chronic bronchitis (41.1%). Similar observations have been made in clinical trials in patients with established CVD: for example, 21% of patients were current smokers in the Incremental Decrease in End Points Through Aggressive Lipid Lowering (IDEAL) study, [11] and 41% in the Aggrastat-to-Zocor (A-to-Z) trial [12].
Current data on smoking as a CVD risk factor and the role of smoking cessation in potentially reducing CVD risk and related morbidity and mortality are reviewed here. An overview of interventions – pharmacological and behavioral – for smoking cessation is provided. This review aims to emphasize the relevance of smoking cessation in the quest for improved CVD health and highlight that many healthcare professionals currently fail to intervene adequately in their patients’ smoking habits, thereby missing a significant opportunity to address the devastating problems caused by CVD. Changing smoking behavior, as part of broader lifestyle interventions, is a cornerstone of improved CVD health. Pharmacotherapies and behavioral interventions should be employed as widely as possible to achieve this goal.
Section snippets
Smoking—a major risk factor for CVD
Most of the risk of acute myocardial infarction (MI) associated with CVD can be explained by nine factors (the INTERHEART study), of which six increase the odds ratios (ORs) for MI and three decrease the ORs for MI (Table 2) [13]. Of these factors, smoking is second only to dyslipidemia as a risk factor for MI. According to the Systemic Coronary Risk Evaluation (SCORE) project, the 10-year fatal cardiovascular risk is approximately doubled for smokers vs. non-smokers for any given age, systolic
Pathophysiological changes induced by smoking
There are several potential mechanisms by which smoking may increase the risk of CVD, although the precise roles have yet to be established (Table 3).
Smoking cessation improves cardiovascular health
Many pathophysiological changes caused by smoking can be reversed or improved by smoking cessation. For example, a nicotine replacement therapy (NRT) trial established that hemorheology parameters such as plasma fibrinogen, reactive capillary flow, and transcutaneous partial oxygen tension were also significantly improved in abstainers and other CVD risk factors such as hematocrit and white blood cell count also decreased to a greater extent in abstainers than in relapsers [45]. Chronic smokers
Underuse of smoking cessation therapy by healthcare professionals
In spite of the known health risks of smoking and the desire of smokers to stop, quit rates are low. The CDC reported that in 2000, approximately 70% of smokers wanted to stop smoking. Although 40% made a quit attempt in the preceding year, approximately 95% of these relapsed within 1 year [54]. One reason for these low quit rates may be that smoking is considered a “lifestyle choice” rather than a medical condition that stems from nicotine addiction. Thus, although there currently exists a
Smoking cessation therapies: new inroads to treating the disease
Nicotine addiction should be viewed as a chronic, relapsing medical condition which, like other major CVD risk factors, requires treatment, close follow-up, and repeated assessment and intervention [64]. Although approved smoking cessation pharmacotherapies vary between countries, NRT and bupropion SR are generally available as first-line therapies and are the most widely used [64]. Varenicline is approved in many countries in Europe as well as elsewhere including Japan and China. It is also
CVD risk management requires lifestyle changes
The strong association between lifestyle and risk of CVD is well established. As a group, smokers have lifestyles that place them at greater risk for chronic CVD compared with non-smokers, including consuming diets higher in fat and lower in antioxidants [88]. The Coronary Artery Surgery Study (CASS), which followed patients for 10 years, found that in comparison to non-smokers, smokers were more likely to be unemployed, showed limited activity, more likely to suffer angina, and experience a
Recommendations for the clinician
A smoking cessation algorithm based on the 5As referred to in Section 5 has been widely reproduced in clinical guidelines [64] and should form the basis of any clinician's approach to addressing the smoking habits of their patients (Table 4). All healthcare facilities should use this algorithm as a basis for the development of their own protocol, to ensure all tobacco users in a healthcare setting are identified and treated, and that all health professionals who come into contact with a patient
Conclusions
The high incidence of CVD related to smoking warrants an urgent approach to the treatment of nicotine addiction, one that encompasses the specialist setting – including cardiology – as well as primary care. Smoking is one of the most significant factors contributing to the risk of MI and IHD [13], [18]. Despite its role in morbidity and mortality, the prevalence of smoking is increasing worldwide [8], [17]; therefore an important component of managing the global risk of CVD is treating nicotine
Disclosure
Dr. Erhardt has given lectures for, and been a consultant to, Pfizer, AstraZeneca, Merck Sharp & Dohme, and Speedel.
Editorial support was provided by Brenda Smith, Ph.D. and Aideen Young, Ph.D. of Envision Pharma and funded by Pfizer, Inc.
Acknowledgment
The author would like to thank Majid Ezzati, Ph.D. for data on the number of smoking-attributable CVD deaths.
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