Smoking

Defining CMR - Epidemiology - Traditional Modifiable CVD Risk Factors

Key Points

  • Cigarette smoking is a major preventable risk factor that must be targeted as part of CVD prevention and management.
  • Cigarette smokers are 2 to 4 times more likely to develop CHD than non-smokers.
  • There is a significant dose response relationship between the number of cigarettes smoked and the relative risk of CHD and stroke.
  • When compared to non-obese smokers, obese smokers have a clear reduction in life expectancy.
  • Passive smoking and exposure to environmental smoke significantly increase the relative risk of CHD and stroke.
  • Quitting smoking has been shown to have a definite, positive impact on overall health.

Smoking: a Dangerous Addiction

Cardiovascular disease (CVD) is a multifactorial disease. For it to be managed effectively, all risk factors must be taken into account, including smoking. Cigarette smoke contains some 4,000 compounds, including carbon monoxide, ammonia, and known carcinogens [1], and the nicotine in cigarettes is highly addictive. Cigarette smoking is not only linked to various cancers (lung, esophagus, bladder, kidney, stomach, pancreas, etc.) and pulmonary diseases, it also significantly increases the risk of coronary heart disease (CHD), stroke, and peripheral vascular disease. Given its ties to so many health problems, cigarette smoking is a major modifiable risk factor that should be targeted aggressively as part of CVD prevention and management.

Some Statistics

On a global scale, smoking-related mortality is set to rise from 3 million annually (1995 estimate) to 10 million annually by 2030, with 70% of these deaths occurring in developing countries [2]. Smoking prevalence in men is currently highest in Pacific region countries, such as South Korea (68%), China (61%), and Japan (59%).

Among Americans aged 18 and older, 23.4% of men (25.1 million) and 18.5% of women (20.9 millions) are smokers, which puts them at increased risk of CHD [3]. From 1997-2001, approximately 437,902 Americans died each year of smoking-related illnesses, and 34.7% of these deaths were related to cardiovascular complications [4]. On average, male smokers die 13.2 years earlier than male non-smokers, whereas female smokers die 14.5 years earlier than non-smoking women [3]. Moreover, it has been estimated that 35,052 non-smokers die from CHD each year in the United States as a result of exposure to environmental tobacco smoke [4].

Smoking and Cardiovascular Health

It is well established that cigarette smoking is one of the most important modifiable risk factors for CHD [3,5-14]. The Centers for Disease Control and Prevention have reported that cigarette smokers are 2 to 4 times more likely to develop CHD than non-smokers [3]. Smokers are also more than 10 times more likely to develop peripheral vascular disease than non-smokers. It has been estimated that cigarette smoking approximately doubles a person’s risk for stroke. The pooled relative risk of stroke associated with cigarette smoking was 1.5 in a meta-analysis conducted by Shinton et al. [9]. In addition, the Atherosclerosis Risk in Communities (ARIC) Study showed that smoking-related CHD risk was much higher in the presence of higher LDL cholesterol [15]. In the INTERHEART study, a myocardial infarction case-control study conducted in 52 countries, current smokers had a greater risk (odds ratio [OR]: 2.95) of acute myocardial infarction (AMI) compared to individuals who had never smoked. By shortening life, smoking decreases CVD probability and duration throughout the life course, though non-smokers live many years longer and are longer free of CVD than smokers [16]. The risk associated with cigarette smoking varies with age, sex, ethnicity, amount of cigarettes smoked per day, and other factors.

Effect of Age
CVD risk was higher among smokers before age 70 in Framingham Heart Study participants [16]. The relative risk of stroke associated with smoking is present at all ages but is far greater in younger people [9,17]. In fact, it was found to be 2.9 in individuals under 55 years of age, 1.8 for those 55-74 years old, and 1.8 after 75 years of age [9]. In the INTERHEART cohort, the effect of smoking was much greater in younger (OR for AMI of 5.60) than in older individuals (OR of 3.60), especially in heavy smokers (more than 20 cigarettes per day) [18].

Effect of Sex
In Framingham cohort participants, the CVD risk associated with smoking ranged from 1.39 to 1.65 in women and men, respectively [16]. In the meta-analysis by Shinton et al. [9], the pooled relative risks of stroke in men and women were 1.72 and 1.43, respectively. However, other studies have also reported an increased relative risk of CHD from smoking in women when compared to men [9,17,19-21]. This inconsistency could be due to the fact that women have a higher dose per unit of body mass from a single cigarette.

Effect of Ethnicity
In addition, smoking has been suggested to be more harmful to Whites than to Hispanics and Blacks [22]. In the Asia-Pacific region, cigarette smoking has been shown to be a risk factor for both CHD and stroke, independent of body mass index (BMI), blood pressure, and cholesterol [17]. In this population, the relative risk was 1.6 for CHD, 1.19 for hemorrhagic stroke, and 1.38 for ischemic stroke.

Effect of Number of Cigarettes Smoked
There is a clear dose response between the number of cigarettes smoked and relative risk of CHD and stroke [9,17]. The pooled relative risk of stroke ranged from 1.37 in light smokers to 1.82 in heavy smokers [9]. In the INTERHEART cohort, AMI risks were also tied to the number of cigarettes smoked, with light smokers (1-9 cigarettes per day) having an OR of 1.63, moderate smokers (10-19 cigarettes per day) having an OR of 2.59, and heavy smokers (20 or more cigarettes per day) having an OR of 4.59 [18]. This clear dose response between the number of cigarettes smoked and AMI risk was observed in both men and women, with a 5 to 6% increase in risk for every additional cigarette smoked [18]. In women in the Asia-Pacific region, the hazard ratios for both CHD and stroke were found to be much higher than in men for the same amount of cigarettes smoked [17].

Effect of Passive Smoking and Environmental Smoke
Numerous epidemiological studies and reviews have studied the effect of passive smoking on CHD risk. A meta-analysis by He et al. [23] reported that passive smoking along with exposure to environmental smoke in non-smoking individuals increases CHD risk. In non-smokers exposed to environmental smoke, the relative risk of CHD was 1.25 and a dose response was clearly observed, with relative risks of 1.23 and 1.31, respectively, for non-smokers who were exposed to the smoke of 1-19 cigarettes per day and those who were exposed to the smoke of 20 or more cigarettes per day. In the INTERHEART study, AMI risk attributable to tobacco smoke exposure for more than 1 hour per week in never smokers was 15.4% [18].

Smoking and Obesity

When compared to non-obese smokers, obese smokers have a clear reduction in life expectancy [24,25]. Obesity induces several inflammatory markers and cytokines that might contribute to cardiovascular risk. Cigarette smoking, especially in chronic smokers, has also been linked to the induction of several cytokines, such as intracellular adhesion molecule-1 (ICAM-1), tumor necrosis- α (TNF-α), and oxidative stress molecules, while decreasing adiponectin concentrations, inducing insulin resistance, and promoting endothelial dysfunction, which is an early marker of atherosclerosis [26]. Furthermore, smoking has also been linked to insulin resistance and low HDL cholesterol levels [27]. The figure shows the additional effects of smoking in obese individuals.

In addition to being a risk factor for arteriosclerosis and ischemic stroke, smoking also increases visceral adipose tissue such that smokers have more of this harmful type of fat compared to non-smokers, even after adjusting for markers of total adiposity [28,29]. These results strongly suggest that body fat distribution can be modified by behavioural factors such as cigarette smoking, despite a well-documented genetic susceptibility to visceral adiposity [30]. This finding is especially important given that visceral obesity has been reported to be closely associated with the features of the metabolic syndrome increasing the risk of CVD and type 2 diabetes [31].

Smoking Cessation

The only way to decrease a smoker’s CVD risk and eliminate this major CVD risk burden is complete smoking cessation. Each cigarette temporarily increases heart rate and blood pressure, and smoking just a few cigarettes per day has been shown to be harmful to cardiovascular health. Because smoking duration is linked to smoking-related morbidity, early cessation and prevention of relapse are both important objectives.

In the meta-analysis by Shinton et al. [9], ex-smokers under the age of 75 seemed to retain an appreciably increased risk of stroke (1.5), but for all ages, the relative risk in ex-smokers was found to be 1.2. In a systematic review by Critchley et al. [32], quitting smoking was associated with a 36% (relative risk of 0.64) reduction in relative risk of mortality in patients with CHD who quit smoking when compared to those who continued smoking, regardless of age and sex. In Asia, the smoking epidemic’s impact is enormous, and quitting has been shown to provide a clear benefit. In this region, the hazard ratios for ex-smokers was 0.71 for CHD and 0.84 for stroke [17]. In the INTERHEART study, the OR associated with smoking fell to 1.87 (current smoking with an OR of 2.95) within 3 years of quitting. However, in people who had quit smoking 20 or more years ago, there was a residual excess risk of AMI of about 22% [18]. Even though quitting smoking provides clear overall health benefits, the speed and degree of mortality risk reduction associated with quitting is still being debated in the literature.

Several cessation programs/guidelines are available to smokers and health care professionals. In order to improve smoking cessation rates, effective behavioural and pharmacological treatments, coupled with professional counselling and advice, are required. Since smoking duration is the principal risk factor for smoking-related morbidity, cessation and prevention of relapse are both key goals.

The association between cigarette smoking and CVD is overwhelmingly clear. As a result, clinicians must emphasize to their patients the importance of quitting smoking to reduce their relative CVD risk. Also requiring special attention are the harmful effects of passive smoking and environmental smoke exposure with regard to CHD. Many of the adverse health effects caused by smoking are reversible, and smoking cessation treatments are among the most cost-effective healthcare interventions. Although quitting smoking at a younger age confers the greatest benefit, even those who quit in middle-age can avoid much of the excess healthcare risk associated with smoking.

References

  1. Smith CJ, Livingston SD and Doolittle DJ. An international literature survey of “IARC Group I carcinogens” reported in mainstream cigarette smoke. Food Chem Toxicol 1997; 35: 1107-30.

    PubMed ID: 9463546
  2. Fagerstrom K. The epidemiology of smoking: health consequences and benefits of cessation. Drugs 2002; 62 Suppl 2: 1-9.

    PubMed ID: 12109931
  3. Rosamond W, Flegal K, Friday G, et al. Heart disease and stroke statistics–2007 update: a report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation 2007; 115: e69-171.

    PubMed ID: 17194875
  4. Annual smoking-attributable mortality, years of potential life lost, and productivity losses–United States, 1997-2001. MMWR Morb Mortal Wkly Rep 2005; 54: 625-8.

    PubMed ID: 15988406
  5. Wolf PA, D’Agostino RB, Belanger AJ, et al. Probability of stroke: a risk profile from the Framingham Study. Stroke 1991; 22: 312-8.

    PubMed ID: 2003301
  6. Bonita R, Scragg R, Stewart A, et al. Cigarette smoking and risk of premature stroke in men and women. BMJ 1986; 293: 6-8.

    PubMed ID: 3089404
  7. Abbott RD, Yin Y, Reed DM, et al. Risk of stroke in male cigarette smokers. N Engl J Med 1986; 315: 717-20.

    PubMed ID: 3748080
  8. Colditz GA, Bonita R, Stampfer MJ, et al. Cigarette smoking and risk of stroke in middle-aged women. N Engl J Med 1988; 318: 937-41.

    PubMed ID: 3352685
  9. Shinton R and Beevers G. Meta-analysis of relation between cigarette smoking and stroke. BMJ 1989; 298: 789-94.

    PubMed ID: 2496858
  10. Haapanen A, Koskenvuo M, Kaprio J, et al. Carotid arteriosclerosis in identical twins discordant for cigarette smoking. Circulation 1989; 80: 10-6.

    PubMed ID: 2661052
  11. Whisnant JP, Homer D, Ingall TJ, et al. Duration of cigarette smoking is the strongest predictor of severe extracranial carotid artery atherosclerosis. Stroke 1990; 21: 707-14.

    PubMed ID: 2339450
  12. Howard G, Burke GL, Szklo M, et al. Active and passive smoking are associated with increased carotid wall thickness. The Atherosclerosis Risk in Communities Study. Arch Intern Med 1994; 154: 1277-82.

    PubMed ID: 8203995
  13. Doll R, Peto R, Wheatley K, et al. Mortality in relation to smoking: 40 years’ observations on male British doctors. BMJ 1994; 309: 901-11.

    PubMed ID: 7755693
  14. Ockene IS and Miller NH. Cigarette smoking, cardiovascular disease, and stroke: a statement for healthcare professionals from the American Heart Association. American Heart Association Task Force on Risk Reduction. Circulation 1997; 96: 3243-7.

    PubMed ID: 9386200
  15. Hozawa A, Folsom AR, Sharrett AR, et al. Does the impact of smoking on coronary heart disease differ by low-density lipoprotein cholesterol level? the Atherosclerosis Risk in Communities (ARIC) Study. Circ J 2006; 70: 1105-10.

    PubMed ID: 16936419
  16. Mamun AA, Peeters A, Barendregt J, et al. Smoking decreases the duration of life lived with and without cardiovascular disease: a life course analysis of the Framingham Heart Study. Eur Heart J 2004; 25: 409-15.

    PubMed ID: 15033253
  17. Woodward M, Lam TH, Barzi F, et al. Smoking, quitting, and the risk of cardiovascular disease among women and men in the Asia-Pacific region. Int J Epidemiol 2005; 34: 1036-45.

    PubMed ID: 15914503
  18. Teo KK, Ounpuu S, Hawken S, et al. Tobacco use and risk of myocardial infarction in 52 countries in the INTERHEART study: a case-control study. Lancet 2006; 368: 647-58.

    PubMed ID: 16920470
  19. Njolstad I, Arnesen E and Lund-Larsen PG. Smoking, serum lipids, blood pressure, and sex differences in myocardial infarction. A 12-year follow-up of the Finnmark Study. Circulation 1996; 93: 450-6.

    PubMed ID: 8565161
  20. Prescott E, Hippe M, Schnohr P, et al. Smoking and risk of myocardial infarction in women and men: longitudinal population study. BMJ 1998; 316: 1043-7.

    PubMed ID: 9552903
  21. He Y and Lam TH. A review on studies of smoking and coronary heart disease in China and Hong Kong. Chin Med J (Engl) 1999; 112: 3-8.

    PubMed ID: 11593636
  22. Mast H, Thompson JL, Lin IF, et al. Cigarette smoking as a determinant of high-grade carotid artery stenosis in Hispanic, black, and white patients with stroke or transient ischemic attack. Stroke 1998; 29: 908-12.

    PubMed ID: 9596233
  23. He J, Vupputuri S, Allen K, et al. Passive smoking and the risk of coronary heart disease–a meta-analysis of epidemiologic studies. N Engl J Med 1999; 340: 920-6.

    PubMed ID: 10089185
  24. Peeters A, Barendregt JJ, Willekens F, et al. Obesity in adulthood and its consequences for life expectancy: a life-table analysis. Ann Intern Med 2003; 138: 24-32.

    PubMed ID: 12513041
  25. Stevens J, Cai J, Evenson KR, et al. Fitness and fatness as predictors of mortality from all causes and from cardiovascular disease in men and women in the lipid research clinics study. Am J Epidemiol 2002; 156: 832-41.

    PubMed ID: 12397001
  26. Van Gaal LF, Mertens IL and De Block CE. Mechanisms linking obesity with cardiovascular disease. Nature 2006; 444: 875-80.

    PubMed ID: 17167476
  27. Reaven G and Tsao PS. Insulin resistance and compensatory hyperinsulinemia: the key player between cigarette smoking and cardiovascular disease? J Am Coll Cardiol 2003; 41: 1044-7.

    PubMed ID: 12651055
  28. Barrett-Connor E and Khaw KT. Cigarette smoking and increased central adiposity. Ann Intern Med 1989; 111: 783-7.

    PubMed ID: 2817625
  29. Shimokata H, Muller DC and Andres R. Studies in the distribution of body fat. III. Effects of cigarette smoking. JAMA 1989; 261: 1169-73.

    PubMed ID: 2915440
  30. Bouchard C, Tremblay A, Després JP, et al. The response to long-term overfeeding in identical twins. N Engl J Med 1990; 322: 1477-82.

    PubMed ID: 2336074
  31. Després JP and Lemieux I. Abdominal obesity and metabolic syndrome. Nature 2006; 444: 881-7.

    PubMed ID: 17167477
  32. Critchley JA and Capewell S. Mortality risk reduction associated with smoking cessation in patients with coronary heart disease: a systematic review. JAMA 2003; 290: 86-97.

    PubMed ID: 12837716
Reference 1 CLOSECLOSE

Smith CJ, Livingston SD and Doolittle DJ. An international literature survey of “IARC Group I carcinogens” reported in mainstream cigarette smoke. Food Chem Toxicol 1997; 35: 1107-30.

PubMed ID: 9463546
Reference 2 CLOSECLOSE

Fagerstrom K. The epidemiology of smoking: health consequences and benefits of cessation. Drugs 2002; 62 Suppl 2: 1-9.

PubMed ID: 12109931
Reference 3 CLOSECLOSE

Rosamond W, Flegal K, Friday G, et al. Heart disease and stroke statistics–2007 update: a report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation 2007; 115: e69-171.

PubMed ID: 17194875
Reference 4 CLOSECLOSE

Annual smoking-attributable mortality, years of potential life lost, and productivity losses–United States, 1997-2001. MMWR Morb Mortal Wkly Rep 2005; 54: 625-8.

PubMed ID: 15988406
Reference 5 CLOSECLOSE

Wolf PA, D’Agostino RB, Belanger AJ, et al. Probability of stroke: a risk profile from the Framingham Study. Stroke 1991; 22: 312-8.

PubMed ID: 2003301
Reference 6 CLOSECLOSE

Bonita R, Scragg R, Stewart A, et al. Cigarette smoking and risk of premature stroke in men and women. BMJ 1986; 293: 6-8.

PubMed ID: 3089404
Reference 7 CLOSECLOSE

Abbott RD, Yin Y, Reed DM, et al. Risk of stroke in male cigarette smokers. N Engl J Med 1986; 315: 717-20.

PubMed ID: 3748080
Reference 8 CLOSECLOSE

Colditz GA, Bonita R, Stampfer MJ, et al. Cigarette smoking and risk of stroke in middle-aged women. N Engl J Med 1988; 318: 937-41.

PubMed ID: 3352685
Reference 9 CLOSECLOSE

Shinton R and Beevers G. Meta-analysis of relation between cigarette smoking and stroke. BMJ 1989; 298: 789-94.

PubMed ID: 2496858
Reference 10 CLOSECLOSE

Haapanen A, Koskenvuo M, Kaprio J, et al. Carotid arteriosclerosis in identical twins discordant for cigarette smoking. Circulation 1989; 80: 10-6.

PubMed ID: 2661052
Reference 11 CLOSECLOSE

Whisnant JP, Homer D, Ingall TJ, et al. Duration of cigarette smoking is the strongest predictor of severe extracranial carotid artery atherosclerosis. Stroke 1990; 21: 707-14.

PubMed ID: 2339450
Reference 12 CLOSECLOSE

Howard G, Burke GL, Szklo M, et al. Active and passive smoking are associated with increased carotid wall thickness. The Atherosclerosis Risk in Communities Study. Arch Intern Med 1994; 154: 1277-82.

PubMed ID: 8203995
Reference 13 CLOSECLOSE

Doll R, Peto R, Wheatley K, et al. Mortality in relation to smoking: 40 years’ observations on male British doctors. BMJ 1994; 309: 901-11.

PubMed ID: 7755693
Reference 14 CLOSECLOSE

Ockene IS and Miller NH. Cigarette smoking, cardiovascular disease, and stroke: a statement for healthcare professionals from the American Heart Association. American Heart Association Task Force on Risk Reduction. Circulation 1997; 96: 3243-7.

PubMed ID: 9386200
Reference 15 CLOSECLOSE

Hozawa A, Folsom AR, Sharrett AR, et al. Does the impact of smoking on coronary heart disease differ by low-density lipoprotein cholesterol level? the Atherosclerosis Risk in Communities (ARIC) Study. Circ J 2006; 70: 1105-10.

PubMed ID: 16936419
Reference 16 CLOSECLOSE

Mamun AA, Peeters A, Barendregt J, et al. Smoking decreases the duration of life lived with and without cardiovascular disease: a life course analysis of the Framingham Heart Study. Eur Heart J 2004; 25: 409-15.

PubMed ID: 15033253
Reference 17 CLOSECLOSE

Woodward M, Lam TH, Barzi F, et al. Smoking, quitting, and the risk of cardiovascular disease among women and men in the Asia-Pacific region. Int J Epidemiol 2005; 34: 1036-45.

PubMed ID: 15914503
Reference 18 CLOSECLOSE

Teo KK, Ounpuu S, Hawken S, et al. Tobacco use and risk of myocardial infarction in 52 countries in the INTERHEART study: a case-control study. Lancet 2006; 368: 647-58.

PubMed ID: 16920470
Reference 19 CLOSECLOSE

Njolstad I, Arnesen E and Lund-Larsen PG. Smoking, serum lipids, blood pressure, and sex differences in myocardial infarction. A 12-year follow-up of the Finnmark Study. Circulation 1996; 93: 450-6.

PubMed ID: 8565161
Reference 20 CLOSECLOSE

Prescott E, Hippe M, Schnohr P, et al. Smoking and risk of myocardial infarction in women and men: longitudinal population study. BMJ 1998; 316: 1043-7.

PubMed ID: 9552903
Reference 21 CLOSECLOSE

He Y and Lam TH. A review on studies of smoking and coronary heart disease in China and Hong Kong. Chin Med J (Engl) 1999; 112: 3-8.

PubMed ID: 11593636
Reference 22 CLOSECLOSE

Mast H, Thompson JL, Lin IF, et al. Cigarette smoking as a determinant of high-grade carotid artery stenosis in Hispanic, black, and white patients with stroke or transient ischemic attack. Stroke 1998; 29: 908-12.

PubMed ID: 9596233
Reference 23 CLOSECLOSE

He J, Vupputuri S, Allen K, et al. Passive smoking and the risk of coronary heart disease–a meta-analysis of epidemiologic studies. N Engl J Med 1999; 340: 920-6.

PubMed ID: 10089185
Reference 24 CLOSECLOSE

Peeters A, Barendregt JJ, Willekens F, et al. Obesity in adulthood and its consequences for life expectancy: a life-table analysis. Ann Intern Med 2003; 138: 24-32.

PubMed ID: 12513041
Reference 25 CLOSECLOSE

Stevens J, Cai J, Evenson KR, et al. Fitness and fatness as predictors of mortality from all causes and from cardiovascular disease in men and women in the lipid research clinics study. Am J Epidemiol 2002; 156: 832-41.

PubMed ID: 12397001
Reference 26 CLOSECLOSE

Van Gaal LF, Mertens IL and De Block CE. Mechanisms linking obesity with cardiovascular disease. Nature 2006; 444: 875-80.

PubMed ID: 17167476
Reference 27 CLOSECLOSE

Reaven G and Tsao PS. Insulin resistance and compensatory hyperinsulinemia: the key player between cigarette smoking and cardiovascular disease? J Am Coll Cardiol 2003; 41: 1044-7.

PubMed ID: 12651055
Reference 28 CLOSECLOSE

Barrett-Connor E and Khaw KT. Cigarette smoking and increased central adiposity. Ann Intern Med 1989; 111: 783-7.

PubMed ID: 2817625
Reference 29 CLOSECLOSE

Shimokata H, Muller DC and Andres R. Studies in the distribution of body fat. III. Effects of cigarette smoking. JAMA 1989; 261: 1169-73.

PubMed ID: 2915440
Reference 30 CLOSECLOSE

Bouchard C, Tremblay A, Després JP, et al. The response to long-term overfeeding in identical twins. N Engl J Med 1990; 322: 1477-82.

PubMed ID: 2336074
Reference 31 CLOSECLOSE

Després JP and Lemieux I. Abdominal obesity and metabolic syndrome. Nature 2006; 444: 881-7.

PubMed ID: 17167477
Reference 32 CLOSECLOSE

Critchley JA and Capewell S. Mortality risk reduction associated with smoking cessation in patients with coronary heart disease: a systematic review. JAMA 2003; 290: 86-97.

PubMed ID: 12837716