The link between smoking and heart disease has been well described in populations all over the world. Twenty five year follow up of the Seven Countries Study, (16 cohorts of men aged 40 to 59 at enrolment in the USA, Finland, the Netherlands, Italy, Croatia, Serbia, Greece and Japan), reported a dose-dependent increase in risk of death. After 25 years, 57.7% of persons smoking 30 cigarettes per day had died, compared to only 36.3% of non-smokers1. Additional long-term data come from a 40 year follow up of British physicians which noted that excess mortality from cardiovascular disease was two times higher among smokers compared to non-smokers but that this ratio was even more extreme during middle age 2.
The data for men and women differ somewhat but recent work underlines the importance of smoking as a cause of myocardial infarction in both men and women. As an example, in a Norwegian study, rates of myocardial infarction were 4.6 times higher in men than in women but rates among women who smoked were six times higher than non-smokers and rates among men, three times higher than among nonsmokers 3. Danish investigators concluded that women may be more sensitive to tobacco as risks of myocardial infarction due to both current smoking and total tobacco exposure were consistently higher in women than men, and higher for both groups than myocardial infarction rates among non-smokers 4.
A myocardial infarction happens in part due to decreased blood flow to the heart muscle itself. This decrease occurs typically when a vessel, narrowed, (or stenosed) due to atherosclerosis as plaques of lipid (fatty) material build up in blood vessels, is blocked by a blood clot or a breakup of the plaque material. Other blood vessels, particularly the carotid arteries to the brain and small vessels in the legs, can also be affected and produce disease, either stroke in the case of the carotid stenosis, or peripheral vascular disease in the case of blood vessels in the leg.
While there are certain genetic conditions that cause atherosclerosis, studies of twin pairs in which one smokes and the other does not demonstrate that smoking can increase the size of plaques in the carotid arteries by over threefold 5. A larger plaque means the vessel is more narrow, thus increasing risk of stroke, in the case of the carotid arteries, or ischemic heart disease in the case of coronary arteries.
In an increasing number of health systems, patients are offered expensive therapies such as coronary bypass surgery or angioplasty in an effort to open or bypass vessels that have become so narrow that they are unable to supply sufficient oxygen to the heart. American data report that after an average four and a half years of followup, people who continued to smoke after angioplasty had a 76% increased risk of death compared to nonsmokers and a 44% higher risk of death compared to those who quit smoking6. Even stronger evidence comes from a 15 year follow up of Dutch patients who underwent bypass surgery. People smoking one year after surgery had a risk of subsequent myocardial infraction over two times higher than those who had quit smoking.
Moreover, risks of myocardial infarction were similar among non-smokers and those who were successful in quitting after surgery 7.
(2) Doll R, Peto R, Wheatley K, et al. Mortality in relation to smoking: 40 years? observations on male British doctors. BMJ 1994; 309: 901-911.
(3) Njolstad I, Arnesen E, Lund-Larsen PG. Smoking, serum lipids, blood pressure, and sex differences in myocardial infarction. Circulation 1996; 93:450-456.
(4) Prescott E. Hippe M, Schnohr P, et al. Smoking and risk of myocardial infarction in women and men: longitudinal population study. BMJ 1998: 316:1043-47.
(5) Haapanen A, Koskenvuo M, Kaprio J, Kesaniemi YA, Heikkila K. Carotid arteriosclerosis in identical twins discordant for cigarette smoking. Circulation 1989; 80: 10-16.
(6) Hasdai D, Garratt KN, Grill DE, et al. Effect of smoking status on the long-term outcome after successful percutaneous coronary revascularization. The New England Journal of Medicine1997; 336: 755-61.
(7) Voors AA, van Brussel BL, Plokker T, et al. Smoking and cardiac events after venous coronary bypass surgery. Circulation 1996; 93:42-47.