Tobacco Consumption and Coronary Artery Disease
In the last article we discussed about hypertension as a risk factor for heart disease. Let’s see how smoking and tobacco consumption is another important risk factor for coronary artery disease. India is the 2nd largest country in the world in terms of consumption of tobacco after China. Longitudinal studies have shown that smoking is an important risk factor in the development of heart disease.
In 2000, there were an estimated 4.8 million premature deaths in the world attributable to smoking – 2.4 million in developing countries and 2 million in industrialised countries. More than three quarter (3.8 million) of these deaths were in men. The leading causes of death from smoking were cardiovascular (1.7 million deaths)
Smokers die 5 to 8 years earlier than non smokers. They have twice the risk of fatal heart disease. It is highly addictive, raises brain level of dopamine and produces withdrawal symptoms on discontinuation suddenly.
The mechanism by which tobacco consumption causes heart disease has been the subject of intense investigations. Nicotine is the major constituent of tobacco and has effect on lipids and sympathetic nervous system. Coronary blood flow may decrease after smoking, an effect possibly related to nicotine mediated increases in coronary vascular resistance. Circulating free fatty acids, glycerol and lactate concentration increases after smoking. Nicotine increases circulating level of vasopressin, growth hormone, cortisol, ACTH and endorphins.
Smokers have increased bad cholesterol (LDL) and reduced good cholesterol (HDL). These deranged fats lead to heart disease. It should be remembered that nicotine is only one of some 4,000 constituents that have been described in cigarette smoke.
The gaseous phase contains among others carbon monoxide, carbon dioxide, nitrogen dioxide and ammonia. These particles have active teratogenic and mutagenic constituents such as nicotine, phenol, phytosteroids and naphthalene.
Cigarette smoking is the most important risk factor for coronary artery spasm and vasospastic angina. The sympathomimetic action of nicotine together with its inability to produce prostacyclin suggests that nicotine causes the risk. Sudden cardiac death in smokers might result from ischemia combined with arrthymia affect of increasing circulating catecholamines.
Smoking cessation reduces the risk of death and myocardial infarction in people with heart disease. On average, women smokers who quitted smoking by age 35 add about three years to their life expectancy and men add more than two years. Factors associated with successful cessation include having a rule against smoking in the home, being older and having greater education. Several effective interventions are available to promote smoking cessation including, counselling, pharmacotherapy and combination of the two.
The cardiovascular benefits of stopping smoking have been well documented and are listed below.
- Within 1 to 2 years after quitting the risk of MI (myocardial infarction) falls by 30 percent in men and 40 percent in women.
- The risk of MI in former smokers approaches that of never smokers within 2 to 4 years after cessation.
- Quitting after a MI adds 1.7 years of life compared to persons who continue to smoke.
- 35 years old men and women who quit add 2.3 and 2.8 years of life respectively to their life expectancy.
- Five years mortality in smokers is double that of those who quit.
- Risk of stroke is reduced within 2 years after cessation and diminishes to that of never smokers after 5 years.
- The risk of dying from lung cancer decreases by 40 percent in 6 to 10 years but, even after 15 years the risk is still 10 to 20 percent higher than never smokers.
- While the overall mortality rate declines rapidly in former smokers, it never returns to the baseline of never smokers.
- Other benefits: Reduction of symptoms from peripheral vascular disease, reduction in aortic aneurysm mortality, reduced peptic ulcer disease, improved blood pressure control, improved lipid profile and better pregnancy outcomes.
- There is on an average of 6.4 lb weight gain following smoking cessation but the health risks of this weight gain are negligible compared to the benefits of cessation.
Dr Narottam Bhardwaj completed MBBS in 1973 and MD in Medicine in 1978 from Maulana Azad Medical College, University of Delhi. He worked for three years in LNJP and GB Pant Hospitals, New Delhi from 1982. He has been in private practice as a consultant physician to various hospitals like Indraprastha Apollo Hospital, etc. At present he is senior consultant- Internal Medicine at Max Hospital, Saket, Sukhda Hospital, New Delhi. He is also Medical Advisor to Power Grid Corporation, Power Finance Corporation and SIEMENS. He has published several papers on diabetes, hypertension and heart disease. He has special interest in diabetes. He is a member of Delhi Medical Association and American Diabetic Association.