There is no single, generally accepted definition for heavy smoking. A study reported in the September 2013 issue of the “International Journal of Environmental Research and Public Health” defined heavy smoking as 20 or more cigarettes per day, or 20 or more pack-years. A pack-year is determined by multiplying the number of cigarettes smoked per day by the number of years of smoking. Twenty pack-years is equivalent to a pack a day for 20 years, or 2 packs a day for 10 years. Other common cut-points for heavy smoking include 15 and 25 cigarettes per day.
Heavy Smoking and Lung Cancer
Smoking dramatically increases the risk for lung cancer. The more and longer you smoke, the greater the risk. Lung cancer is the leading cause of cancer deaths in the United States. According to the American Cancer Society, the 5-year survival rate is just 16 percent. Lung cancer is most common in heavy smokers age 55 and older. The U.S. Preventative Services Task Force recommends lung cancer screening for adults age 55 to 80 with a 30 pack-year history who currently smoke or have quit within the past 15 years.
More Cigarettes Escalate Risks
In a study published in the July 2005 issue of "Tobacco Control," the risk for lung cancer rose dramatically as the number of cigarettes increased. Women who smoked 1 to 4 cigarettes per day had a 5-times higher risk of lung cancer than non-smokers. The risk escalated from there, rising to more than a 30-fold increase for women who smoked 25 or more cigarettes daily. Men experienced nearly a 3-fold increase at 1 to 4 cigarettes, and the risk rose to more than 35-times that of non-smokers when 25 or more cigarettes were smoked daily.
Smoking and Heart Disease
Smoking is also a major risk factor for coronary heart disease, the leading cause of death in America. The July 2005 study in "Tobacco Control" found that the steepest increase in risk for heart disease occurred with just 1 to 4 cigarettes daily. Those who smoked 1 to 4 cigarettes per day -- both men and women -- experienced nearly a 3-fold increase in risk for heart disease compared to non-smokers. At 25 or more cigarettes per day, the risk was only slightly higher at approximately 3.5 times that of non-smokers.
No Safe Level
The 2010 report of the Surgeon General, "How Tobacco Smoke Causes Disease," concluded that there is no safe level of smoking. Cigarette smoke contains thousands of chemicals, many of which are known to cause cancer, cardiovascular and pulmonary disease. The report further concluded that even low levels of exposure, including secondhand exposure, cause sharp and rapid damage to the blood vessels. Smoking cessation and avoiding secondhand smoke is the only way to avoid the increased health risks associated with smoking.