Over the years, epidemiological studies have associated smoking with many different serious and fatal diseases. The diseases most studied have been lung cancer, chronic obstructive pulmonary disease, and coronary heart disease, mainly because these are major causes of death in many countries.
Studies consistently report such strong associations between smoking and lung cancer that it is reasonable to conclude that smoking is a significant cause of lung cancer. The statistics report higher incidence of lung cancer in groups that smoke for more years and smoke more cigarettes per day, with the length of time people have been smoking thought to be the most important factor. Health Canada states that smoking accounts for 85% of all new cases of lung cancer in Canada. After quitting, risks begin to decline and will vary according to a person’s smoking history. Health Canada indicates that a former smoker’s level of risk of lung cancer is cut in half after about 10 years or so of abstinence.
Chronic obstructive pulmonary disease (COPD)
COPD includes chronic bronchitis and emphysema. Studies consistently report relationships between smoking and COPD that are of similar magnitude to the risks identified between smoking and lung cancer. As with lung cancer, the incidence is highest in groups that smoke for longer and smoke more cigarettes per day. Quitting is thought to slow the progression of the disease. Risks in groups of ex-smokers tend to remain higher than for non-smokers, but lower than for those who continue to smoke.
Coronary heart disease (CHD)
Smoking is one of the causes of coronary heart disease. Heart disease is linked with many other factors, such as high cholesterol, high blood pressure, obesity, and lack of exercise. Some studies have reported that the risks of heart disease are greater in groups of people that have more than one of these risk factors (for example, smokers who exercise infrequently). Health Canada states that within one year of quitting the risk of smoking-related heart attack is cut in half and that within 15 years of abstinence the risk of dying from a heart attack is equal to a person who has never smoked.
Smoking during pregnancy
Public health authorities advise that pregnant women should not smoke under any circumstances, and have widely publicized this warning. Many statistical studies have reported a link between lower birth weight in babies of mothers who smoke throughout pregnancy. Some studies have reported, among other factors, links between smoking during pregnancy and infant mortality, premature birth, miscarriage, and stillbirth.
What people should consider about smoking
Smoking is a cause of various serious and fatal diseases. The health risks in groups vary by the amount smoked,and are highest in those people who smoke for more years and smoke more cigarettes per day. Please consult Health Canada’s website for more information on this topic.