What is the relationship between respiratory diseases and smoking?

Quick Answer
Chronic bronchitis, emphysema, chronic obstructive pulmonary disease, and lung cancer are caused by smoking tobacco in a majority of cases. The first three affect lung functioning to varying degrees, depending on how far the condition has progressed; lung cancer is one of the fastest-spreading and most deadly forms of cancer.
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Smoking tobacco is the primary cause of a number of respiratory diseases, the most serious being chronic bronchitis, emphysema, chronic obstructive pulmonary disease (COPD), and lung cancer. Most long-term smokers started as preteens or teenagers, became addicted to nicotine, and then subjected their respiratory systems to the toxins and carcinogens contained in the tobacco.

Tobacco smoke contains thousands of chemical compounds and more than four hundred toxic and carcinogenic substances. According to the American Lung Association in 2015, smoking-related respiratory diseases kill more than 480,000 people each year in the United States alone. Smoking causes about 90 percent of lung cancer cases and 85 to 90 percent of COPD cases. The Centers for Disease Control and Prevention reported in 2015 that lung cancer was the leading cause of cancer death and the second most common cancer among men and women in the United States. The CDC also reported in 2015 that chronic lower respiratory disease, mostly COPD, was the third leading cause of death in the United States in 2011.

Chronic bronchitis occurs when there is an increase in the size and number of mucous glands in the large airways of the lungs. The increased amount of mucus inflames and scars the airways, constricting air flow, which becomes more pronounced with continued scarring and thickening of the airway walls.

Emphysema results from damage to the lungs’ alveoli, or air sacs, which facilitate the exchange of carbon dioxide and oxygen. This condition further compromises breathing because of the constriction of airways from the loss of lung elasticity.

COPD is a condition that usually includes a combination of chronic bronchitis and emphysema, resulting in forced and inefficient breathing. The degree of the contribution of each component condition to COPD varies from case to case. Lung cancer occurs when carcinogens, most often from cigarette smoke, cause damage to lung cells, leading to abnormal cellular replication that creates tumors in the larger airways or other parts of the lung.

Risk Factors

Although people who have never smoked can potentially develop respiratory ailments from factors such as genetics or exposure to job-related or general air pollution, the cause of 80 to 90 percent of all serious respiratory diseases is long-term tobacco smoking. Researchers estimate that approximately fifteen hundred preteens and teenagers each day become addicted to nicotine, and many of them will become life-long smokers.

There is a positive linear correlation between the risk of major respiratory disease and the duration of exposure, which is measured in “package-years,” determined by years of smoking multiplied by the number of packs of cigarettes per day. This measurement places older chronic smokers at highest risk. Research shows that nonsmokers who are exposed to secondhand or passive smoke, because they live, work, or recreate in smoke-filled environments, are at a significantly increased risk of developing serious respiratory diseases.


Chronic bronchitis, often called smoker’s cough, is evidenced by the coughing up of sputum, or phlegm, for a minimum of three months during two or more consecutive years. Emphysema is characterized by severe shortness of breath that makes physical activity increasingly difficult as the disease progresses to the point of total disability. Common symptoms include exhaustion, coughing, heart problems, and enlarged chest because of labored breathing.

Indicators of COPD include all of the symptoms of chronic bronchitis and emphysema. As COPD progresses, respiratory inefficiency further increases carbon dioxide levels and reduces oxygen levels in the blood, which is evidenced by drowsiness, twitching, headaches, lips assuming a bluish pallor, severe shortness of breath, and swollen ankles from heart strain. Some symptoms associated with lung cancer are labored breathing, chest pain, hoarseness, phlegm containing blood, lack of strength in the hands or arms, and swollen face and neck.

Screening and Diagnosis

Because chronic bronchitis and emphysema are both obstructive pulmonary diseases that are typically combined in COPD (to some degree), the diagnostic tests for all three conditions are the same. In all three cases, patients are asked if they smoke or have ever smoked, or if they work with lung-damaging chemicals. A number of tests are then performed.

A spirometry test that shows that less than 70 percent of the air is expelled from the lungs during exhaling indicates COPD. X-rays and computed tomography (CT) scans can detect damage to lung tissue and increased air in the chest. Excessive air in the lungs can be determined with a lung volume test, which indicates COPD. Diffusing capacity and arterial blood gas tests measure how efficient the lungs are in eliminating carbon dioxide and supplying oxygen to the blood. A body plethysmography shows whether asthma is present in conjunction with emphysema, and an alpha-1 antitrypsin deficiency test can detect a relatively rare form of genetically inherited emphysema.

Lung cancer is diagnosed with X-rays or a CT scan to reveal the presence of tumors. If tumors are present, lung mucus or fluid is often examined for the presence of cancer cells. The definitive diagnosis usually involves the removal of a small sample of tissue from tumors with an instrument that is inserted through the air passage, on which a biopsy is performed to determine if the growths are cancerous.

Treatment and Therapy

Because chronic bronchitis, emphysema, and COPD are caused by smoking in a majority of cases, the first treatment strategy for patients who are active smokers is to quit. The body can repair lung damage in short-term smokers, and although the effects of advanced COPD are irreversible and progressive, smoking cessation can slow the rate of progression. While COPD is progressive and potentially fatal, management strategies can improve the patient’s quality of life and extend longevity.

Patients with low oxygen levels can take supplemental oxygen from an oxygen cylinder or concentrator through nasal tubes or an oxygen mask, which allows them to lead more active lives. Oxygen dosages must be carefully monitored to avoid a number of serious side effects. Being overweight or underweight can affect the progression and severity of symptoms of COPD, so adjustments in diet in combination with counseling and an exercise program can reduce the degree of infirmity.

A number of medications can help to control COPD symptoms. Nebulizers are used to administer anticholinerics or B2 agonists. Both are bronchodilators that act quickly to improve air flow by relaxing muscles around airways. In advanced COPD cases, corticosteroids are administered to reduce airway inflammation, but the side effects include a higher probability of pneumonia. In some of the most advanced COPD cases, the patient may need surgery to remove the most severely damaged parts of the lungs, or a lung transplant may need to be performed.

The treatment for lung cancer varies depending on the type of cancer and how far the disease has progressed. Non-small-cell lung cancer develops relatively slowly and, if diagnosed early, is treated with surgery that may involve removing the tumor, a portion of the lung, or the entire lung. Often, radiation therapy, which kills cancer cells with X-rays, follows the surgery. Chemotherapy, which kills cancer cells with powerful medications, is sometimes used in conjunction with surgery and radiation therapy.

Small-cell lung cancer progresses and spreads to other organs relatively quickly and is usually treated with radiation therapy or chemotherapy. All persons with cancer who also are smokers are strongly advised to quit smoking. Nicotine and the chemicals in cigarette smoke retard the healing process after surgery and appear to promote cancer cell growth while insulating cancer cells from the destructive effects of both radiation therapy and chemotherapy. After the initial treatment, cancer patients have ongoing follow-up care that includes X-rays and CT scans, blood work, and physical examinations to check for a possible recurrence of the disease.


Because 80 to 90 percent of all cases of chronic bronchitis, emphysema, COPD, and lung cancer are caused by smoking, the most important preventive measures are to not start smoking, to quit if one already smokes, and to avoid secondhand smoke. Management and workers in industries in which the work environment exposes personnel to dust and harmful chemicals should be aware of the importance of adequate ventilation; of using respirators; and of monitoring and controlling dust, toxin, and carcinogen levels.


American Lung Assn. “Smoking Facts.” Lung.org. ALA, 2015. Web. 30 Oct. 2015.

Centers for Disease Control and Prevention. “Chronic Obstructive Pulmonary Disease.” CDC.gov. CDC, 12 Mar. 2015. Web. 30 Oct. 2015.

Centers for Disease Control and Prevention. “Lung Cancer.” CDC.gov. CDC, 16 Sept. 2015. Web. 30 Oct. 2015.

Owing, J. H., ed. Smoking and Health: New Research. Hauppauge: Nova Science, 2005. Print.

Slovic, Paul, ed. Smoking: Risk, Perception, and Policy. Thousand Oaks: Sage, 2001. Print.

Ward, Jeremy P. T., Jane Ward, and Richard M. Leach. The Respiratory System at a Glance. Hoboken: Wiley, 2010. Print.