Chronic Obstructive Pulmonary Disease: Overview and Risk Factors
Chronic obstructive pulmonary disease (COPD) is a severe, irreversible disease of the lungs caused by smoking. COPD affects 14 million Americans and is the fourth most common cause of death in the United States. The rate of this disease is on the rise, due to increasing worldwide cigarette use and air pollution.
COPD comprises two entities: chronic bronchitis and emphysema.
Chronic bronchitis is characterized by inflammation, excessive mucus production, and scarring of the airways. This results in obstruction of airflow, with symptoms of difficult breathing and chronic productive cough.
In emphysema, the air sacs in the lungs become damaged, resulting in weakened lung walls and the development of large holes in the alveoli. As a consequence, the lungs become restricted during exhalation and air cannot be sufficiently exhaled.
Other common symptoms include fatigue, weakness, wheezing, shortness of breath, chest or abdominal pain, swelling in the legs, and fever.
- Smoking: Cigarette smoking is the most important risk factor for COPD, and it accounts for more than 90 percent of cases. Secondhand smoke also contributes to COPD.
- Occupation: A number of occupational pollutants, especially aerosol sprays and fine airborne particles, have been linked to an increased risk for COPD.
- Air pollution: The role of pollutants in the pathogenesis of COPD is unclear. However, the incidence of COPD is significantly increased in heavily polluted areas.
- Genetics: There is a clear genetic tendency toward the development of COPD, although specific genes have yet to be identified.
- A history and physical examination are the first steps in evaluating COPD.
- Pulmonary function testing is the most reliable diagnostic test. It can identify diminished lung function even before symptoms begin and can be used to follow the progression of the disease.
For this test, the patient breathes into a spirometer machine, which measures the speed and strength of the moving air. The result can diagnose COPD and distinguish patients who have lung obstruction, as occurs in chronic bronchitis, from lung restriction, as occurs in emphysema.
- Chest X-rays are usually normal until late in the course of disease.
- Blood testing is necessary during flare-ups.
- Acute flare-ups of COPD can be medical emergencies and may require hospitalization. It is important to identify and treat the cause of the flare-up, which is often a respiratory infection. Supplemental oxygen and medications to widen the airways (e.g., bronchodilators, such as albuterol) are the foundation of treatment. In severe flare-ups, intubation may be necessary.
- Quitting smoking is essential at any stage of the disease. Although lung damage will not be reversed (especially in advanced cases), smoking cessation will lead to improvements in lung function.
- Respiratory therapy and pulmonary rehabilitation have been shown to improve quality of life and exercise capacity.
- Physical exercise, as part of a pulmonary rehabilitation program, is essential. Exercise programs do not necessarily increase lung function, but they increase patients' ability to perform activities of daily living. Respiratory muscle training in particular is associated with significant improvements in lung capacity and function and decreased shortness of breath. As with other forms of exercise, benefits are lost if patients do not maintain their efforts.
- Continuous or nighttime supplemental oxygen provides relief of symptoms and improves mortality.
- As the disease progresses, various medications are needed to reduce lung inflammation, widen the airways, and reduce airway obstruction.
Bronchodilators (e.g., albuterol) and anticholinergic medications (e.g., ipratropium) are the most commonly used medications. However, some COPD patients do not respond to these agents.
The role of steroids is still under investigation. Inhaled steroids are often prescribed but have not been shown to be beneficial in most patients. Oral steroids may help hospitalized patients with acute flare-ups.
Antibiotics are also used during flare-ups.
- Surgery, which may include lung transplantation, is sometimes necessary in patients with advanced COPD.
Chronic Obstructive Pulmonary Disease: Nutritional Considerations
Most studies of foods and specific nutrients relate to COPD prevention, rather than treatment, and further research is necessary to establish their value. Nutritional interventions must be used along with avoidance of smoking and with appropriate medical treatment.
The following dietary factors are under investigation for their possible roles in preventing COPD or affecting its course:
- Fruits and vegetables: A number of studies have associated higher intakes of fruits and vegetables with a lower risk for COPD. However, this does not necessarily mean that fruits and vegetables prevent the disease or that lack of intake causes disease.
In a population of smokers, eating at least 4 ounces of fruit and 3 ounces of vegetables daily was associated with a 50 percent lower COPD risk, compared with individuals who ate the least amounts of these foods. Similarly, a slower rate of decline in pulmonary function was found in a general population consuming increased amounts of foods containing vitamin C. However, other studies have not shown an apparent benefit of higher fruit and vegetable intakes on COPD risk, and further clinical trials are necessary to provide a better understanding.
- Omega-3 fatty acids: In human patients with COPD, supplementation with an omega-3-containing supplement for two years significantly improved shortness of breath and reduced the rate of decline in lung function. Other evidence indicates benefits of omega-3 fatty acid supplements on exercise capacity in patients with COPD, in comparison with those on placebo. Additional controlled clinical trials are needed to determine if omega-3 fats reduce the risk or rate of progression of COPD.
- Vitamin E: Some observational studies have found protective effects of dietary (not supplementary) vitamin E intake on lung function. However, in one large study involving over 29,000 subjects, neither vitamin E (50 milligrams per day) nor beta carotene (20 milligrams a day) supplements reduced COPD symptoms. Unfortunately, clinical trials have not yet assessed the value of diets high in vitamin E for reducing COPD risk or decreasing its rate of progression.
- Maintenance of adequate body weight: In several studies, lower than ideal body weight was associated with a greater risk for death from COPD. However, it is not yet clear whether this association is because low body weight increases the risk for COPD or because COPD increases the risk for low body weight.
By some estimates, almost one in four patients with COPD is malnourished. Nutritional supplements are commonly used to correct this condition, but they have no significant effect on lung function or exercise capacity.