What is chronic obstructive pulmonary disease?
Chronic obstructive pulmonary disease (COPD) is a prevalent condition that is not very well known by the general public. It is sometimes called smoker’s lung because smoking is the major risk factor in Western countries for the condition. Previously, it was better known as emphysema and chronic bronchitis.
COPD is a very common disease that affects about 10% of people over the age of 45. It’s a disease that occurs as people increasingly live longer, which is one reason why the amount of COPD in the world is growing. People are dying less from other diseases such as infections and cancer, which means that COPD is becoming a more important disease for doctors to study.
COPD used to be much more common in men, but it’s now equally common in women in Western countries. This change occurred as rates of cigarette smoking among women approached that of men.
However, smoking is not the only risk factor. In many countries, particularly low- and middle-income countries, exposure to smoke during cooking is a widespread risk factor for COPD, especially in women. This non-smoking COPD probably accounts for around half of all occurrences globally as exposure to biomass smoke is very common in developing countries. There are other risk factors, such as exposure to air pollution. Air pollution may become more important in the future, as smoking declines, at least in Western countries.
Genetic influences
Only about 20% of chronic smokers develop COPD. This suggests that there must be genetic factors influencing an individual’s susceptibility to developing COPD.
For example, a rare genetic form of COPD, known as Alpha-1 antitrypsin deficiency, accounts for about 1% or less of all COPD. Inherited from both parents, this genetic disease leads to the early development of emphysema in affected individuals who start smoking.
However disappointing, further extensive research has failed to identify other convincing genetic mechanisms other than genes that determine nicotine addiction, a factor that increases chronic smoking. This may suggest that multiple genes, or epigenetic changes to gene structure, are involved in COPD development. Often, effective treatments target specific genetic mechanisms in individuals.
The role poverty plays
The most common cause of COPD is likely poverty. The respiratory disease is closely linked to poor socioeconomic conditions, which may reflect multiple risk factors. For example, smoking is more common among poor people. Such individuals are also exposed to more indoor and outdoor pollution.
Furthermore, lower-income individuals often have poor diets, another important contributing factor. For instance, a lack of antioxidants from fruit has been shown to be a factor that may lead to worse lung function.
COPD is the third leading cause of death in the world. However, its progressive onset makes it difficult to diagnose early on. Initially, lung function slowly declines, leading to shortness of breath following exertion. People with COPD then exert less, avoiding symptoms rather than seeking treatment. As a result, at least half of patients with COPD confirmed by lung tests have not been diagnosed prior. This means that underdiagnosis and inadequate treatment are problems.
Nevertheless, COPD leads to more and more shortness of breath and has a major impact on quality of life. In the most severe stage, patients often find it difficult to go out and they may be confined to their homes because they are too breathless to walk.
This is due to a progressive obstruction of the airways, caused by smoking and other risk factors, in the lungs over many years. Currently, investigators are also working to understand the role of smoking and other risk factors that lead to a narrowing of the lungs’ small airways, making it difficult for patients to empty their lungs.
In addition, there is also destruction of the spongy tissue in the lungs where gas exchange occurs. This means that the lungs are unsupported as they lose the elasticity that normal people have.
This, in effect, makes it difficult for the lungs to keep airways open. As patients breathe out, these airways tend to collapse, trapping in air. Patients with COPD therefore have overfilled lungs, which are quite uncomfortable. They find it difficult to breathe out properly, especially following exertion.
A complicated and costly disease
Patients also experience chronic bronchitis, an increased production of phlegm or sputum, due to cigarette smoke’s irritating effect on the lining of the airways. This causes the airways to make more mucus, which is then coughed up. Overall, COPD is quite a complicated disease because many changes are happening.
COPD is treated with drugs called bronchodilators that open up the small airways and allow the lungs to deflate. This makes people more comfortable and allows them to walk further before they get shortness of breath. Although bronchodilators help the symptoms of COPD, they don’t affect the underlying disease process, the progression of the disease or the mortality rate.
Researchers must identify the underlying mechanisms of COPD in order to develop disease-modifying drugs. Currently, no available treatments are capable of reversing the course of the disease or reducing mortality.
Unfortunately, the cost of treating COPD is substantial. This disease affects 350 million people worldwide and accounts for $60 billion of spending per year in the US alone. More importantly, this figure is set to increase drastically. The Harvard T.H. Chan School of Public Health has predicted that the annual cost of treating COPD globally will approach $50 trillion in about 10 years. This amount far exceeds the healthcare spending on heart disease and diabetes at present.
The only intervention that works
Obviously, smoking cessation is one of the first approaches to managing someone with COPD. Smoking drives the underlying inflammation of the lung. Furthermore, it has been demonstrated that cessation reduces disease progression. In fact, it’s the only intervention that has been shown to modify the natural history of the disease.
Nevertheless, patients with COPD often struggle to quit smoking. Nicotine replacement therapy is most commonly used but is not that effective. Drugs like varenicline also help people quit.
Despite the emphasis on smoking cessation, biomass smoke is an important issue. Providing clean cooking stoves is an important intervention. Yet, the high cost is prohibitive in low-income countries. As mentioned, poverty is the major global risk factor, but it is obviously challenging to address.
What happens with COPD over time
Sadly, COPD is unrelenting. While other respiratory illnesses like asthma can usually be effectively managed, patients with COPD continually suffer from the disease. Symptoms can be improved, but COPD’s progressive nature increasingly restricts individuals’ lifestyles, as they increasingly suffer from shortness of breath.
As with asthma, patients with COPD can experience attacks, often triggered by an infection. For example, the cold virus and other bacterial infections are common triggers that can result in an acute worsening of symptoms.
During attacks, patients may have to be hospitalised if they’re very short of breath. Cases can be treated with antibiotics and steroid tablets. However, episodes are often very frightening for patients for whom acute exacerbation can be fatal.
COPD is also a very slowly progressing disease. Individuals may develop symptoms over decades. While symptoms may not be severe initially, they are unrelenting; a patient may develop symptoms when she is 45 that progress until she passes away at 75. Patients may become short of breath when they walk up a hill, for example, which means they walk more slowly to avoid symptoms. But as time goes on, the breathlessness gets worse and worse and is brought on by less and less exertion.
Towards new treatments
I am optimistic about the future treatment of COPD because we know so much about the disease’s underlying mechanisms. As researchers continue to discover more, we will find new treatments. It may also be that there are many different types of diseases that we group together as COPD. Instead, there may be different patterns of disease in different people owing to different underlying mechanisms. If researchers can identify these idiosyncrasies, then we should be able to treat people more specifically.
For example, Alpha-1 antitrypsin deficiency is the only well-recognised genetic cause of COPD. Alpha-1 antitrypsin is a protein that’s made in the liver which protects the lungs against the breakdown of elastin fibres, as happens when patients smoke and develop COPD.
Patients with Alpha-1 antitrypsin deficiency have very low blood levels of this protein, which can be measured easily. Such patients can be treated with Alpha-1 antitrypsin protein isolated from urine.
Unfortunately, this treatment is expensive because patients require large amounts of the protein to replace what the liver is not making. While this is a specific treatment for these patients, it’s so expensive that it’s not approved in any country other than the US. Furthermore, this treatment is not entirely effective because deficient individuals can never fully offset what the liver would usually make. While this may be disappointing, researchers hope to find other specific causes of COPD for which specific treatments may be developed to stop the disease completely.
