Links Between COPD And Peripheral Muscle Wasting?
A secondary condition that sometimes occurs with COPD is Peripheral Muscle Wasting. What is this? Can it be prevented or reversed? Here's all you need to know.
What is peripheral (skeletal) muscle wasting?
It is a medical condition that occurs when skeletal muscle tissue, or the tissue used to help you move your arms and legs, wastes away (atrophies).1
Prolonged sitting and bed rest can cause muscle atrophy, increasing the risk for falls and reducing quality of life due to inactivity and increased need for healthcare services, both independent of lung function. Considering COPD is also often associated with osteoporosis (fragile bones), this also increases the risk for fractures, particularly hip and vertebral fractures, and this further diminishes the ability to stay active, further hampering quality of life, and increasing the the need for hospital and nursing home admissions.2
Who does muscle wasting affect?
Along with affecting the COPD population, it has also been known to impact those with heart failure, kidney failure, cancer, AIDS, and other chronic conditions. 3
When I started researching this, I guessed that muscle wasting would only be a concern for those diagnosed with severe COPD when exertion became extremely difficult. However, estimates made in the early 2000's speculated that up to 50% of people with either mild or severe disease also suffered from some degree of skeletal muscle wasting. Other studies seemed to corroborate these estimates, showing that about 50% of the general COPD population suffered from weight loss contributed to skeletal muscle wasting.3-4 However, more recent evidence seems to suggests the prevalence is about 32% among the entire COPD population.2
Which muscles waste away?
The greatest concern among the COPD population are the peripheral skeletal muscles, particularly those in the arms and legs. This makes sense, considering these muscles are needed to stay physically active. Skeletal muscles in the arms tend to maintain their strength as they are used for daily activities. Of greatest concern are skeletal muscles in the legs, which are less likely to be used due to sedentary living. Weakness, or loss of strength, in this muscle was the main determining factor of diminished tolerance for exercise in 40-45% of COPD patients, at least according to one study.2-3
Why does muscle wasting occur?
There are a few prominent theories as to why muscle wasting occurs.
Many people with COPD feel winded when they exert themselves, or at least fear that exertion will make them feel winded. This results in a sedentary lifestyle that makes skeletal muscles prone to atrophy and wasting.4
Mediators of inflammation
COPD is the result of an abnormal immune response to chemicals (such as in the air at your work or in wood or cigarette smoke) that were inhaled day after day after day, year after year after year. This immune response involved the release of chemicals (mediators of inflammation) that cause airway and lung tissue inflammation. This inflammation becomes severe and eventually causes airway scarring (chronic bronchitis) and lung tissue destruction (emphysema).
Modern evidence seems to suggest that these same chemicals can get into your bloodstream and thereby affect more body systems than just your lungs. One of these other systems affected is your skeletal muscle system, where these chemicals are thought to contribute to the breakdown of the proteins that make up skeletal muscles.2,4
Inhaled corticosteroids, and sometimes systemic corticosteroids, are a type of medicine often used to reduce airway inflammation to control and prevent COPD flare-ups. High doses short-term to treat flare-ups don't seem to be the culprit here, it's small doses long-term to prevent flare-ups that are most commonly associated with muscle wasting.2 A possible reason corticosteroids may contribute to muscle wasting is that they cause a reduction in testosterone, which may contribute to muscle wasting.2,4
This is a medical term referring to low tissue oxygen levels. This is a condition where tissues, such as muscle tissue, receive less oxygen than normal. Some studies show that this may also contribute to low testosterone levels and muscle atrophy.
Chemicals in cigarette smoke and inflammatory chemicals may also cause an increase in free radicals (molecules with electrons missing) that steal electrons from cells and cause tissue damage. This is now believed to be a major cause of COPD, and is suspected to also be a cause of muscle wasting in COPD patients.2
Chemicals in cigarette smoke
This is suspected because about 90% of people diagnosed with COPD are current or former smokers. There are over 4,000 chemicals in cigarette smoke, many of which may cause changes inside your body, including genetic changes, that cause the breakdown of muscle tissue. These chemicals have also been shown to cause oxidative stress and the release of inflammatory mediators.2
It could also be the result of malnutrition, vitamin D deficiency, or even aging.2 The fact that there are so many theories about potential causes is evidence that further research is indicated to learn more about the links between COPD and peripheral muscle wasting.
Can muscle wasting be treated and prevented?
In order to prevent atrophy, muscles must stay active. However, when you’re having a hard time breathing, especially when you exert yourself, staying active can become a chore. In some cases, it may seem impossible. This is why it’s so important to get an early diagnosis, and to work with your doctor to develop a COPD treatment program to help you breathe easy. A key part of this treatment program may involve staying as active as possible. Such activity may be as simple as walking around the house, or leaving your house and going to the store. It may also involve working with physical therapy to learn exercises to help you stay physically active.3
Can it be treated and prevented with medicine or nutritional supplementation?
At the present time there are no medicinal treatments for muscle wasting. There are some medicines and nutritional supplements that are being studied, or will potentially be studied in the future, although none are available at the present time. So, this means treatment usually involves working with your doctor and physical therapy to develop strategies for keeping your muscles active to help you maintain or rebuild muscle mass.
What does all this mean for you?
If estimates are accurate about the prevalence of muscle wasting in COPD being 50% or even greater, this puts a spotlight on the need for determining strategies for preventing and reversing it. Researchers must continue to study it to find safe and effective medical treatments for preventing and reversing skeletal muscle wasting. Plus, physicians must place physical activity and/ physical therapy as key elements to any COPD treatment program.
It means educating yourself and staying as active as you can. The importance of this cannot be understated. In fact, staying active with COPD is so important that it has been written about by nearly every expert on this site, including our editors, caregivers, nurses, and even those living with it. Most experts now contend that you can live a long, quality life with COPD, and a key to accomplishing this is staying physically active.
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