We learn the difference between cause and effect at an early age. Before we have the words to express an idea, we learn that when our bellies hurt, we cry out in pain. When we cry out in pain, someone comes and attempts to attend to our wails. Usually, one of the first solutions is to feed us. When we have food in our bellies, the pain abates. A little connection of the dots tells us that crying gets the pain in our stomachs to go away.
Unfortunately, the concept of cause and effect gets muddled in our minds as we get older. Soon, we observe two things that commonly happen in the same order, thus we conclude that the first caused the second. The rooster always crows just before sunrise, but the rooster does not cause the sun to rise. The pattern was deceptive.
However, these patterns are valuable in medicine. For example, people with more muscle mass tend to see a slower progression of idiopathic pulmonary fibrosis (IPF), and therefore a longer survival average.
A new study in a medical journal called Respirology shows a correlation between the fat-free mass index (FFMI) of a person and the progression of the disease. This is a positive correlation (as one goes up, the other goes up as well). The FFMI is similar to the more commonly referenced body mass index (BMI) in that it measures the body’s density. However, FFMI takes into account the amount of muscle mass present in the body, rather than just the height-to-weight ratio.
The connection seems to imply that having more muscle mass means IPF will not progress as quickly.
However, another way of looking at this is to think about who has a higher muscle mass. Generally speaking, people who exercise more and who eat healthy meals tend to have more muscle mass. More exercise is known to cause improved cardiovascular and respiratory health. It only makes sense that people with healthier lungs and lifestyles will not buckle under the pressure of IPF as readily as people who don’t.
All in all, we should not assign a true causal relationship to muscle mass improving survival rates or slowing progression. But we should use what we know about the correlation between the two to make better decisions about when to start treatment and how better to assess the progression of the disease.
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