Why Better Sleep May Not Always Ease Cancer Fatigue

Cancer-related fatigue is distinct from sleep problems, even though the two symptoms often feel closely connected, according to Susanna M. Zick, professor in the Department of Family Medicine and Nutritional Sciences at University of Michigan.

In an interview with CURE, Zick explained that survey data show about half of patients who experience sleep problems also report fatigue. However, the other half experience fatigue without any sleep disturbance, sometimes even sleeping more than usual. This separation highlights that fatigue is not simply the result of poor sleep.

Treating sleep issues does not always resolve fatigue, and addressing depression does not consistently eliminate fatigue either. Researchers believe cancer-related fatigue may be linked to changes in the brain and low-grade inflammation, though the mechanisms are not fully understood.

Zick also noted that symptom patterns vary by cancer type. In breast cancer survivors, sleep and fatigue more often improved together, while symptoms such as anxiety, depression and pain tended to improve independently.

Transcript

How do you help patients understand that difference, especially since sleep and fatigue often feel closely connected?

That is a unique aspect of cancer-related fatigue. It is often separate and independent from other symptoms that you would think it would be connected to, like sleep. That does not mean they are not related to each other. When you look at surveys, about 50% of people who have sleep issues also have fatigue issues, and you would expect that, right? But there is another 50% who have fatigue issues and no sleep issues whatsoever. They are sleeping fine, or they are even sleeping more than usual.

So, we really know that they are two different symptoms. Even when you treat sleep, it does not mean fatigue will always go away. A lot of people think the same thing about depression. Even when you treat depression, the fatigue does not always go away. For some people it does, but for a large group it does not.

We think the mechanisms that cause cancer-related fatigue are different from those that cause other symptoms. We know it is likely due to changes in the brain and low-grade inflammation that led to these changes, but we really do not understand it very well. We have some understanding, just not a lot.

So that is the issue. It is not that you would not want to address sleep — you absolutely would — but that does not necessarily mean your fatigue will improve. It also means that if your fatigue improves and you still have sleep issues, it does not mean the sleep issues will automatically get better. We try to help people understand that distinction.

I will also say that in different cancer populations, this relationship plays out differently. When we looked at this in breast cancer survivors, those two symptoms tracked more closely together. We saw more people whose sleep improved along with fatigue. But when we looked at symptoms individually — anxiety, depression, pain — they were independent from each other. Different people experienced improvements in different symptoms rather than everyone improving across all symptoms at once.

It is interesting that these things do not always line up.

Transcript has been edited for clarity and conciseness.

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