A new study shows that a personalized lighting program using wearable devices and a mobile app may help lower fatigue levels in people with breast cancer (stage 1-3, posttreatment), as well as those with prostate cancer and those who had stem cell transplants.

Cancer-related fatigue is one of the most common symptoms people face during and after treatment. It refers not simply to tiredness, but exhaustion that doesn’t improve with rest and can interfere with daily activities. Researchers believe disruptions to circadian rhythms — common during cancer treatment — can lead to poor sleep and increased fatigue. Circadian rhythms are the body’s natural 24-hour cycles that regulate sleep, alertness, hormone levels, energy, and more.

Researchers at the University of Michigan Health System tested whether cancer-related fatigue could be reduced by personalizing light exposure to each person’s biological clock. Using data from a smartwatch, the Sync app created daily lighting schedules — including times for dim, moderate, or bright light — tailored to each participant’s circadian rhythms.

In the study, 138 people were randomly assigned to either follow these personalized light recommendations or stick with their usual routine. By the end of the 11-week study, participants who used the lighting program felt less tired, slept better, felt less anxious, and were able to do more physical activities than before. But these changes weren’t very different from the group that didn’t use the lighting program.

Can Light Really Help With Cancer Fatigue?

Though this study was small in size, it builds on other research suggesting that light exposure may help ease fatigue in people being treated for breast cancer. A 2023 review of 12 clinical trials found that bright light therapy (BLT) — a fixed approach using high-intensity light boxes for about 30 minutes each morning — can significantly reduce cancer-related fatigue and insomnia. Another 2022 analysis of 13 trials found the greatest benefits with light used consistently for about four weeks.

Unlike these standard one-size-fits-all approaches, the new study suggests that tailoring light exposure to a person’s body clock using wearable tech may offer added benefit.

More research is needed, still, to determine the best dose, timing, and duration of light therapy for people with cancer — and whether personalized approaches are more effective than standard ones.

If you’re living with breast cancer and are experiencing fatigue, you may want to ask your doctor about potential causes, as well as strategies to improve sleep and energy.

Learn more about causes of cancer-related fatigue and ways to boost your energy.

Find Your Team

On MyBCTeam, the social network for people living with breast cancer and their loved ones, members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Have you tried any light-based or nonmedication approaches for cancer-related fatigue? What worked best for you? Share your experience in the comments below, start a conversation on your Activities page, or connect with others in Groups.