Researchers link chemotherapy treatment to disrupted circadian rhythms affecting sleep and behavior.
Cancer treatments often leave patients dealing with more than the disease itself. For many, one of the less visible but deeply disruptive effects is a disturbance in the body’s natural daily rhythm. Nearly half of patients going through chemotherapy report irregular sleep, fatigue, and mood changes tied to changes in their circadian rhythm. This rhythm, controlled by a master internal clock in the brain, helps regulate the sleep-wake cycle, hormone release, and even digestion. What has puzzled researchers for years is why chemotherapy seems to influence this rhythm when the drugs are not thought to reach the brain in significant amounts.
A recent study led by Leah Pyter at Ohio State University set out to answer this question. Her team looked specifically at paclitaxel, a drug commonly used in breast cancer treatment. Using female mice, the researchers explored both genetic and behavioral changes tied to circadian function after chemotherapy exposure. Female mice were chosen because breast cancer primarily affects women, making the model more relevant.
The findings showed that paclitaxel disrupted the usual daily patterns of genes involved in the biological clock. In untreated mice, these genes switched on and off at expected times throughout the day. In those given chemotherapy, the cycle flattened out, suggesting that the natural rhythm of the internal clock had been disturbed. This was significant because the master internal clock is designed to respond to cues from the environment, particularly light. To test whether this ability was impaired, the researchers exposed mice to controlled light challenges. Healthy mice adapted to the changes, but those that had received chemotherapy showed less flexibility.
The combination of altered gene activity and poor adaptation to light signals points to both molecular and behavioral impacts on the brain’s timekeeper. As first author Zoe Tapp explained, it was surprising to see that the main circadian clock in the brain was affected without being directly targeted by paclitaxel. This suggests an indirect pathway of influence that still manages to alter brain function.
For patients, these findings may help explain why so many experience disrupted sleep patterns during treatment. Chemotherapy is already associated with nausea, fatigue, pain, and reduced appetite. Adding circadian disruption on top of these side effects can make daily life much harder. The research highlights how cancer therapy may interfere with the body’s ability to maintain balance in ways not yet fully understood.
Leah Pyter noted that better understanding this link could open doors for supportive care strategies. If circadian rhythm pathways in the brain are shown to be consistently affected by chemotherapy, doctors may be able to provide patients with tools to maintain stronger rhythm signals. This might involve structured exposure to daylight, carefully timed meals, or sleep hygiene practices that reinforce the natural clock. While more research is needed before such measures can be formally recommended, the potential is there to improve quality of life without adding more drugs to an already intense treatment process.
This work also raises broader questions about how cancer therapies interact with the nervous system. If a drug like paclitaxel, which is not known to cross into the brain in large amounts, can still alter brain function, other side effects may be occurring in ways not yet recognized. Exploring these indirect connections may provide a fuller picture of how treatment affects not only the tumor but the entire body.
Cancer research often focuses on survival but addressing how patients live during treatment is just as important. By investigating how the body’s clock is disrupted, studies like this one provide insight that could eventually make treatments more tolerable. As circadian science continues to grow, it may offer cancer patients a better chance at preserving normal daily rhythms even while undergoing aggressive therapy.
Sources:
Exploring whether chemotherapy disrupts biological clock in the brain to impair circadian rhythms
Join the conversation!