A new study found that the timing difference between melatonin secretion and sleep midpoints may influence survival in female patients with advanced breast cancer, according to a study presented at SLEEP 2025 in Seattle.
Female patients with shorter gaps between melatonin activity and sleep patterns lived longer compared with those with wider gaps.
The study included 56 female patients with advanced breast cancer and 16 healthy, age-matched controls. All participants followed an 8-hour habitual sleep schedule, verified through 2 weeks of at-home activity tracking. Researchers then recorded 24-hour melatonin levels using blood samples collected via forearm catheter in a controlled sleep environment.
The researchers measured the timing of dim-light melatonin onset (DLMO) and melatonin midpoint, then compared these with sleep midpoint to calculate the "phase angle"—the interval between melatonin rhythm and sleep timing.
The overall timing and duration of melatonin release didn't differ significantly between the cancer and control groups. However, the phase angle between melatonin and sleep midpoints was significantly shorter in the cancer group. Within this group, those with shorter phase angles had better survival outcomes.
Using Cox proportional hazards models, the researchers found that shorter phase angles were associated with a lower risk of mortality. This association remained significant after adjusting for prior treatment, age, and typical sleep duration. Survival curves showed that within 3 years, 96% of the patients with short phase angles survived compared with 64% with long phase angles.
This survival difference appeared early and persisted over time. After 3 years, both groups experienced parallel changes in mortality, but the initial gap remained.
The findings suggested a potential link between circadian rhythm alignment and survival in advanced breast cancer. While the study didn't establish causation, it highlighted the possible role of circadian biology in cancer outcomes.
Melatonin and sleep data were collected under controlled conditions, with dim light during wakefulness and total darkness during sleep. Melatonin levels were measured using radioimmunoassay.
The study added to growing evidence connecting circadian rhythms with health outcomes in cancer. Further research may clarify whether aligning melatonin production with sleep timing can influence prognosis.
Source: Sleep
