Study Reveals How Sleeping Late May Affect the Body's Cancer-Fighting Defences - Video

Staying up late may be more than a nuisance. New research suggests that unhealthy sleep patterns may be associated with a higher risk of breast cancer, although the findings do not prove that late nights directly cause cancer.

Published in BMC Cancer, the study analysed sleep patterns and breast cancer risk among 159,452 women in the UK Biobank. During follow-up, 7,291 participants developed breast cancer. Researchers found that women with an unhealthy sleep pattern had a 10% higher breast cancer risk than those with healthier sleep patterns, after accounting for demographic and lifestyle factors.

The researchers identified biological signals involving immune regulation and inflammation. These findings suggest that disrupted sleep and circadian rhythms could influence processes involved in cancer defence.

The body’s circadian rhythm is an internal 24-hour clock that helps coordinate sleep, hormone release and immune activity. Repeated disruption of the normal light-dark cycle may affect immune surveillance, including natural killer cells that help identify abnormal cells.

Night-time light exposure may suppress melatonin, a hormone involved in regulating sleep. Late-night phone use, television viewing and bright indoor lighting can delay sleep and extend exposure to light after dark. Sleep disruption may influence inflammation, hormone regulation and DNA repair, all of which are relevant to cancer biology.

However, the study did not directly measure artificial light exposure at night and cannot establish that staying up late or using a phone causes breast cancer. It was observational, so other factors may contribute to the association.

Researchers found that genetic susceptibility could influence risk, with the highest risk observed among women with higher genetic risk and unhealthy sleep patterns.

The findings do not mean occasional late nights cause cancer. They mainly highlight the importance of maintaining regular, healthy sleep patterns consistently over time.

REFERENCE: Chang, X., Zuo, S., Wang, Z. et al. Sleep patterns and breast cancer risk: a prospective cohort study integrating multi-omics and machine learning. BMC Cancer (2026). https://doi.org/10.1186/s12885-026-16641-8