Sleep influences cancer risk through multiple pathways — natural killer cell activity (which identifies and destroys cancerous cells) peaking during sleep and measurably reduced by sleep deprivation; melatonin's direct anti-tumor effects including anti-proliferative signaling and antioxidant protection of DNA from replication errors; systemic inflammation elevation facilitating tumor microenvironment development; and the disruption of tumor-suppressing gene expression by circadian disruption in shift workers, who have WHO-classified occupational cancer risk from circadian disruption.
Role
Cancer risk reduction through sleep is among the most important and least communicated aspects of sleep health — with the WHO's classification of shift work (a condition of systematic circadian disruption) as a probable carcinogen providing official recognition of the sleep-cancer connection. Natural killer cells are the immune system's primary anti-cancer defense, and their activity is directly proportional to sleep quality and duration — making every night of adequate sleep a dose of immune anti-cancer activity, and every night of deprivation a reduction in that protection. Most people making dietary and lifestyle anti-cancer choices have never been told that their sleep quality is directly influencing the primary immune mechanism through which the body routinely eliminates cancerous cells before they proliferate.