Scientists linked higher levels of the night-time hormone melatonin with a 75% reduced risk of advanced disease. Melatonin is produced in the dark at night and plays a key role in regulating the body's sleep-wake cycle.
Scientists studied 928 Icelandic men who had urine samples tested for levels of a melatonin breakdown. Men whose melatonin marker levels were higher than the middle of the range were 75% less likely to develop advanced prostate cancer than those with lower values.
Study leader Sarah Markt, from the Harvard School of Public Health in Boston, said: "Our results require replication, but support the public health implication of the importance of maintaining a stable light-dark and sleep-wake cycle."