Working more than 30 years of night shift work appears to increase the risk of breast cancer by 2.21 fold when compared to no night shifts in the general population. These trends were the strongest in the health occupations, although risk increased in nonhealth occupations also. The mechanism is suspected to involve melatonin which regulates circadian rhythm based on light exposure and may protect from cancer.
PositiveTip: Trapped in night shift work? Maybe you could apply for a change or pursue a new career.