Hi °C | Lo °C 
Women who work more than two night shifts a week face a 40% greater risk of developing breast cancer, researchers have warned.
Experts believe the hormone melatonine that potentially suppresses tumours may be disrupted by constant exposure to light during night-time hours.
The latest study, backed by the Danish Cancer Society, involved women in the Danish army who, on top of a number of factors, described themselves as either a morning person or an evening person.
On top of a 40% increased risk of breast cancer for those on night shift, the survey also found that those who had worked night shifts at least three times a week for at least six years were more than twice as likely to have contracted the disease as those who had not.
