• Learn about cancer
• Cancers at a glance
• Research highlights
• About cancer research
• Understanding 'risk'
  • What is 'cancer risk'?
  • What is a ‘risk factor’?
  • Measuring risk factors
  • Communicating risk
  • Separating fact from fiction
• Our history and achievements

What is a ‘risk factor’?

Put simply, a risk factor is something about us or our lives that increases our chances of something bad happening to us. Insurance companies say that 'being male' is a risk factor for having a car crash. And scientists have found that 'having no children' is a risk factor for breast cancer.

However, this does not mean that 'being male' causes car crashes. Nor does it mean that being having no children causes breast cancer.

It just means that, overall, more men have car crashes than women, and more women without children get breast cancer than women who have them.

This example underlines another fundamental point about 'risk' - risks are measured by looking at very large numbers of people, rather than at a particular individual.