Other risk factors
There are many other factors that affect a person's chances of developing cancer. The most important ones are listed below.
Age
Age is an important risk factor for cancer. This is because the longer we live, the greater the number of potentially cancer-causing mutations in our DNA. This is why the disease is so much more common in older people - nearly two-thirds of all cases of cancer diagnosed in the UK occur in people over 65 years old.
Viruses
Some viruses are linked to certain types of cancer. This does not mean that these cancers spread from person to person like an infection, and does not mean that everyone infected with these viruses will develop cancer.
The following viruses are linked to cancer:
- the Human papilloma virus (HPV) is the major cause of cervical cancer
- the Hepatitis B and C viruses can cause primary liver cancer
- the Human T-cell leukaemia virus can cause leukaemia
- the Epstein-Barr virus (EBV) can occasionally cause some types of childhood cancers, carcinomas and lymphomas. Exactly how it does this, and under which circumstances, is not well understood.
- the Human immunodeficiency virus is linked to several cancers as it weakens the immune system (see below)
Weak immune system
People who have problems with their immune system are at higher risk of developing cancer, probably because they are less able to combat infections by viruses that are linked to cancer (see above). This group includes people who:
- have had an organ transplant and are taking drugs to suppress their immune system
- have HIV/AIDS
- are born with one of several rare genetic diseases that affect the immune system.