Risk factors for cervical cancer
A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. Infection with human papillomavirus (HPV) is the most important risk factor for cervical cancer.
Most cases of cervical cancer occur in women younger than 50 years of age. Cervical cancer tends to affect women of African ancestry more often than Caucasian women. Women of certain religions (for example, Catholic nuns and Amish and Mormon women) also tend to have lower rates of cervical cancer. This is likely due to having fewer sexual partners, which can lower their exposure to HPV.
Risk factors are generally listed in order from most to least important. In most cases, it is impossible to rank them with absolute certainty.
Known risk factors
There is convincing evidence that the following factors increase your risk for cervical cancer.
Most women who develop cervical cancer have had an HPV infection. But having an HPV infection doesn’t mean that you will develop cervical cancer. Many different types of HPV can infect the cervix, but only some of them cause abnormal changes to cells that may turn into cancer.
Find out more about human papillomavirus (HPV).
Smoking increases the chance of an HPV infection not going away on its own. If an HPV infection doesn’t go away, it can lead to the development of cervical dysplasia, which is a precancerous condition of the cervix, and cervical cancer.
Cigarette smoke contains many cancer-causing substances, or carcinogens. They affect many parts of the body. Researchers have found by-products of cigarette smoke in cells lining the cervix in women who smoke. They believe that these harmful substances may damage the cells and allow an HPV infection to stay in the body. The longer and the more cigarettes you smoke each day, the more your risk increases.
Parity is the number of times a woman has given birth. Multiparity, or giving birth more than once, has been linked with cervical cancer risk. The more children a woman gives birth to, the greater her risk of cervical cancer.
Having given birth may also increase your risk of an HPV infection developing into cervical cancer. This may be because high levels of sex hormones are present during pregnancy and childbirth or because of other factors that we don’t yet fully understand.
Being sexually active means more than having intercourse with someone. It can mean:
- any genital skin-to-skin contact
- having oral sex
- having intercourse
All women who have ever been sexually active are at risk for developing cervical cancer. This is because sexual activity potentially exposes you to HPV. Women who have never been sexually active rarely develop cervical cancer.
Becoming sexually active at a young age can increase the risk of cervical cancer. Researchers think this increases the risk because the cervix changes during puberty. These changes make the area more vulnerable to damage.
Certain types of sexual behaviour increase a woman’s risk of infection with HPV. Having intercourse with many partners can increase exposure to HPV, which is transmitted by sexual contact. For this reason, having many sexual partners is linked with a higher risk of cervical cancer. But a woman can have HPV even when she has had only one sexual partner.
Women also seem to be at a higher risk for developing cervical cancer if their male partners have had many sexual partners or female partners with cervical cancer.
The immune system can be weakened by immune-suppressing drugs that people take after an organ transplant to prevent their body rejecting the organ. It can also be weakened by infection with the human immunodeficiency virus (HIV).
A weakened immune system can lower the body’s defences against infection and disease. It can increase a woman’s risk for HPV infections and the chance that an HPV infection won’t go away. When the immune system is weakened, there is a greater chance that precancerous changes to cells in the cervix can develop into cervical cancer. Women with weakened immune systems may develop cervical cancer from precancerous changes faster than women with normal immune systems.
Women with low incomes have a higher risk of developing cervical cancer. This is mainly because these women are less likely to get regular Pap tests.
Diethylstilbestrol (DES) is a form of estrogen. It was used between 1940 and 1971 to treat women with certain problems during pregnancy such as miscarriages. It has not been approved for use in pregnant women since the 1970s.
Daughters of women who took DES during their pregnancy have a higher than average risk of developing a rare type of cervical cancer called clear cell carcinoma. Some studies also suggest that daughters of women who took DES may have a higher risk of developing precancerous changes of the cervix and squamous cell carcinoma (SCC) of the cervix.
Oral contraceptives are commonly called the pill. Taking oral contraceptives over a long time may increase your risk of an HPV infection developing into cervical cancer. Women who take oral contraceptives for more than 10 years appear to have the highest risk of cervical cancer. This risk goes down over time after you stop taking oral contraceptives.
The following factors have been linked with cervical cancer, but there is not enough evidence to show they are known risk factors. Further study is needed to clarify the role of these factors for cervical cancer.
Family history of cervical cancer
Some studies have shown that women who have a mother or sister diagnosed with cervical cancer have a greater risk of developing this cancer than women without a family history. More research is needed to clarify whether this is due to genetics or common lifestyle factors.
History of sexually transmitted infections
It is thought that having a sexually transmitted infection (STI) increases the chance that a woman will also have HPV. Research suggests that long-term inflammation caused by certain STIs may increase the risk of cervical cancer in women with HPV.
Chlamydia trachomatis is a type of bacteria. It is spread by sexual contact and can infect a woman’s genital tract. Some recent studies suggest that women with HPV who have had chlamydia may have a higher risk of developing cervical cancer. Further studies are needed to confirm this finding.
Herpes simplex virus type 2 is also called Human herpesvirus 2 or HHV-2. Infection with this virus may also be linked with a higher risk of developing cervical cancer in women with HPV.
Unknown risk factors
It isn’t known whether or not the following factors are linked with cervical cancer. It may be that researchers can’t show a definite link or that studies have had different results. Further study is needed to see if the following are risk factors for cervical cancer:
- exposure to second-hand smoke
Questions to ask your healthcare team
To make the decisions that are right for you, ask your healthcare team questions about risks.
What’s the lifetime risk of getting cancer?
The latest Canadian Cancer Statistics report shows about half of Canadians are expected to be diagnosed with cancer in their lifetime.