Any substance or condition that increases cancer risk is referred to as a risk factor. The most important risk factor for developing cervical cancer is infection with human papillomavirus (HPV). However, most cancers are the result of many risk factors.
*Risk factors are generally listed in order from most significant to least significant. In most cases, it is impossible to rank the relative significance of individual risk factors with absolute certainty.
Most cases of cervical cancer occur in women younger than 50 years of age. Cervical cancer tends to affect women of African descent more often than Caucasian women. Women who practise abstinence from sex, such as Catholic nuns and women of certain religions (for example, Amish and Mormon), tend to have lower rates of cervical cancer. This is likely due to the fewer number of sexual partners that these women have, which can reduce their exposure to the human papillomavirus.
The following factors are known to increase the risk of developing cervical cancer.
Human papillomavirus
The most important risk factor for developing cervical cancer is infection with the human papillomavirus (HPV). Most women who develop cervical cancer have had an HPV infection, but not all women with an HPV infection 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.
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Smoking
Tobacco smoking has been linked to the development of cervical cancer.
Cigarette smoke contains many cancer-causing substances (carcinogens) that affect many parts of the body. Researchers have found cigarette smoke by-products in the cells that line the cervix in women who smoke. It is believed that these harmful substances may damage the cells and lead to cervical cancer. The risk of developing cervical cancer increases with the length of time a woman smokes and the number of cigarettes smoked per day.
Smoking has been associated with cervical dysplasia and invasive cervical cancer.
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Multiple pregnancies (multiparity)
Women with HPV who have given birth to 7 or more children have an increased risk of developing squamous cell carcinoma of the cervix. It is not known exactly why the risk increases with more pregnancies.
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Sexual activity
All women who have ever been sexually active are at risk for developing cervical cancer. Cervical cancer is not very common in women who have never been sexually active. Certain types of sexual behaviour can increase a woman’s risk of getting human papillomavirus (HPV), which is associated with cervical cancer.
Becoming sexually active at a young age
Early sexual activity is thought to increase the risk because many of the changes that occur in the cervical tissue during puberty make the area more vulnerable to damage.
Having many sexual partners
There is an increased risk associated with having intercourse with multiple partners, probably because of a greater exposure to HPV, which is often sexually transmitted. However, a woman can have HPV even when she has had only one sexual partner.
Sexual history of male partners
Women also seem to be at a higher risk for developing cervical cancer if their male partners have had multiple sexual partners or have had previous female partners with cervical cancer.
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Weakened immune system
A weakened immune system can increase a woman’s risk for HPV infections, which can increase the risk of cervical cancer. A weakened immune system can decrease the body’s ability to defend itself against foreign cells, such as cancer cells or micro-organisms that cause infection. The immune system can be weakened by:
- immune-suppressing drugs taken after an organ transplant to prevent rejection
- human immunodeficiency virus (HIV) infection
- HIV infection increases the chance of developing precancerous cervical changes that may develop into an invasive cancer faster than normal.
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Socio-economic status
Women with low incomes are at a higher risk of developing cervical cancer, mainly because they are less likely to get regular Pap tests.
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Diethylstilbestrol
Diethylstilbestrol (DES) is a form of estrogen that 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 DES-exposed daughters may have an increased risk of developing precancerous changes of the cervix and squamous cell carcinoma of the cervix.
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Oral contraceptives
Long-term use of oral contraceptives (commonly called the Pill) may increase the risk of cervical cancer. Women who take oral contraceptives for more than 10 years appear to have the highest risk. Risk also declines over time after a woman stops taking oral contraceptives.
The risk of developing cervical cancer in women who use oral contraceptives appears to be greater for those who have an HPV infection.
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Possible risk factors
The following factors have some association with cervical cancer, but there is not enough evidence to say they are known risk factors. Further study is needed to clarify the role of these factors for cervical cancer or precancerous changes to the cervix.
- family history of cervical cancer
- exposure to second-hand smoke
- history of sexually transmitted infections – Research suggests that long-term inflammation caused by sexually transmitted diseases may increase the risk that a woman with HPV infection may develop cervical cancer.
- Chlamydia trachomatis is a type of bacteria that is spread by sexual contact and can infect the female genital tract. Some recent studies suggest that women who have had Chlamydia infections may have an increased risk of developing cervical cancer, but further studies are needed to confirm this finding.
- Infection with the herpes simplex virus type 2 (Human herpesvirus 2 or HHV-2) may also be associated with an increased risk of developing cervical cancer.
- diet – Some studies suggest that women whose diets are low in vegetables and fruits may have a greater risk of having an HPV infection progress to early cervical cancer.
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Unknown risk factors
The following are factors for which there is not enough evidence or the evidence is inconclusive. In other words, it can’t be determined for sure whether these risk factors are or are not associated with cervical cancer.
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See a list of questions to ask your doctor about risks. Find out how to reduce the risk of cervical cancer.