Cervical Dysplasia Risk Factors
Risk factors increase the frequency of occurrence. Several risk factors have been linked to dysplasia including multiple sexual partners, early onset of sexual activity, cigarette smoking, and sexually transmitted diseases, especially human papillomavirus (HPV) and HIV infection.
Eighty to ninety percent of women with cervical dysplasia have an HPV infection. Human papillomavirus (HPV) is a group of more than 80 different viral strains. About one-third are sexually transmitted, and some types cause genital warts. HPV infects about 25 million people in the United States, and most of the viral strains are harmless.
However, the NIH Consensus Conference on Cancer of the Cervix and the World Health Organization (WHO) have concluded that several strains of HPV cause cervical cancer. The strains found most frequently in precancerous lesions and in cervical cancer are types 16 and 18. Other strains with high malignant potential include 31, 33, 35, 39, 45, 51, 52, 56, 58, and 68, and together, they account for almost 90% of cancerous lesions and dysplasia in HPV infections.
Most HPV infections resolve within 6 months and many women develop immunity. HPV often does not cause symptoms. One study found that nearly one-half of the women infected with HPV had no symptoms and a person may not even know that they are infected. Untreated HPV can result in recurrent and persistent cervical dysplasia and many experts believe that HPV is the main cause for changes in cervical cells that result in dysplasia.
Women who are infected with HIV are at a greater risk for developing dysplasia. The risk appears to increase as the number of CD4 cells (cells that play a critical role in immune responses) decreases. HIV-positive women also have a higher rate of persistent HPV infections and may be infected with the strains that are associated with severe dysplasia and cervical cancer. Women whose immune systems are suppressed for other reasons, such as by drugs that prevent rejection of organ transplants, are also at greater risk. This suggests that women with weakened immunity are more likely to be infected with HPV and to have a persistent infection that does not resolve on its own.
Nicotine and cotinine, chemicals produced from tobacco, have been found in the cervical cells of women who smoke. Men who smoke also excrete these chemicals in their semen, which comes in contact with the cervix during sexual intercourse. Tobacco chemicals may cause alterations in the cells that lead to dysplasia.
High-risk Sexual Behavior
Having multiple sex partners, having sex with a man who has had multiple sex partners, and engaging in sexual intercourse before the age of 18 are linked to cervical dysplasia. Women in these categories have a greater chance of being infected with HPV or HIV, especially if they do not use a barrier contraceptive such as a condom. These infections put them at higher risk for developing cervical dysplasia.
Between 1938 and 1971, approximately 5 million pregnant women were prescribed diethylstilbestrol (DES), a synthetic estrogen thought to help prevent miscarriage. Its use was discontinued when researchers found it to be ineffective and dangerous. The daughters of women who took DES have a higher risk for developing rare cancer of the vagina or cervix, called clear cell adenocarcinoma, and abnormalities of the cervix, vagina, and uterus.
There is growing evidence that certain vitamins, such as folic acid, play a role in cervical health. A poor diet may also cause the immune system to weaken, decreasing the body's ability to fight viruses such as HPV.
Some research shows that women who use oral contraceptives may be at a higher risk for developing cervical dysplasia. However, it is not clear if the risk is directly attributable to the contraceptives themselves. One reason may be that oral contraceptives interfere with folic acid metabolism in the cells around the cervix, and folic acid may help prevent or improve cervical dysplasia. Another reason may be that women using this method of birth control may have increased exposure to sexually transmitted diseases, compared to those who rely on a barrier method such as a condom.