Risk Factors Of Cervical Cancer In Chinese And American Women: A Meta Analysis

Aims There were many risk factors identified for cervical cancer, however, conclusions were diverged depending upon countries, regions and ethnic groups studied. Using meta-analysis, this study analyzed some 20 risk factors of cervical cancer published in the last 20 years and a comparison of risk factors was performed between Chinese and U.S. women. This study aimed at finding differences and defining risk factors for cervical cancer between the two countries and providing scientific foundation for adequate health education, definition of high risk population, effective screening and prevention of cervical cancer.Methods (1) Analyses and comparisons of disease-occurring ages of cervical cancer were performed in different ethnic groups between Chinese and U.S. women using cancer registries from 2000-2004. (2) Literature search through major Chinese and English databases using keywords related to cervical cancer and related risk factors. Based on the inclusion criteria for case-control studies, the searches found 30 original Chinese articles with 15,601 subjects (7,491 cases and 8,110 controls) and 31 original American articles with 24,262 subjects (8,896 cases and 15,366 controls). (3) Quantitative meta-analyses and comparisons were carried out on risk factors defined in Chinese and U.S. women using fixed effect model or random effect model. Unless specified, Chinese women mentioned in the study were all majority Han ethnic females.Results (1) The trends of disease-occurring ages were significantly different among different ethnic groups from China and the U.S. The major U.S. ethnic females including whites, blacks, and Hispanics, all had higher incidences of cervical cancer than Chinese Han females. Compared with American blacks and Hispanics, the American white females had a characteristic incidence of cervical cancer being higher before 44 years of age and lower after 44 years of age. (2) Chinese and American females shared 6 risk factors for cervical cancer: HPV infection : Chinese OR95%CI=19.90 [8.51, 46.57], American women OR95%CI=8.06 [5.06, 12.81]; HSV-2 infection : Chinese OR=8.05 [5.20, 12.48], American women OR=1.52 [1.20, 1.94]; younger age at first sexual intercourse (<20 years in Chinese OR=2.32 [1.41, 3.80] or <16 years in American women OR=1.80 [1.53, 2.11]); lifetime sexual partners >2 : Chinese OR=2.18 [1.24, 3.84], Americans OR=2.03 [1.71, 2.42]; active/passive smoking : Chinese OR=2.33 [1.46, 3.70], Americans OR=1.51 [1.23, 1.86]; and lower education levels (≤9 years in Chinese or≤12 years OR=3.34 [1.53, 7.28] in Americans OR=1.78 [1.34, 2.36]). (3) There were 5 risk factors specific for Chinese women: age at first pregnancy≤21 years of age; number of pregnancies >3; menopause; carrier of homozygous GSTM1 null genotype; and carrier of homozygous p53 codon72 Arg/Arg in Chinese minority Uygur women. (4) There were 7 risk factors specific for American women: number of abortion >1; annual income≤US$20,000; marital status (single/divorced/separated/widowed); interval since last Pap test >10 years; never used barrier contraceptives; non-user of intrauterine device use (IUD); and carrier of p53 codon72 Pro/Pro genotype. (5) There were 4 factors that could not be risk factors or could not be determined to be risk factors for cervical cancer at present time: number of pregnancies in American women; number of births (<2 could be protective factor in Chinese women); oral contraceptive use; and carrier of homozygous p53 Arg/Arg.Conclusions This study is the first to analyze and compare risk factors of cervical cancer published in the last 20 years for both Chinese and U.S. women and has reached the following conclusions: (1) In recent years, cervical cancer has shown trends of increasing incidences and decreasing or younger age in the ethnic groups investigated in both China and the U.S. (2) In the 6 shared risk factors between Chinese and U.S. women, at least 3 may be relevant to HPV infection. For example, younger age at first sexual intercourse could increase the chance of earlier HPV infection; more lifetime sexual partners would mean the higher opportunity to be infected with HPV; and smoking could increase the HPV viral load in infected individuals. (3) This study has defined for the first time that there are specific risk factors of cervical cancer for Chinese women (5 factors) as well as for American women (7 factors), respectively. (4) The current Meta-analyses revealed that 4 factors previously thought risk for cervical cancer may not be risk factors at all or cannot be determined to be risk factors for cervical cancer at present time.The observations and conclusions obtained in this study have indications in that women's health education, screening, and prevention of cervical cancer should be strategized based upon common as well as specific risk factors to local nationals in order to make the strategies more efficient and more cost-effective.