HPV screening is very important for the prevention and detection of cervical cancer. However, cervical cancer screening started late in China, and there is still a big gap between the current promotion and developed countries. In addition, the data of HPV infection rate and genotype distribution in different regions are not comprehensive, especially in the remote areas in Western and Northern China. There is a lack of relevant data to guide the health education of cervical cancer. Therefore, collecting and analyzing the epidemiological evidence of local HPV infection can provide a reliable scientific basis for the prevention, treatment, and elimination of human papillomavirus infection-related diseases.
Shannan city of Tibet Tibetan Autonomous Region was located in Northwest China. Its economy was underdeveloped, and the prevention and screening of cervical cancer were also quite backward. Therefore, improving the screening of HPV in Tibet was particularly important for the primary prevention of cervical cancer in Tibet. This is not only conducive to women's health but also can save a lot of medical expenses for the country. Studying the prevalence and genotype distribution of human papillomavirus in different regions and periods is highly important for cervical cancer screening and evaluating the effectiveness of the human papillomavirus vaccine for women. For the last 20 years, the world has made great efforts to generate epidemiological data on cervical HPV-DNA. In China, although certain studies have been performed to assess the prevalence and incidence rate of human papillomavirus genotypes in Tibet, they are based on small samples. Our study is the first large-scale sample study in Tibet.
Due to the differences in regional, population, living environment and lifestyle, and human papillomavirus DNA test methods, the reported results of global human papillomavirus distribution vary from study to study. A meta-analysis of a total of 1,016,719 screening people included in 194 studies around the world showed that the adjusted infection rate of HPV in the global population with normal cytology was 11.7%, of which the infection rate was the highest in sub-Saharan Africa (24.0%), Eastern Europe (21.4%) and Latin America (16.1%) and the lowest in Western Asia (1.7%). According to research, the overall prevalence of human papillomavirus infection in China is 15.54%. In our study, the rate of human papillomavirus infection among women in Shannan City, Tibet was 8.16%, lower than the global average, lower than the Chinese average, and lower than many other cities or regions in China. Some researchers speculated that the variability of HPV prevalence in China was due to China's large population and territory. At the same time, the level of economic development and population migration also led to the differences in the distribution landscapes of human papillomavirus among regions. As shown in Table 4, both Beijing and Shanghai were economically developed cities, but the HPV infection rate varied greatly. The reason may be that Beijing, as China's political, cultural, and economic center, had good medical conditions and protection strategies. Otherwiese, Shanghai's economic development level was also very high, but due to a large number of foreigners and migrant population, the city was expanding and the population composition was complex, resulting in a high rate of human papillomavirus infection. In Shannan City, although the economy and medical treatment were relatively backward, the HPV infection rate was the lowest. The reason behind it may be the simple folk customs, the majority of the people who believe in Tibetan Buddhism and the conservative traditional concept of sex, which was similar to Xinjiang Provence. Another study on the HPV infection rate in Tibet which was 9.19% (279/3,036), which supports this conclusion.
Information on the distribution of human papillomavirus infection in different age groups is extremely important for the design of human papillomavirus preventive vaccines in specific age groups. What many studies have in common is that the first peak occurs in the younger age group (just after the beginning of sexual relations). In some areas, the second peak can be observed at the age of > 45 or > 55 or > 65, while in some other areas, no second peak can be observed. In conclusion, age-specific HPV distribution is either shown as a bimodal curve (including "U" curve) or a left inclined unimodal distribution. In this study, age-specific HPV distribution showed a "U" curve. The first peak of human papillomavirus infection occurred in the age group ≤25 years old (12.68%), then decreased gradually, reached the lowest in the age group 46-55 years old, and then increased gradually. The reason for this trend may be that young women were sensitive to human papillomavirus soon after sexual activity due to immature immune protection. With the stimulation of immune response, a large part of primary HPV infection would be temporary and would be cleared spontaneously, so the HPV infection rate decreased gradually. The immune ability of elderly women decreased with age, especially in the premenopausal and postmenopausal women, which resulted their ability to eliminate previous and new HPV infections being weakened. Furthermore, as past (latent) infections reappeared, both factors led to a higher HPV infection rate of elderly women. Based on these findings, the earlier young women were vaccinated with HPV vaccine, the higher the antibody titer and the better the protection. Once HPV infection was detected, HPV viral load should be continuously monitored and cervical biopsy should be performed regularly.
Although a variety of studies provided large-scale information on the recent HPV prevalence and genotype distribution in Shannan City, Tibet, China, there were still some limitations. First, most cervical screening tests received by patients did not carry out detailed HPV typing, nor did they be combined with cytology. Women included in some studies were unable to obtain cervical cytological or histological results. Therefore, it is impossible for doctors or researchers to associate HPV infection and genotype distribution with different cervical abnormalities. Secondly, the collection of personal information of patients was not complete. Tibet had a high altitude and a wide area. There was a variety of distinctive information about the nationality, living habits, reproductive history, climatic conditions cultural, and other backgrounds of the population in this area. Unfortunately, it was not recorded in this study so that we couldn’t specify the impact of these different backgrounds on the rate of HPV infection. In addition, some studies had shown that human papillomavirus infection may lead not only to cervical cancer but also to oropharyngeal cancer and head and neck cancer. Therefore, it was suggested to also focus on the relationship between HPV infection and oropharyngeal cancer, and head and neck cancer in Tibetan women in future research. In addition, obtaining data on human papillomavirus infection in Tibetan men could be regarded as a potential direction for future research.
After all, our study revealed the HPV infection rate and genotype distribution of women from Shannan City, Tibet, China. This information may provide guidance and suggestions for the prevention of cervical cancer for women in this area. According to the current results, young women should be vaccinated with HPV vaccine as soon as possible, and elderly women should focus on crevice screening.