STUDY finds HPV infection rate – especially of high-risk types – highest among healthy 20- to 24-year-old Chinese women.
If you are young, Chinese, smoke and have multiple sexual partners, getting a vaccination against an HPV infection of the cervix, and in particular, the sort that can lead to cancer, might be a good idea.
It is widely known that some sub-types of HPV or the human papillomavirus are associated with cervical cancer, the 10th most common cancer among women in Singapore.
However, until a recent Singapore General Hospital (SGH) study, very little local data, such as the infection rate among women in Singapore and the type of virus that they were infected with, existed.
HPV has more than 100 subtypes, of which 30-40 infect the genital system of both men and women. About 14 of these are considered high-risk, aggressive and known to cause cervical cancer. Cervical cancer has few symptoms in the early stages and is often diagnosed only in the later stages. In Singapore, one woman dies of the disease every three days, and a new case is reported every two.
According to the SGH study by Professor Tay Sun Kuie, Senior Consultant, Department of Obstetrics and Gynaecology, and Dr Lynette Oon, Senior Consultant, Department of Pathology, about 10 per cent of healthy women studied were infected with the HPV virus, with half of the infections of the high-risk types. The paper, published in the International Journal of STD & AIDS, studied nearly 900 women between the ages of 12 and 82. All of them had no history of diseases of the cervix.
“HPV infection was found in women of all ages, with the highest percentage (26 per cent) stemming from young women in their early 20s. This group also had the greatest exposure to high-risk HPV at 22 per cent,” said Prof Tay.
More of these younger women were found to also have multiple cervical HPV infections. Overall, 75 per cent of women were infected by just one virus sub-type, 18 per cent by two simultaneously, and six per cent by three. Some 30 HPV sub-types were found, including high-risk types (five per cent).
While the percentage of women exposed to the virus was fairly similar across the different ethnic groups, a slightly higher percentage of Chinese women than Indians or Malays were infected with high-risk viruses – 5.2 per cent versus 3.6 per cent and 2.3 per cent respectively for their Malay and Indian counterparts.
“While the study didn’t find statistical significance between the age a woman started sexual activity and HPV infection, the HPV infection rate was higher among women with more sexual partners,” said Prof Tay.
Smoking was found to be associated with the risk of a woman getting an HPV infection, but the partner’s smoking habit appeared to be less of a risk factor. Another risk factor was the number of years of education. The study found that the lower the number of years of formal education, the greater the incidence of HPV infection.
Not everyone who catches the infection will get cancer, in part because the virus is naturally cleared from the body. But reinfection is possible. “For a virus to induce a cancer over a period of time, the risk is 0.005 per cent. So, one shouldn’t worry that once diagnosed with the infection, she will have cancer one day. The majority don’t,” said Prof Tay.
Still, to play it safe, women should consider regular cervical screening and vaccination. Screening detects disease at the early stage, when it is more easily treated, or at pre-cancer stage, when abnormal cells appear. Vaccination can help prevent HPV infection, and is best done when young. “Vaccines are preventive measures bolstered by the immune system, so the vaccine’s effectiveness is halved when received later in life,” said Prof Tay, adding that girls as young as nine can be given the vaccine although 12 is the age that is more commonly recommended.
• This article was first published in Singapore Health, March – April 2015 issue.