New York, Oct 22 (IANS): Smoking and having oral sex with multiple partners may put men at increased risk of developing a type of head and neck cancer that is triggered by exposure to the human papilloma virus, known as HPV-related oropharyngeal cancer, warns a new study.

The risk was much lower among women, anyone who did not smoke, and people who had less than five oral sex partners in their lifetimes, found the study published in the journal Annals of Oncology.

"Most people perform oral sex in their lives, and we found that oral infection with cancer-causing HPV was rare among women regardless of how many oral sex partners they had," said one of the study authors Amber D'Souza, associate professor at the Johns Hopkins Bloomberg School of Public Health in the US.

"Among men who did not smoke, cancer-causing oral HPV was rare among everyone who had less than five oral sex partners, although the chances of having oral HPV infection did increase with number of oral sexual partners, and with smoking," D'Souza added.

There are over 100 different kinds of HPV but only a few are known to cause cancer; infection with HPV 16 or 18 is already known to trigger most cervical cancer, and HPV16 also causes most oropharyngeal cancer.

The researchers analysed data from 13,089 people, aged 20-69, taking part in the US National Health and Nutrition Examination Survey (NHANES) who had been tested for oral HPV infection.

They used the numbers of oropharyngeal cancer cases and deaths from US registries to predict the risk of cancer from oral HPV infection.

They investigated the prevalence of cancer-causing HPV found in oral rinses and the numbers of new cases of oropharyngeal squamous cell cancer (OSCC) - the commonest type of oropharyngeal cancer.

The researchers found that women who had one or no oral sex partners during their lifetimes had the lowest prevalence of oral infection with cancer-causing types of HPV.

The prevalence of infection increased slightly to 1.5 per cent among women with two or more oral sex partners.

Among men, the lowest risk group were those who had one or no oral sex partners in their lifetimes, with a prevalence of oral HPV infection of 1.5 per cent.

The prevalence of infection was highest 15 per cent among men who smoked and had five or more oral sex partners, the study found.