HIV prevalence and incidence in people 50 years of age and over seem surprisingly high, said a study released by the World Health Organization on Tuesday.

The report found that older people, who are more likely to risk unprotected sex than younger people, are more easily contracting the virus.

Among the aged, sexual activity is regarded as the most likely mode of HIV transmission, said the study. One reason for the increase in frequency is the use of impotence treatments that have allowed both men and women to have more sexual partners.

"Since 1998, erectile dysfunction drugs have been extending the sex life of many older individuals and, at the same time, may be extending the HIV epidemic into older age groups," the study said.

The study also found older women appear to be at higher risk of contracting HIV if they have sex without a condom because of thinning with age of the vaginal mucous membrane, which gives natural lubrication.

(Agencies via Xinhua News Agency March 4, 2009)