One in five people diagnosed with hiv is over the age of 50, indicating a rise in the number of people having unsafe sex, Dutch newspapers reported on Monday.

People over the age of 50 accounted for 20% of new diagnoses of hiv in 2011, up from around 14% in previous years, according to regional newspapers Leidsch Dagblad and BN/DeStem.

In 2011, 1,100 people were diagnosed with hiv, taking the total number of people known to be carrying the disease in the Netherlands to almost 20,000.

Experts expect that in 10 years time, some 30% of people with hiv will be over the age of 60. Most of them will be gay men.

People who have hiv have a greater chance of developing diseases which are traditionally associated with the elderly, such as heart and artery disease and oesteoporosus, according to the sexually transmitted disease institute Soa Aids Nederland.

Worldwide, there has been a sharp increase in the number of over-50s with a sexually transmitted disease. In Britain, Canada and the US, for example, their number has doubled over the past 10 years, the papers said.