People in western countries tend to have more sexual partners than those in the developing world, a study says.

Monogamy is dominant across the world, but multiple partners are more common in rich countries, according to the study published in the Lancet. This was despite developing countries having higher rates of sexually transmitted infections and HIV. They said factors such as poverty and mobility had more of a role in sexually transmitted infections than promiscuity had.

But the team added that the findings showed teenagers were not having sex earlier, contrary to popular beliefs. Researchers also said most people reported only having one sexual partner in the last year.

However, those reporting multiple partners were much higher in developed countries – up to a third of under 25s in some areas – whereas only a small percentage in Africa reported the same.