Four out of ten Italian couples no longer have sex and a decline in the male sex drive is seen as the principle cause, according to a new study.

''Comparing sex to eating habits, one could say that Italian couples fall into four basic categories: the anorexic, the bulemic, the satiated and those who are not hungry,'' observed Chiara Simonelli, a sexologist at the University of Rome and Deputy Chairman of the European Federation of Sexology.

According to the report, 40% of 'anorexic' Italian couples are around 40 years of age, are in a solid or long-term relationship and often have children.

There is a growing trend, the report said, ''of men avoiding sex with their partners and preferring to go to a prostitute or, a sign of the times, engaging in virtual encounters on the Internet''.

The decline in the male sex drive, the study said, has tripled in the past ten years.

Only 30% of the Italian couples interviewed for the report said they were 'satiated' and had sex with a frequency considered satisfactory to both partners.

The report was drawn up by a group of sexologists, gynecologists and andrologists and will be presented at the IX congress of the European Federation of Sexology, which opens in Rome on Sunday.