Swingers - straight couples who regularly swap sexual partners at organised gatherings and clubs and indulge in group sex - have rates of sexually transmitted infections comparable with those of recognised high risk groups, reveals research published ahead of print in the journal Sexually Transmitted Infections.
Those who are over the age of 45 are particularly vulnerable, indicates the research, yet swingers are largely ignored by healthcare services, representing a "missed target," say the authors.
They base their findings on the numbers of patients seeking treatment in 2007 and 2008 at three sexual health clinics in South Limburg in the Netherlands.
These clinics, which serve a population of 630,000, have systematically recorded whether a patient is a swinger since the start of 2007, in a bid to track the infection rates among this group.
During the study period, there were just under 9,000 consultations at the three clinics. One in nine of the patients (12%) was a swinger, with an average age of 43.
Swingers were among those with the highest rates of sexually transmitted infections, along with young people and gay men - groups recognised as being at high risk.
Overall, combined rates of Chlamydia and gonorrhoea were just over 10% among straight people, 14% among gay men, just under 5% in female prostitutes, and 10.4% among swingers. And female swingers had higher infection rates than male swingers.
Around one in seven of the clinic patients was aged between 35 and 45, and around one in nine (11.7%) was over the age of 45.
More than half (55%) of all diagnoses in the over 45s were made in swingers compared with around a third (31%) in gay men. One in 10 older swingers had Chlamydia and around one in 20 (4%) had gonorrhoea.
"While other risk groups for STIs, such as young [straight people] and [gay men] are systematically identified at STI healthcare facilities and provided with appropriate services, this is generally not the case for swingers," the authors point out.
This is particularly important as the practice of swinging is likely to be relatively widespread, they say.
"Although exact estimates are unavailable, the swingers' population is probably large. One of the largest dating websites for swingers estimates that there are millions of swingers worldwide," they suggest.
"Potentially they [swingers] may act as an STI transmission bridge to the entire population," they add.