Condom use may depend on the nature of a couple's relationship, rather than the partners' individual characteristics, suggests a new Dutch study.

Researchers found that couple-related factors like closeness in age and the seriousness of the relationship played a role in the variation of condom use.

"We found that when partners are more familiar with each other and when they are more alike, inconsistent condom use becomes more prevalent," Amy Matser of the Public Health Service of Amsterdam told Reuters Health.

Matser and her team surveyed a total 2,144 men and women who visited a sexually transmitted infections (STI) clinic in Amsterdam. Participants, half of whom were under 25 years old, were asked about their sexual behaviors with up to four of their most recent sexual partners.

They found condoms were used regularly in just 33.5 percent of the casual partnerships and 14 percent of the steady partnerships.

Irregular condom use was associated with certain characteristics, for example, like in people in more steady relationships. Couples of the same ethnicity and couples who engaged in anal sex or sex-related drug use, whether it was a steady or casual relationship, also used condoms irregularly.

"We should rethink of our current prevention strategies to promote condom use to see whether these methods are sufficiently capable of increasing awareness of the risk of acquiring STIs from partners who are more familiar," Matser noted.

They study was conducted in the Netherlands, but Matser thinks the findings can be applied to couples in the United States and the UK "because norms and values in these countries do not differ much from the Netherlands."

The results suggest a need for a shift in the way people look at condoms, the researchers argue.

"In my experience, people tend to be motivated to use condoms when they feel they are at risk," Dr. Luu Ireland, from the department of obstetrics and gynecology at the University of California, Los Angeles, said, adding "the only way to be safe is to practice 100 percent condom use."