"Specifically, for each additional month women in this study were in a relationship with their partner, their sexual desire decreased by 0.02 on the Female Sexual Function Index," the authors wrote online Jan. In fact, relationship duration was a better predictor of sexual desire in women than both relationship and sexual satisfaction.
She added that normalizing the fact that sexual desire may decrease over time may help both sexes to understand that this decrease does not necessarily mean anything is intrinsically wrong with their relationship, and may help couples put more effort into their sexual relationship.
"It has been theorized that men may be less inclined to admit that they have low desire as this is considered against male gender norms and masculinity," she said.
"Thus, it may be that men are not accurately reporting their level of desire and they may too experience a decrease." Murray is preparing to study whether men accurately report their levels of desire.
Knowing that many women's sexual desire diminishes over the course of a relationship could encourage both partners to be more realistic about their sex lives, and could help them weather the changes in desire as they occur.
Sex researchers Sarah Murray and Robin Milhausen, both of the University of Guelph in Ontario, Canada, asked 170 undergraduate women and men who had been in heterosexual relationships for anywhere from one month to nine years to report on their levels of relationship satisfaction, sexual satisfaction and sexual desire.