Hormones are only part of the story, Murray told Live Science.
While the 0.02 decrease in female desire was small, it contrasts with male desire, which held steady over time, the researchers said.
"When an individual has had sex with their partner over the course of many, many years, it takes creativity and openness to keep things fresh and exciting," Murray said.
"Making time to be together and keep one's sex life as an important part of one’s relationship is very important, and putting in effort and keeping things fun and interesting are crucial components." A long-term trend?
"The concept of an absolute level of 'normal' or 'low' sexual desire is being replaced by the view that low sexual desire is relative to one's partner's level of desire," Murray said.
But although desire discrepancy is known to negatively affect overall sexual and relationship satisfaction, very little else is understood about it, such as whether it contributes significantly to infidelity or breakups.