Why Women Lose Interest In Sex Before Men

The Female Sexual Function Index

Sex after marriage is a tricky endeavor. Not because it isn't hot in the beginning, but because it's so difficult to keep it that way. According to a new study, the longer a woman is in a relationship, the more her sexual desire decreases.

READ: Is It Normal to Lose Your Sex Drive After Childbirth?

Researchers at the University of Guelph in Ontario, Canada, surveyed 170 students, male and female, who had been in heterosexual relationships for anywhere from one month to nine years about their sex lives.

The students were asked to grade their relationship satisfaction, sexual satisfaction and sexual desire on a scale of 1.0 to 6.0, according to a system called the Female Sexual Function Index.

While the levels of satisfaction reported were pretty consistent (most said they were satisfied), women's desire dropped the longer they stayed in a relationship.

"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 researchers wrote in the study, published online in the Journal of Sex & Marital Therapy.

READ: 5 Ways Relationships Are Good for Your Health

Men, however, reported no decrease in desire.

So what does this mean? Do some women just grow tired of the same sexual partner, or is sexual desire more complicated?

According to evolutionary scientists, male desire for sex is supposed to remain high throughout his life so he can produce as many offspring as possible. But for women, who physically cannot bear children during old age, their desire levels are designed to taper off in parallel with their physical limitations.

Of course, no matter what the cause, researchers say a better understanding of this natural change in desire can help us understand each other better and become more able to work through the problems of a long-term relationship.