Social researcher and author Wednesday Martin has previously told the ABC at least six longitudinal studies — in total tens of thousands of adults in the age range of 18 to 70 — showed "consistently that in a long-term committed exclusive relationship, women stop wanting to have sex in years one to four".
Whereas men, she says, are "pretty happy having sex with their long-term partners for nine or 12 years without reporting boredom".
Women crave novelty and excitement in the bedroom, says Ms Waugh, and the burden of mental load doesn't help to increase their sexual interest, either.
'Sex that's not interesting enough'
Esther Perel, a psychotherapist who has spent years studying intimacy and monogamy, has been quoted as saying while men's sexual desire in long-term relationships declines gradually over the years, women's "plummets".
"It's always been translated as, 'Well, that's because women care less about sex', rather than 'It's because women care less about the sex they can have in their committed relationships, which is often not interesting enough for them.'"
One study from 2012 found for women only, lack of interest in sex was higher among those in a relationship of more than one year in duration. Research from 2018 found the longer the duration of the relationship, the more relationship quality could influence sexual desire in women.
And while a 2023 study found sexual boredom to be more common for men in heterosexual long-term relationships, they still had high sexual desire for their partner overall, whereas women's desire for their partner declined as their boredom increased.
Ms Waugh says without "effort or novelty", women's sexual desire can wane over time.
The mental load
In addition to the role monotony plays in this picture, researchers are increasingly looking at how the mental load factors into it.
A study from Swinburne University of Technology in 2022 found that growing inequity over the course of a relationship was often at the root.
Women are largely responsible for the "invisible and visible" work in the home, says Coby Baker, a sexologist in Melbourne/Naarm and south-west Victoria.
"Women, generally speaking, take on more things like doing the kids' school lunches, pick-up and drop-off, thinking about the mother-in-law's birthday present.
"Sex just becomes another thing on the to-do list."
In relationships where household and caring duties are divided more equally, she says women are "more physically and emotionally available for sex".
Having to parent a partner, rather than being able to nurture an emotional connection, can also kill sex drive, says Ms Baker.
More broadly, she says the predictability of day-to-day life means the excitement of that early spark in the relationship fades.
This is especially true for women, who are more likely to experience responsive desire (sexual desire that arises in response to stimulation or arousal, rather than spontaneously).
Women 'putting up' with it
Ms Baker says while some women experiencing a lack of desire or sexual dissatisfaction may choose to end or open the relationship, or even have an affair, the more common outcome is "putting up with bad sex".
"They give men sex because they are tired of being nagged for it. Then they start to become resentful."
Ms Waugh says many women aren't taught to prioritise their own pleasure, and instead treat sex as something they give rather than get to enjoy.
And they often want to change things, but aren't sure how to approach it.
"They don't want to be unhappy. They want more. They want a partner that understands them and their needs."
A couple's problem
Ms Baker says women should remember low desire isn't something that needs to be "fixed".
The Swinburne University research mentioned earlier found that while relationship inequities may have affected dyadic desire (the sexual desire one feels for another), they didn't significantly impact solo desire, which is individual feelings.
"This suggests women's low desire isn't an internal sexual problem to be treated with mindfulness and jade eggs, but rather one that needs effort from both partners," the authors wrote.
Many couples do find their way back when this issue is met with curiosity instead of criticism, says Ms Waugh.
"Create a safe space to have an open conversation. It's important not to shame … but share your needs, frustrations, fears and longing.
"Both partners need to be willing to explore their needs and identify the patterns."
She says some couples may benefit from moving away from "strict ideas" of what sex should be and discussing other ways to be intimate.
"Explore what sex means to each partner to find the connection."
She says couples can introduce novelty back into the relationship by visiting a sex shop or going on date nights, for example.
Ms Baker recommends couples be selective when choosing a time to talk about their sex life.
"Not right in the middle of an argument," she says as an example. "Perhaps after dinner, when the kids have gone to bed."
For women struggling with the mental load, Ms Waugh says men may be able to take on more of the workload.
"A woman is more likely to rekindle desire when she feels heard and unburdened."
If conversations are going nowhere, Ms Waugh recommends seeking support through a professional, which may include a couple's counsellor, sexologist or psychosexual therapist.
Whereas men, she says, are "pretty happy having sex with their long-term partners for nine or 12 years without reporting boredom".
Women crave novelty and excitement in the bedroom, says Ms Waugh, and the burden of mental load doesn't help to increase their sexual interest, either.
'Sex that's not interesting enough'
Esther Perel, a psychotherapist who has spent years studying intimacy and monogamy, has been quoted as saying while men's sexual desire in long-term relationships declines gradually over the years, women's "plummets".
"It's always been translated as, 'Well, that's because women care less about sex', rather than 'It's because women care less about the sex they can have in their committed relationships, which is often not interesting enough for them.'"
One study from 2012 found for women only, lack of interest in sex was higher among those in a relationship of more than one year in duration. Research from 2018 found the longer the duration of the relationship, the more relationship quality could influence sexual desire in women.
And while a 2023 study found sexual boredom to be more common for men in heterosexual long-term relationships, they still had high sexual desire for their partner overall, whereas women's desire for their partner declined as their boredom increased.
Ms Waugh says without "effort or novelty", women's sexual desire can wane over time.
The mental load
In addition to the role monotony plays in this picture, researchers are increasingly looking at how the mental load factors into it.
A study from Swinburne University of Technology in 2022 found that growing inequity over the course of a relationship was often at the root.
Women are largely responsible for the "invisible and visible" work in the home, says Coby Baker, a sexologist in Melbourne/Naarm and south-west Victoria.
"Women, generally speaking, take on more things like doing the kids' school lunches, pick-up and drop-off, thinking about the mother-in-law's birthday present.
"Sex just becomes another thing on the to-do list."
In relationships where household and caring duties are divided more equally, she says women are "more physically and emotionally available for sex".
Having to parent a partner, rather than being able to nurture an emotional connection, can also kill sex drive, says Ms Baker.
More broadly, she says the predictability of day-to-day life means the excitement of that early spark in the relationship fades.
This is especially true for women, who are more likely to experience responsive desire (sexual desire that arises in response to stimulation or arousal, rather than spontaneously).
Women 'putting up' with it
Ms Baker says while some women experiencing a lack of desire or sexual dissatisfaction may choose to end or open the relationship, or even have an affair, the more common outcome is "putting up with bad sex".
"They give men sex because they are tired of being nagged for it. Then they start to become resentful."
Ms Waugh says many women aren't taught to prioritise their own pleasure, and instead treat sex as something they give rather than get to enjoy.
And they often want to change things, but aren't sure how to approach it.
"They don't want to be unhappy. They want more. They want a partner that understands them and their needs."
A couple's problem
Ms Baker says women should remember low desire isn't something that needs to be "fixed".
The Swinburne University research mentioned earlier found that while relationship inequities may have affected dyadic desire (the sexual desire one feels for another), they didn't significantly impact solo desire, which is individual feelings.
"This suggests women's low desire isn't an internal sexual problem to be treated with mindfulness and jade eggs, but rather one that needs effort from both partners," the authors wrote.
Many couples do find their way back when this issue is met with curiosity instead of criticism, says Ms Waugh.
"Create a safe space to have an open conversation. It's important not to shame … but share your needs, frustrations, fears and longing.
"Both partners need to be willing to explore their needs and identify the patterns."
She says some couples may benefit from moving away from "strict ideas" of what sex should be and discussing other ways to be intimate.
"Explore what sex means to each partner to find the connection."
She says couples can introduce novelty back into the relationship by visiting a sex shop or going on date nights, for example.
Ms Baker recommends couples be selective when choosing a time to talk about their sex life.
"Not right in the middle of an argument," she says as an example. "Perhaps after dinner, when the kids have gone to bed."
For women struggling with the mental load, Ms Waugh says men may be able to take on more of the workload.
"A woman is more likely to rekindle desire when she feels heard and unburdened."
If conversations are going nowhere, Ms Waugh recommends seeking support through a professional, which may include a couple's counsellor, sexologist or psychosexual therapist.
