Women get bored of having sex with their partner after just a year together, a new study suggests.
They are four times more likely to not care about having a steamy night of passion than those in shorter relationships.
But the same trend does not exist for men. Their sexual interest does not fade over time, researchers claim.
The 'important' findings, made by Southampton University researchers, were based on answers from 11,508 participants.
Women who have been in relationships for longer than a year are four times more likely to not care about having a steamy night of passion than those in shorter flings
The National Survey of Sexual Attitudes and Lifestyles is the largest study of sexual habits in the UK. This was the third one undertaken.
What else did the study find?
Overall, 34 per cent of women said they lacked interest in sex, compared with 15 per cent of men, the study published in BMJ Open found.
The survey showed that both men and women were at risk of being put off sex by past experiences of forced sex.
Other passion-killers included poor mental and physical health or having recently had a sexually transmitted infection.
For women, having had three or more partners in a year was linked to a decline in libido alongside having children under five.
HAVE SEX TO PREVENT WRINKLES
Having sex at least once a week slows aging in women - even if they do not enjoy being intimate, research found in July.
Being active between the sheets increases the length of women's telomeres, University of California, San Francisco, scientists found.
These 'cap' the end of DNA strands, with longer lengths being associated with slower aging, longer lifespans and improved overall health.
Women's telomeres lengthen with regular love making regardless of whether they are sexually satisfied in their relationship, the research added.
Researchers believe sex may aid aging in women by dampening stress and boosting their immune system.
They were also put off regularly making love if they had different sexual preferences to that of their partner, the results showed.
What did the researchers say?
Lead author Professor Cynthia Graham said: 'Our findings show us the importance of the relational context in understanding low sexual interest in both men and women.
'For women in particular, the quality and length of relationship and communication with their partners are important in their experience of sexual interest.
'It highlights the need to assess and - if necessary - treat sexual interest problems in a holistic and relationship, as well as gender-specific, way.'
Who was involved in the study?
Of the participants, 6,669 were women and 4,839 were men. They all had at least one sexual partner in the past 12 months.
Women were slightly more likely to find it easy to talk about sex than men, the research also found.
It comes after a Kinsey Institute study last month revealed how often people are meant to have sex - depending on their age.
Those aged between 18 and 29 should be having sex an average of 112 times a year. Between the ages of 30 and 39, it drops to 86 times annually, researchers said.
And sexual activity tails off even further for 40 to 49-year-olds who have half the amount of sex of their 20-something counterparts, making love 69 times a year.
The mid-life sex drive crisis
Two in five older women are unhappy with their sex lives, the survey found.
Some 38.8 per cent of 55 to 64-year-olds said they had lacked interest in sex for at least the last three months.
The figure was only slightly lower for the 45 to 54 age group, of whom 37.9 per cent had lost interest.
However, the survey suggested women become more content with their sex lives as they get older. Among the 65 to 74 age group, only 34.2 per cent said they lacked interest in sex.
One possible explanation is the menopause, which hits women around the age of 51 and causes a loss of libido, as well as other often debilitating symptoms.
Experts also say that middle age women are under more stress than other groups, with the competing pressures of family life and work.
Being a mum kills passion
Having children ruins your sex drive – but only if you are a woman.
The survey found women with one or more children were 50 per cent more likely to be unhappy with their sex lives than those who had none. But men who had children were no less happy with their love lives.
Survey participants were asked whether they had lacked interest in sex for the last three months or more. Many parents have warned that having children ruined their sex lives as they are inclined to interrupt at the crucial moment.
Women sometimes find sex painful after childbirth or find that they are too exhausted for passion in between waking up with the baby.
Relationship experts say couples should make time for each other and try to be intimate, even if they do not feel like sex straight away.