London - Two in five older women are unhappy with their sex lives, the survey found.
About 38.8 percent 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 percent 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 percent 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.