Women approaching menopause, however, can relax as the study, one of the first to accurately document what happens to a woman's sexual functioning during menopause, also identified factors that help protect against this sexual dysfunction.
The findings are part of the University of Melbourne's Women's Midlife Health Project being conducted by the University's Office for Gender and Health that has been following a large group of Melbourne women for over ten years.
"This is the first study worldwide to follow a population-based group of women for more than ten years and record symptoms of menopause as well as physical measurements that include blood samples to record hormone levels, bone density and skin fold thickness," says the project's Chief Investigator, Professor Lorraine Dennerstein.
"The study is also one of the few to have a validated sexuality questionnaire. This allows us to measure changes in women's sexual function and associate it with changes in hormone levels," she says.
The study found women going through the menopausal transition experienced a decline in sexual interest, a decrease in arousal and in the frequency of sexual activity, and an increase in vaginal dryness and pain during intercourse.
These dramatic changes were linked to a plunge in levels of the hormone estradiol. Other hormones, including the male-dominant hormones testosterone and androgen, were investigated but only estradiol, produced by the ovary, could be linked to this deterioration in sexual functioning specifically associated with the natural menopause. The findings are published in the April Supplement of Fertility Sterility.
In an invited lecture to the triennial International Menopause Society conference in Berlin on 14 June, Professor Dennerstein will announce from yet to be published data that the use of estrogen-containing hormone replacement therapy (HRT) is protective against the decline of sexual functioning in menopausal women.
The data also details the relevant importance of various factors on sexual response. Relationship factors appear to have the greatest effect, having the capability of overwhelming hormonal changes.
"Factors like a woman's level of sexual responsiveness before menopause, changes in partner status (for example gaining or losing a partner), and a woman's feelings for her partner can override hormonal effects. Hormonal effects are most likely to be noted by women in long-term, stable relationships," says Professor Dennerstein.
"Many of the women in our study also report qualitative changes in sexual function. They say their relationship with their partner has changed to be more companionable," she says.
With funding from the Alzheimer's Association (USA), the Melbourne Women's Midlife Health Project is now investigating if declining hormones levels also affect women's memory.
Professor Victor Henderson, a visiting academic from the University of Arkansas for Medical Sciences, USA, is coordinating the research.
"Memory is important in its own right, but memory loss is also sometimes an early marker for Alzheimer's disease," he says.
"We want to see if there are any links between midlife hormonal changes and memory loss and if estrogen therapy can play a role in helping stave off or prevent memory deterioration."
The Melbourne Women's Midlife Health Project began in 1991 and since then has identified those symptoms that can truly be associated with the menopausal transition rather than, for example, ageing. They have also documented the changes occurring in hormone levels and how hormonal and other factors interact to affect risk factors for cardiovascular disease, osteoporosis and quality of life.
The findings are being used to provide women and health care professionals with accurate information about what are normal menopausal experiences, to assist government and international bodies with policy and health care practices and to provide guidance for future clinical trials and research.