Reduced estrogen levels are the main cause of vaginal dryness. Estrogen, a female hormone, helps keep vaginal tissue healthy by maintaining a normal vaginal acidity level. Acidity creates a natural defense against vaginal and urinary tract infections. But when your estrogen levels decrease, so does this natural defense and the amount of vaginal lubrication. Decreased estrogen amounts can lead to a thinner, less elastic and more fragile vaginal lining. 
 

“Scientists have documented that some of the physical effects of diminished estrogen levels-- vaginal dryness and pain during intercourse—may affect a woman's sexual activity. This study is the first to examine a range of social and psychological factors, as well as health issues, in a representative sample of healthy women and to define how they relate to sexual functioning as women end their reproductive years,” commented Dr. Marcia Ory, Chief, Social Science Research on Aging, Behavioral and Social Research, National Institute on Aging. This research was part of the NIH-supported Study of Women's Health Across the Nation (SWAN), a large-scale national effort to examine the health of women in their 40's and 50's, with special emphasis on the physical, psychological, and social changes that take place at mid-life. 

Although the investigators found that reaching menopause influenced women's beliefs about aging and interest in sex, it did not contribute to how often the women had sexual intercourse, whether they were happy with their sexual relationship, whether they had problems having orgasms, or whether they experienced pain during or after intercourse. 

If diminished levels of estrogen contributed to lessened sexual interest and activity, there should be a direct relationship between estrogen levels and sexual functioning. The researchers found that lower estrogen levels were only related to pain with intercourse. Therefore, hormonal levels, health and social changes associated with aging, and the mental and emotional effects of being recently menopausal probably work together to create any changes in a woman's sexual interest that occur at the time of menopause. Longer-term studies could determine whether reduced estrogen production does affect a woman's sexual functioning as she gets farther from menopause.