Now, thanks to a long-term study of women's reproductive cycles begun in the 1930s and a $2 million grant from the National Institutes of Health, Penn State researchers hope to shed light on the years before women reach menopause and investigate how their health and reproductive histories affect the patterns of change.
"Anything that takes us a step further in identifying the changes leading up to menopause will be very helpful," says Dr. James W. Wood, professor of anthropology in College of the Liberal Arts and senior research scientist in Penn State's Population Research Institute.
The researchers plan to collect first morning urine samples from approximately 150 women ages 35 to 60 for six months of each year during the five-year project. The samples will be analyzed for the metabolic remains of four hormones linked with the monthly female reproductive cycle -- estrogen, progesterone, luteinizing hormone and follicle-stimulating hormone.
"Collecting 28,000 samples per year over five years and analyzing them is a daunting prospect," says Kathleen O'Connor, a National Institute of Aging Post-Doctoral Trainee at Penn State's Population Research Institute and research associate in anthropology. "But understanding the variations and being able to model these changes could benefit many women. For example, in guiding women and their physicians in making choices about hormone replacement therapy."
"This research would not be possible without the Tremin Trust," says Wood. "The dedication of these women is amazing." The Tremin Trust, begun at the University of Minnesota by Alan Treloar in 1934, enrolled university women in a long-term reproductive study. The first cohort of women was recruited in the 1930s and the second in the 1960s and 1970s. Both cohorts have kept continual calendars indicating the starting and ending dates of their monthly periods. Annual health surveys are done each year and include information on births, abortions, miscarriages, surgery, marriage, divorce and stressful events as well as general health and birth control information. In 1984, the trust moved to the University of Utah under the oversight of Ann Voda in the School of Nursing.
"These women are dedicated," says Dr. Phyllis Mansfield, professor of women's studies and health education. "When funding for the study decreased, the participating subjects sometimes included checks with the surveys to support the project."
Mansfield worked with Voda on the Midlife Women's Health Study which used Tremin Trust data and participants.
"Only the Trust data can supply this kind of long-term data on women's reproductive health," says Dr. Darryl Holman, postdoctoral fellow in Penn State's Population Research Institute. "There is no other long-term study of this type."
More women today are living into their 90s, spending the same or more years post-menopausal than fertile. The health implications of the hormone patterns of perimenopause for women at these post menopausal ages has not been explored.
Women are born with all the ovarian follicles -- egg precursors -- they will ever have. Each month a number of egg precursors begin to grow, but normally most die off, leaving one egg per cycle to ovulate. As women age, they have fewer and fewer follicles left until no follicles remain.
The standard medical definition of menopause is 12 continuous months without menstrual bleeding. Because the follicles control the cycle of hormones that lead to preparation of the uterus for egg implantation and eventually to menstruation when no egg is fertilized, menopause occurs when all the follicles are used up. It is typical for women to experience variable cycles, including very long cycles when approaching menopause. The patterns of perimenopause vary among women in ways that are poorly understood.
"Some women experience irregularity for only a short time before they stop menstruating forever," says Wood. "Others experience irregularity and missed periods for many years before experiencing menopause. Still others believe they are post menopausal and begin to menstruate again."
Little is known about how life histories affect the patterns leading to menopause. Smoking is thought to lower the age of menopause, while the effects of hormones from birth control pills and replacement therapy are unknown.
"Much of what we know about women's reproductive cycles came from the first cohort of the Tremin Trust," says Mansfield, a faculty member in both Colleges of Health and Human Development and the Liberal Arts. "Information on perimenopause, menopause and post menopause, which is of great interest to women today, will come from the second cohort of this long term project."
The Penn State researchers are working with researchers from Georgetown University and Princeton University on this project.
EDITOR: Dr. Wood is at 814-865-1936 or
jww3@psu.edu by email by email.
Dr. Mansfield is at 814-863-0356 or pkm@psu.edu" by email.
Dr. O'Connor is at 814-863-7743 or oconnor@pop.psu.edu
by email.
Dr. Holman is at 814-865-1231 or holman@pop.psu.edu
by email.
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