SEATTLE, Wash. -- Women in developing countries who reach menopause early may be experiencing the same condition as anorexics and runners, rather than the natural progression of aging, according to a Penn State researcher.
"Rural women in developing countries tend to experience menopause about eight years earlier than in developed countries," says Dr. Darryl Holman, postdoctoral fellow in Penn State's Population Research Institute. "On average, American women experience menopause at about 51 years old, while rural Bangladeshi women, for example, are about 43 years old at menopause."
Holman proposes two possible explanations. Rural women in developing countries naturally enter menopause earlier, or the apparent earlier age of menopause is a stress-related shutdown of the ovarian cycling. He notes that urban women in developing countries tend to have a later age of menopause.
"By the time women in developing countries reach their early 40s, they have had repeated pregnancies, breast-fed for most of their adult lives and have a relatively high disease load," Holman told attendees today (Feb. 15) at the annual meeting of the American Association for the Advancement of Science in Seattle. "These women have very low body mass, and their amenorrhea -- absence of menstruation -- may be due to the same things that affect runners and anorexics."
Menopause naturally occurs when a woman's ovaries have no follicles left that can develop to release fertile eggs. Because women have a set number of follicles that begin to undergo atresia -- degeneration and resorption -- in the fetus, when all the follicles are used up, they enter menopause.
Holman does not think that rural women in developing countries are born with fewer follicles, which would account for an earlier menopause. Rather, he thinks that these women are undergoing a variety of stresses that combined, stop the normal cycle of hormones. Runners and anorexics frequently experience amenorrhea due to a combination of low body weight and stress.
"Menopause is characterized biochemically by high levels of two hormones, luteinizing hormone (LH) and follicle stimulating hormone (FSH) and low levels of estrogen," says Holman. "Amenorrhea is characterized by low levels of LH and FSH but may have normal levels of estrogen."
Holman is looking at hormone data and reports of menses and breast-feeding for about 500 women from a survey of 3,000 Bangladeshi women who were asked if they were menopausal. These women supplied twice weekly questionnaires and morning urine samples for a year.
"Some women who said they were menopausal, had actually experienced a menstrual period within the year," says Holman. "Preliminary analysis of the hormones in the samples seem to indicate that some of the women are actually experiencing amenorrhea, rather than menopause."
Because of their low body weight, disease load, the stress of nursing and general under nutrition, their bodies stopped cycling. However, just as the follicles in their ovaries experienced atresia before they entered puberty, the follicles continue to degenerate even though they are not menstruating. Eventually, all their follicles will be exhausted, and they will enter true, biological menopause.
Holman notes that improved nutrition, better medical care and fewer pregnancies will all occur as these countries develop, and the age at menopause will increase approaching that of the United States.
"One consideration of this phenomenon is that women will need to practice birth control later in their lives," says Holman.