Editor’s note: Pending an FDA decision, 23andMe no longer offers new customers access to health reports referred to in this post. Customers who purchased prior to November 22, 2013 will still be able to see their health reports, but those who purchased after that time will not. Those customers will have access to ancestry information as well as access to their uninterpreted raw data.
Two of the biggest physical milestones in a woman’s life are menarche (pronounced “MEN-ar-kee”), the first menstrual period in girls, and menopause, when menstruation stops and female reproductive hormones slow. These milestones are universal and mark the beginning and end of a woman’s reproductive cycle.
Research suggests that the age at which menarche and menopause occur is about 50% influenced by genetics and 50% determined by non-genetic factors, though there is also some evidence that menarche may be more strongly influenced by genetics than menopause.
Menarche marks an important rite of passage because it signals the possibility of fertility although ovulatory cycles don’t typically begin for a few more years. Many cultures have traditionally recognized this time in a girl’s life through celebrations, ceremonies, or other rituals. In Japan, “red rice” (sekihan) is customarily served for a girl’s first period and Navajo Native Americans have celebrated this time with Kinaalda, which translates as “puberty ceremony”. During this four-day ritual girls run footraces to exhibit their strength and are initiated into womanhood with a ceremony. Such rituals are less commonly observed today.
Age at Menarche
Studies have found that nearly all girls in the US menstruate by the age of 14, with the median age around 12 and one-half years. These numbers haven’t really changed over the last few decades, although girls today may show signs of puberty (breast growth and pubic hair display) at a younger age. The average age of menarche can vary by ethnicity, though, and African-American girls typically start menstruating before girls of European descent.
In addition to genetics, timing of menarche is influenced by environmental factors such as nutritional status and exercise. Early menarche has been associated with increased risk for breast cancer and endometrial cancer, a connection that many theorize is related to the body’s exposure to estrogen, a female reproductive hormone.
Age at Menopause
Menopause typically occurs between the ages of 40 and 60 with the average age around 51 years. A woman knows that she’s entering menopause if she experiences hot flashes, difficulty sleeping, irregular libido, and mood swings, symptoms that can sometimes be alleviated by hormone replacement therapy. A small fraction of women experience “early menopause” in their 30s, which can cause fertility problems and may also be influenced by genetic factors.
Research on Menarche and Menopause
Although some genome-wide association studies have been carried out to identify genetic factors for age at menarche, much less is known about the genetics underlying age at menopause. These important milestones are known to be influenced by ancestral origin, though more research is needed to identify genetic factors in non-European populations.
It’s National Women’s Health Week. Stay tuned for more posts about big health issues facing women today including autoimmune diseases, infertility and breast cancer.