In 1860, the average age of a European or American girl’s first menstrual cycle (or menarche) was 16 years old. In 1980, the age dropped to about 13.7 years old. Today, the average age of a girl’s first menstrual cycle is 12.43 years, although the sight of 10 year-olds who look like 14 year-olds is not uncommon. A New England Journal of Medicine study directly conveys secular trends in girls’ age of menarche, particularly the increasingly younger ages of menarche in first world countries, a trend parallel to the rise in nutrition, obesity, and specific types of cancer such as breast cancer. On the opposite side of the spectrum, girls’ ages of menarche in developing countries that often suffer from malnutrition and strenuous physical labor are higher, around 15 years of age.
So, it is not entirely a bad thing that the age of girls’ first periods (or on a grander scale, the onset of puberty) has gotten earlier. From a biological and survival perspective, this means that girls are fertile earlier, can reproduce earlier, and therefore can ensure the continuation of the human race. However, this perspective is rather obsolete in a modern world where population control and environmental conservation have become pressing issues.
While the earlier age of menarche and puberty can be seen as a sign of more nourishment over the decades, it has also become more strongly linked with unhealthily high body mass index and obesity. In a Pediatrics study, Dr. Frank M. Biro found that African-American girls started getting breasts just before they turned nine, and for white girls, the average age was about nine and a half—a few months earlier than in the 1990s. He concluded that breast sizes were consistent with temporal changes in BMI and that BMI was a stronger predictor of early puberty than race or ethnicity.
But why exactly are early periods so worrisome? One of the most obvious reasons could be pulled from a high school health class textbook: the body and mind development do not keep up with each other. A child might have the body of a budding adult while his or her mind may still lack mature, critical decision-making skills. This mismatched development might lead to girls having low self-esteem, succumbing to peer pressure, and using drugs or having sex earlier.
Another reason for concern is breast cancer. The rate of breast cancer among women is one out of eight, a number that also seems to be a symptom or effect of our modernizing world. A main risk factor for breast cancer is exposure to estrogen, the hormone which stimulates breast cell division. The earlier a girl begins her first menstrual cycle and undergoes puberty, the longer she will be exposed to estrogen throughout her lifetime. Consistent with the reasoning, a pooled analysis of data using 117 studies found that breast cancer risk increased by 5% for every year younger a woman was when she had her first menstrual cycle.
Female bodies and health implications are undeniably changing with our modernizing society, and some implications give good reason to consider them risk factors. The data linking breast cancer and early periods is rather convincing, but it’s important to take other factors into account and not establish a causation effect too quickly. Ultimately though, a girl can have an early period and still be completely healthy with proper nutrition and exercise. On the flip side, a high school sophomore girl shouldn’t be freaked out if she has not gotten her period.
Cover image courtesy of Shutterstock.
comments