One of the alarming trends in the US, as well as other foreign nations around the globe, is that girls are maturing earlier. In contemporary times, it is common for young girls to start the beginning stages of puberty (hair growth, breast development, etc.) at 7 or 8 years old, a record breaking age compared to past centuries. While the menarche (first period) still does not show itself till about twelve years of age, this is still an unprecedented early age when looking at the trend of first menstruation over the 1800’s and the 1900’s.
First noticing this trend over 140 years ago, researchers began documenting the age of the first menstruation. In 1860, the average age of menarche was occurring at 16.6 years old, showing a steep decline in the following decades, marking it as 14.6 years in 1920 and 13.2 years in 1950. While this trend seems to finally have leveled off since the 80’s where the last recorded and most accurate age is 12.5 years old, the rate at which the first stages of puberty is observed is still rapidly declining.
Boys, like girls, are also seeing the emergence of puberty (facial hair, growth spurts, etc) at younger and younger ages, but the trend toward full blown puberty at an earlier age is not as rapid or as pronounced as it is the female sex.
Another epidemic affecting more and more young girls, is the problem of precocious puberty – or premature puberty. Scientifically, this is defined by breast development accompanied by a growth spurt in girls younger than the age of 8. Due to the decreasing trend in the age of girls at the start of puberty, there is a lot of debate over what age is actually too young (considering the norm) and should be defined as “precocious”.
There is also argument over what actually constitutes the onset of puberty. Dr. Lawrence Silverman, a pediatric endocrinologist at Goryeb Children’s Hospital in Morristown, New Jersey argues that sometimes precocious puberty is wrongly diagnosed, stating “The appearance of acne and pubic hair is common even in infants and toddlers. It goes away. We need to be careful about how we identify the true onset of puberty.” In most cases of true precocious puberty, the body will eventually correct itself, causing the process to slow down and stall, but not before causing menstruation in the premature, often emotionally unprepared girl.
Despite the overall decline in age of the onset of puberty, the data does differ vastly when considering variables like race. In the US, for example, African-American and Hispanic girls tend to reach puberty earlier than their white counterparts by 1-1.5 years. The mean age of breast development in African-American girls in the US is 8.9 years old compared to the much older 10.5 years that is the mean age for breast development in Caucasian girls. While the cause of this is unclear, there are many, interacting factors affecting the situation.
While everything from economic reasons to climatic change to genes has been cited as part of the cause in the decline of age at the onset of puberty, none of these can explain the overall reduction, rather than just individual cases.
One of the most widely held beliefs is that improved nutrition in modern times has caused bigger and heavier children than in the past, allowing for normal growth. Another probable cause and one with the most evidentiary proof is the rising epidemic of obesity globally. At the annual conference of the American Academy of Pediatrics in Orlando, Florida, in 2001, pediatric endocrinologist Dr. Paul Kaplowitz presented a study he conducted that included girls from the ages of 6 to 9 and helped discover a link between body fat and the timing of puberty.
Beyond loosely linked evidence and slight correlations, the scientific community is still perplexed and unable to explain the reduction of age in the onset of puberty and the rapid increase of precocious puberty, leaving it a hot topic for future studies.