Puberty is an uncomfortable phase of our life that we cannot deny. Between voice changes, hair growth, and acne, the change can be overwhelming for teens. This is the stage in which hormonal changes produce physiological changes in the body, such as the development of sexual organs and accelerated growth. However, for many children, the average age of puberty has been decreasing during decades.
Some girls today start developing breasts as early as 6 or 7 years old. Something that has puzzled scientists, who are already investigating whether these changes are affected by obesity, stress or chemical substances.
The studies. During the last three decades, Studies from Europe and the United States have shown a trend toward the earlier onset of puberty in girls, with a greater change in the age of breast development—often the first sign of puberty—compared to the first menstruation (menarche). Recent studies have confirmed that, in dozens of countries, the age at which girls start puberty has fallen by about three months per decade since 1970.
In children, it has also been observed similiar trend. A 2019 study from Trusted Source examined the height and growth of more than 4,000 children in Sweden between 1947 and 1996. They used growth velocity, or the timing of a pubescent growth spurt, as a cue. For every decade that passed, the children reached their maximum height speed 1.5 months earlier.
The tendency. For decades, medical textbooks have defined the stages of puberty using the so-called Tanner scale, which was based on observations of girls and boys between 1949 and 1971 in England. The scale states that normal puberty begins at age 8 or later for girls and at age 9 or later for boys.
But in 1999, Paul Kaplowitz, professor of pediatrics at Children’s National Hospital in Washington, defended that the age limit for normal puberty should be lowered to 7 years for white girls and 6 for black girls, according to their studies.
Why? Nobody knows. Many complex factors affect the onset of puberty. Genetics are thought to explain 50-75% of the variation, with the rest attributed to lifestyle factors such as nutrition, general health, psychosocial stress, perinatal factors, body composition body and environmental factors, such as endocrine disruptors.
Obesity? Indeed, the trend toward earlier puberty is often seen in connection with the parallel epidemic of obesity among adolescents. As indicated in this report from The New York Timesobesity has been associated with early menstruation in girls since the 1970s. Since then, in A lot of studies it has been shown that overweight girls tend to start menstruating earlier than girls of average weight. In a study conducted over decadeschildhood obesity was related to earlier menstruation: each standard deviation above the mean weight in childhood was associated with a double probability of having the rule before the age of 12 years.
And in 2021, British researchers They discovered that leptin, a hormone released by fat cells that limits hunger, acted on a part of the brain that also regulated sexual development.
Chemical substances? Early studies on endocrine disruptors as a cause of early onset of puberty have shed light on the matter. some recent have shown that exposure to such chemicals in the fetal and neonatal period is also relevant to the timing of puberty.
In a 2009 study, girls who developed breasts at younger ages had the highest levels of phthalates in their urine, substances used to make plastics last longer and found in everything from vinyl flooring to food packaging. They are substances called “endocrine disruptors”, which can affect the behavior of hormones and that in last decades they have become ubiquitous in the environment.
Stress? Similarly, psychosocial stress preceding or during puberty can cause a delay in menarche, while accelerated puberty has been described in girls who experience such stress in early postnatal life or as infants. There is less research in the field on boys, and therefore little is known about what affects the timing of the onset of puberty.
Negative consequences. Early puberty, particularly in girls, has been associated with adverse health effects in adults. Observations indicate that early menarche is associated with increased mortality, as well as increased risk of breast cancer, cardiovascular disease, and mental illness. In addition, early puberty has been shown to be associated with more frequent and prolonged adolescent-related risk behaviors.
In addition, girls who reach puberty prematurely have a higher risk of suffering from depression, anxiety, drug addiction and other psychological problems compared to their peers who reach puberty later.
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