We say that children grow up too fast. New science suggests this axiom, sadly, is all too true.
Researchers, led by Frank M. Biro, MD from Cincinnati Children’s Hospital recently completed a four-year study of puberty in girls. The study, published in Pediatrics, followed over 1,200 girls of all races from Cincinnati, San Francisco and New York City. Dr. Biro and his associates tracked when these girls entered stage 2 of pubescent breast development. This is the stage where physical changes begin to manifest in girls’ breasts.
The data shows that, on average, girls today are entering puberty younger than they were even 10 years ago. Race has always played a deciding factor in puberty. Black girls, who enter puberty earlier than other races, begin developing at age 8.8. This number has stayed static through the years. According to Biro’s data, white girls today enter puberty sooner than they have in the past, at 9.7 years. The trend to younger puberty is much the same in Hispanics and Asians.
The biggest factor leading to early onset of Stage 2 breast development in girls is Body Mass Index (BMI). BMI takes into account factors such as age, height, weight, muscle density and others, to provide a numerical measure of fitness. High BMI numbers generally correlate to increased weight and a larger percentage of body fat. Girls with higher BMI enter puberty sooner than girls with lower BMI.
While researchers aren’t yet certain what aspect of a higher BMI leads to an early onset of puberty, the data strongly echoes the importance of physical fitness in children and adolescents. Yes, children are growing up too fast, but shooing them outside for an hour each day can help keep them young.
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