Black American Women Are Getting Shorter, Study Says
Tuesday, January 6, 2009
On average, black American women are getting shorter.
That's the conclusion reached by John Komlos, an economist who researches the relationship between standards of living and human health and body size. His study, which has not yet been published, analyzes data recently released by the National Health and Nutrition Examination Survey (NHANES), part of the U.S. Centers for Disease Control and Prevention.
It's a surprising development, since Americans in general have gotten taller from one generation to the next. For any population group in the developed world to get shorter "is more or less unprecedented in modern times, except in dire circumstances" such as war or famine, said Komlos, a professor at the University of Munich.
According to the NHANES data, black women who were born in the United States around 1980 are on average a little shorter than 5-foot-4 today. Those born in the mid-1960s are on average a little more than half an inch taller.
White women born around 1980, meanwhile, are more than three-fourths of an inch taller than black women of the same age. Komlos's study found white men to be a little bit taller on average than black men, but not to a statistically significant extent.
Exactly what these figures mean is not certain. Komlos sees a relationship between the decline in height and obesity, a national epidemic that has hit African American women particularly hard. According to a 2007 report by the National Center for Health Statistics, 23.8 percent of black girls ages 12 to 19 are overweight, compared with 14.6 percent of white girls. The report did not specifically cite obesity statistics for teens, but it said 51.6 percent of black women ages 20 to 74 are considered obese, compared with 31.5 percent of white women of the same age. Obesity, Komlos said, results in youngsters "maxing out" their growth earlier.
Alan Rogol, a professor of clinical pediatrics at the University of Virginia at Charlottesville and Riley Hospital for Children in Indianapolis, explained it this way: Obesity causes an apparent acceleration of the onset of puberty in young people. In the case of young women, "the female hormone estrogen is what leads to closure of the ends of long bones, where you grow from," Rogol said. "If that is done more quickly on average, you are at risk for being . . . smaller as an adult."
Komlos's study follows one he published two years ago, showing that the growth rate of the U.S. population had slowed since the end of World War II, at the same time as Western Europeans' growth rates were accelerating. For this study, he and fellow researchers analyzed NHANES data from 1976-80, 1988-94 and 1999-2006; they analyzed people from 20 to 45 years old, "ages at which height is relatively stable at the individual level for both men and women."
Genetics has a significant role in determining a person's ultimate height. But nutrition and lifestyle also have an impact, as does access to health care, Komlos writes in his study. "The American diet needs a bailout, like the auto industry," Komlos said. "It's connected with the whole economic conception of overconsumption." His study found the height differential for black women more noticeable at the lower end of the socioeconomic spectrum, where people's diets tend to be less healthful and where health care is less accessible.
Komlos's findings are interesting, Rogol said, but should be considered nothing more than an indicator of other health issues.
"Being 5 foot 5 inches versus 5 foot 6 inches is not a major health issue," Rogol said. "There are many more complications of obesity than losing half an inch of height. . . . I would worry more about cardiovascular and estrogen-related problems and cancer than I would about adult height."