Tall people live longer, earn more, and are better educated. Or rather, tallness is associated with these factors—if you put a short person in elevator shoes, they won’t magically gain a few extra years of life. The association comes partly because when a country develops, its education levels improve, along with nutrition and health. Tallness, then, could be considered a symptom of a well-developed country.
A new study published in eLife Science looks at the trends in average human height over the last century, reanalyzing almost 1,500 population studies from 1896 to 1996. These studies covered 18.6 million people in 200 countries and allowed the researchers to tease out all kinds of trends and associations.
For example, the biggest changes in height during the century happened to South Korean women (8 inches taller) and to Iranian men (6.5 inches taller). The least change occurred in sub-Saharan Africa and South Asia. And the tallest people of all are Netherlander men born in the last 25 years of the century—they average six-feet tall. And the height difference between the tallest and shortest people in the world was the same at the beginning and end of the century: around 7.9 inches.
After gathering the numbers, the researchers set about interpreting them. Some of the height differential between different countries comes from genetics, but most is chalked up to other causes.
Height is important because tall people really are healthier. They are less likely to suffer heart disease or strokes, and taller women are less likely to experience complications during pregnancy and child birth. There is one downside, though, to being so tall that you have to kneel down to put your hands in your pockets: taller people are more at risk from some kinds of cancers.
Closer to home, the U.S. used to be one of the tallest nations 100 years ago but now falls behind Europe. This is in part thanks to a large growth period earlier in the century, which plateaued and let other countries catch up. The result is that U.S. women, for example, used to be the fourth tallest in the world, but dropped to the 42nd tallest, while actually gaining an inch in average height (5’3" to 5’4"). U.S. men grew three inches (5’7" to 5’10"), but dropped through the rankings from third tallest to 37th tallest. Other countries, like Spain, continue to grow, although the current financial crisis might halt that trend, because Spanish babies are being born smaller.
One place the U.S. still leads in in body mass index (BMI). While they’re not growing much taller, Americans are getting much rounder. "Height has increased less than the worldwide median, while BMI has increased a great deal," says the study, somewhat euphemistically.
The available data is better for men than women, thanks in some part to the detailed records of military conscripts and volunteers. That said, the available data on women shows that their height increase has made Japanese and South Korean women among the longest-lived in the world, with the first-longest and fourth-longest life-expectancy, respectively.
Current figures show that China and Thailand are now racing to catch up, with men and women both increasing in height faster than elsewhere.
The study reaches no straightforward causal conclusion—the factors are too varied for that. But it does seem clear that getting good nutrition as children plays a large part, and this is also a clear indicator of the development level of a country. Viewed like this, the low placing of the U.S. really sticks out, and shows that it’s not just the quantity of nutrition that counts. If that were true, the U.S. would be a country of superhuman basketball players, not a nation of short, round basketball viewers.
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