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by Wei Perng, PhD


As discussed in an earlier blog post, height can convey a lot about health. Attained stature is a sensitive marker of early life circumstance and is generally positively associated with better health outcomes. This phenomenon has been observed in epidemiological studies and I’ve even heard it referenced by my non-scientist parents. As with many Asian immigrants of their generation, my parents came to the U.S. not only because it is the land of opportunity, but also because it is home to organic food, a clean environment, and better health. Despite their longing for family and Taiwanese culture, they stand firm in their decision to emigrate because in addition to both my brother and I being healthy, educated, and gainfully employed, my brother is 6’4’’ - a whopping ten inches taller than most of our extended family. When my relatives exclaim how tall my brother is, my dad (5’8”) and mom (5’2”) beam and say: “If we had stayed in Taiwan, he would probably be several inches shorter.”
News flash: Americans are not just getting wider – we are also getting shorter! I attended a lecture in graduate school by economic historian John Komlos, who presented some graphs illustrating the shrinking heights of Americans over the last few decades. This surprised me, as I knew that between the colonial times through the middle of the 20th century, America was the tallest nation in the world. Yet, the U.S. population is currently at the shorter end of the height distribution among industrialized countries. Further, the average height of some European countries like the Netherlands is still increasing. This discrepancy is disturbing, especially considering that physical stature is an indicator of biological well-being. What might explain these downwards height trends in the U.S.?

Social inequality & poverty. Komlos speculated that the shrinking height of Americans could be attributable to social inequalities. We typically see a direct relationship between a country’s per capita income and height of its people. Yet, according to our gross domestic product (GDP), which is higher than that of any other major economy, Americans are actually getting richer at the national level. What gives? Although those of highest socioeconomic status do tend to be taller, there is still a large underclass pulling the average down in the stature charts. We still have 9 million people with no job (5.5% of the U.S. population), 42 million with no health insurance (13.4%), and 45 million living below the poverty line (14.5%). Further, as discussed in a 2013 New York Times article, our middle class - which comprises the bulk of the American population - is not immune to the risk of unemployment and depressed wages, both of which are indicators of suboptimal socioeconomic conditions that could negatively affect height growth. Komlos also surmised that the U.S. GDP per capita is high because the Americans who are employed work many more hours than their European counterparts, leading to lack of quality family time, fewer home-cooked meals, and possibly even neglected children. While these qualitative indicators of the social environment are difficult to quantify, it is certainly possible that they have a measurable impact on early growth and attained stature.

Poor diet & obesity.  It’s likely no coincidence that our fast-food culture developed in the second half of the 20th century, concomitantly with the obesity epidemic and height stagnation. The problems of poor diet and our growing waistlines go hand-in-hand with social inequality: the poorest Americans tend to consume more processed foods and fast food. Kids in the U.S. consume more meals outside the home and more fast food high in fat and low in essential micronutrients than do European children. The high-fat, high-sugar Western diet is directly associated with obesity, which may lead to shorter attained height. Some pediatricians believe that obesity causes earlier onset of puberty. In young women, estrogen leads to the closure of growth plates at the ends of long bones, which are responsible for linear growth. If that occurs earlier, then one is at risk for being shorter as an adult.

Anecdotes. Other explanations I came across while researching this topic were that we may have reached our “full genetic potential for height” and that these trends are simply natural fluctuations of the leveling-off process. Others believe that the answer to the puzzle is immigration. As more Latin/Mexican Americans and Asians enter the U.S., they lower the average height. This makes sense, especially since immigrant populations tend to live in poorer socioeconomic conditions. However, this possibility has been dismissed, since at least one study included data only on native-born Americans who spoke English at home, excluding persons of Asian and Hispanic descent.

Should we be worried? A few inches difference in height is likely not a major health issue, but America’s relative shortness does suggest that something is awry with our way of life – whether it be the dual burden of unemployment in the face of excessive work hours, or our increasing BMIs in the face of poor nutrition.

 


Comments

Susan Laubach
08/06/2015 10:04am

Amazing! I think I am too distracted and saddened by America's growing obesity to ever notice we are shrinking in stature. I don't suppose eating more ice cream for calcium for our bones will help!?

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Molly zimmerer
08/07/2015 12:09pm

Lets keep those growth plates growing and drink more milk! So glad you and your brother both stand out on many ways!

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