Prenatal “Shocks” and Birth Outcomes

Birth weight is often used as a rough gauge for the quality of the prenatal environment. A newborn who weighs 2500g or less (about 5.5 pounds) is considered to be “low birth weight” (LBW). At the individual level, weight alone is an imperfect measure because of confounders such as gestational length (it’s axiomatic that the less time spent in the womb, the less time there is to grow). However, at the population level, if average birth weight fluctuates, then it is an indication that something in the environment probably has changed.

Sometimes, stressful changes can be low-intensity and chronic; at other times, they can be abrupt and dramatic. Biologists, psychologists, and bioanthropologists might call these changes “stressors” or “insults.” Economists might use the term “shocks.” They’re both getting at the same idea: to what extent can harmful environmental factors affect growth and health outcomes? 

In the case of a natural disaster, the harm done can be substantial. Florencia Torche (2011) found that rates of LBW increased following the 2005 Tarapaca earthquake in northern Chile. Despite the magnitude of the earthquake (7.9 on the Richter scale), the amount of destruction was relatively limited: eleven people died, and 0.035% of the population had to temporarily relocate to shelters. This was attributed to the low population density of the region as well as Chilean preparedness and building codes to withstand earthquakes. Although the damage was not as severe as it could have been, Torche reasoned that the earthquake likely caused acute maternal stress, which in turn could affect prenatal development. 

Looking at over half a million births, Torche used maternal county of residence as an estimate of the earthquake’s intensity across different trimesters of exposure. She found that mothers who were lived in the most intensely affected regions during the first trimester were the most affected. The probability of LBW increased from 4.7% to 6.5%, while rates of pre-term births also increased from 5.2% to 8.0%. Later periods of gestation were not substantially affected, and for infants who were conceived after the earthquake, the probability of LBW returned to baseline.

Again, these outcomes seemed to result primarily from acute psychological stress stemming from the earthquake. Torche reasoned that – given the relatively low amount of damage to infrastructure – the increases in LBW and pre-term births were unlikely to have resulted from other factors such as malnutrition, infection, stress resulting from deprivation, strenuous workloads, or exposure to environmental toxins. In reality, it’s not possible to control for all of these variables entirely, but overall it seems plausible that maternal psychological stress played a substantial role in birth outcomes.

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Syria, After the War

Conscience cannot stand much violence. Once thoroughly broken down, who is he that can repair the damage?” – Frederick Douglass, “My Bondage and My Freedom” (1855, Chapter XI)

The war in Syria has to end, eventually. However, the tragic reality is that the damage is likely to last for decades.

TOPSHOTS-SYRIA-CONFLICT-DAILY LIFE

Woman and child in Douma, Syria in Dec 2014. (AFP Photo/ Abd Doumany)

Yesterday, The New York Times reported that in the past few days “tens of thousands of civilians” have fled the city of Aleppo as the Syrian military, aided by Russian jets, have tried to reclaim the area. This is only the latest wave of civilians being forcibly displaced by the war. Altogether, the UN estimates that more than half of Syrians have been displaced from their homes at least once. Some of these have crossed into other countries, while the rest remain internally displaced.

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The Biology of Forced Displacement

“Seeking asylum is not illegal under international law and people have a right to be treated humanely and with dignity.”  – UNHCR

We crossed the Mekong to get to Thailand at night, so no one would see us. We had always lived in the mountains (of northern Laos), so we did not know how to swim. When we came to the river, we used anything to help us float – bamboo, bicycle tubes. But at night, it is easy to get lost. Someone in our group said: ‘Remember, if you get lost when you’re going down the river (with the current), don’t panic. Thailand is on your right.’ ”

 

 

Every refugee has a story. The one above was told to me by a Hmong man I met in French Guiana in 2001. I went to learn about the experiences of the people there and how they had adjusted to being resettled half a world away, from Southeast Asia to a French ‘overseas department’ in Amazonia. They were actually doing quite well at the time, living as independent farmers who had been given land by the government years earlier.

Hmong men in French Guiana going hunting by bike.

Hmong men in French Guiana going hunting by bike.

They also retained a good degree of cultural continuity. While most are fluent in French, the majority of the 2,000+ Hmong in the country lived in rural, semi-isolated, ethnically homogenous villages. This gave them a buffer of sorts, allowing them to acculturate on their own terms. As they often put it, they were “free to be their own boss,” free to be Hmong, and most said they were happy with life in French Guiana. This combination of traits – economically self-sufficient, culturally distinct, mostly content, living in a rural overseas department – is not the typical refugee story. In fact, because of that relative uniqueness, the French Guiana Hmong have drawn attention from media outlets such as the BBC and the NY Times.

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Developmental Plasticity and the “Hard-Wired” Problem

“Development is the missing link between genotype and phenotype, a place too often occupied by metaphors in the past … But a strong emphasis on the genome means that environmental influence is systematically ignored. If you begin with DNA and view development as “hard-wired,” you overlook the flexible phenotype and the causes of its variation that are the mainsprings of adaptive evolution.” (Mary Jane West-Eberhard, 2003: 89-90)

“Genes, unlike gods, are conditional. They are exquisitely good at simple if-then logic: if in a certain environment, then develop in a certain way… So here is the first moral of the tale: Don’t be frightened of genes. They are not gods; they are cogs. (Matt Ridley, 2003: 250)

 

Plasticity: actor Christian Bale at two points in time. Same genes, different phenotypes.

Plasticity: actor Christian Bale at two points in time. Same genes, different phenotypes.

In his book The Triple Helix, Richard Lewontin told the story of the molecular biologist and Nobel laureate Sydney Brenner, who – while speaking at a conference – predicted that one day we would be able to “compute” an organism (2002). All we would need are two things: the organism’s full genome and powerful enough computers that were up to the task.

The idea is seductive. Genes are sometimes seen as self-sufficient molecules, almost existing in a vacuum, that contain all the information necessary to code for proteins. From there, it’s not a very big logical leap to think that if you had the genome, you could enter the code in some database, hit “run,” and then watch some digitized version of the organism unfold.

In fact, scientists are doing something much like this for the tiny roundworm C. elegans with the project OpenWorm. Yet even for a relatively simple organism such as this, with only about a thousand cells in total, there are reasons to be cautious. As The Economist warned in its write-up of OpenWorm: “Attempting to simulate everything faithfully would bring even a supercomputer to its knees.” However, this isn’t due solely to the limits of computing power (what if we had a super-duper computer!?). Rather, it’s a matter of how the question is framed.

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Infant Mortality Rates, War & Laos

I finished my dissertation on how the war in Laos was correlated to the physical growth of Hmong refugees in 2004. The general idea was that early stressors, particularly prenatally and in infancy, can have long-term impacts on growth and health. The model I was working with came largely from David Barker’s (and others’) ‘fetal origins hypothesis,’ based on evidence that low birth-weight infants tended to grow up to have higher rates of things like type 2 diabates, coronary heart disease, hypertension, etc. A classmate in graduate school, Stephanie Rutledge, introduced me to Barker’s work and told me that I’d find it really enlightening. I did. Sadly, Barker passed away earlier this year, but his work helped spawn a new direction in research. 

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How War Gets Under Our Skin

beinghuman.org front page

I wrote this piece on BeingHuman.org about how war (and the world in general) gets under our skin. It looks at the Hmong example, as well as examples from a few other wars around the world (the Dutch Hunger Winter, the Biafran famine, and the Khmer Rouge period), and how these experiences get into our bodies. 

 

http://www.beinghuman.org/article/how-world-gets-under-our-skin

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Unbending rigor is the mate of death,
And wielding softness the company of life:
Unbending soldiers get no victories;
The stiffest tree is readiest for the axe.

Tao Te Ching: 76

 

Early in life, our bodies are like unmolded clay, ready to be shaped by our experiences. For some of us, that matching process can create problems. If circumstances change, we could end up poorly adapted to our adult environment. A child born into harsh conditions, though, may have to take that risk in order to make it to adulthood at all.

Inequality, Health Disparities, & Obesity

An October poll of 1,000 likely voters found that Americans are increasingly concerned about income inequality. When asked: “How Big a Problem is Income Inequality in the US?,” the majority (74%) replied that it was either a big problem or somewhat of a problem. Predictably, there were differences in opinion by political ideology, but a majority of liberals (94%), moderates (81%), and conservatives (55%) answered that inequality was at least somewhat problematic. However, as is true of many polls, it was not specified exactly what people found unsettling about it. I suppose there are many reasons that people might find increasing inequality (and climbing rates of poverty) to be troubling, but I wanted to focus here on inequality and health, particularly on obesity.

First, what do we mean by poverty? I remember watching an interview on PBS with the economist Jeffrey Sachs years ago (transcript here – thank you, Google), where he distinguished between two types of poverty. The first was an extreme form, which he called the type of “poverty that kills.” The other type was more of a poverty of inconvenience or jealousy. I don’t want to over-interpret Sachs’ meaning. It was a passing phrase in an interview from ten years ago, and his primary focus was on alleviating the extreme poverty faced by more than a billion people in the world living on $1 per day (see Sachs 2005). Elsewhere, Sachs has lamented that the media have ignored poverty in the United States at a time when “the U.S. has the greatest income inequality, highest per capita prison population and worst health conditions of all high-income countries.” His credentials in fighting poverty are unassailable. But I cite the old interview here because I think his descriptions (‘poverty that kills’ vs. ‘poverty of jealousy’) might resonate with many people today, and not necessarily in a good way.

Extreme poverty: scavenging at a garbage dump in Phnom Penh (abcnews)

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