"Several generations of poverty from the Civil War onwards: You had mothers, grandmothers, great grandmothers, whose offspring — I won't say learned — but received signals, anticipating a lean world," Steckel said. "The Civil War is not over. Intergenerational ripples of the Civil War are still with us in the South."
Although it sounds weird, evidence has accrued in population studies and in animal research that stressful prenatal experiences can predispose people to chronic diseases. Several studies have found that people who were in utero during famines are more likely to have cardiovascular disease, diabetes or the erosion of a key cognitive ability than those who were not. People who were exposed to the influenza epidemic of 1918 in early life were more likely to die of cardiovascular disease than people who were not. Studies in animals have shown that prenatal stresses can cause differences in how genes are expressed. The theory goes that those parental experiences shape the offspring's metabolism in a way that responds poorly to a world that is not so strained.
Steckel and his graduate student, Garrett Senney, found evidence that the same thing may have happened in the South, when decades of post-Civil War poverty began to be reversed. Modern-day heart disease deaths were higher in states that experienced a rapid rise out of poverty between 1950 and 1980 — even when controlling for the effects of obesity, smoking and education level.
Steckel and Senney are the first to point out the limitations of their study, which used changes in median income as a crude measure of the stresses and nutrition that people were likely to have experienced in the womb. They weren't able to trace the life trajectories of individual people or families, but instead looked at heart disease deaths among people who were born before the economy improved. They only examined one racial group.
They acknowledge this data is a blunt way to try to answer their complex question. Still, they see the pattern that emerged as a powerful argument for more careful study. If rapid improvements in socioeconomic status carry side effects, it's something doctors could easily ask their patients about when taking a medical history: Did your parents grow up in poverty?
To Kent Thornburg, a professor of medicine at Oregon Health and Science University who is now collaborating with Steckel to see if it is possible to trace just how far this echo of Civil War poverty might last, the data is exciting. Thornburg said that several decades ago, at the dawn of the idea that heart disease could be traced back to what happened in the womb, he was a skeptic. There was evidence that babies with low birth weights later experienced a higher burden of heart disease, but Thornburg didn't think there was any biomedical explanation for why — and birth weight, like socioeconomic status, seemed like a blunt tool to answer the question.
Over the years, that evidence has accrued and an entire field devoted to the developmental origins of health and disease has been born. Thornburg has become a leader in the field, examining how poor maternal nutrition and early life stresses may affect the placenta and the fetus.
"In many cases, including the one in the South, people have suffered malnutrition as well as high levels of chronic toxic stress in their lives when people are faced with poverty," Thornburg said. "Adaptations are made by the baby, but if the baby is faced with a diet of plenty ... where it’s possible to get a lot of fat and sugar, those high-energy diets then are not well-received."
Oliver Rando, a professor of biochemistry at University of Massachusetts Medical School, studies how a father's diet can influence offspring, through laboratory animal studies. He noted that there is uncontroversial evidence from population studies that the diets of parents can affect their children's metabolism in a way that predisposes them to disease. The mystery is how this works, and why — questions Rando and others are beginning to tease out as they reveal the molecular changes that may be at the root of these risks.
But he noted that socioeconomic status — the measure used in the new study — was so broad that it could be difficult to disentangle the influence of prenatal experience from the many other factors that influence health.
Steckel and Senney think their work could have profound implications for revealing a counterintuitive downside of going from rags to riches.
"It makes sense if my mother eats really well and if I'm born and I drop into poverty, there's a negative shock," Senney said. "The big picture of our work is the opposite: If I start in a bad state and have a huge positive shock, there are still negative consequences. The consequences are different."
Steckel is not afraid to wade into ideas that most think are off the beaten track. His early work examined historical height records, using the data to try and understand the standard of living of people during various times in history. He says it was hard to get his grants funded and his work published, initially, and he doesn't mind plunging into an area that will likely raise some eyebrows — both in economics and medicine.
He isn't arguing that lifestyle and genetics do not play an important role in disease. Indeed, the new analysis shows that smoking rates and obesity are major risk factors, too. But Steckel argues that early life effects are fundamental and overlooked by social scientists, and that it is time to bridge the gap between the two worlds. This leads to perhaps the most surprising sentence in their paper:
"The placenta acts as if it contains a small 'biological econometrician' who forecasts the environment for the developing fetus and accordingly tailors the organs such as the heart, kidneys and pancreas to promote survival at least through the age of reproduction."
More from Wonkblog: