Mamas on Bedrest: Genetics and Stress add to Racial and Ethnic Disparities in Preterm Births

March 31st, 2014


More and more research is indicating that not only genetics, but stress and racial and ethnic health care disparities are responsible for not only the rise in many chronic diseases, but also for the high rate of preterm births-especially in African Americans and Latinas.

Research in a relatively new field of genetics called epigenetics is finding that our environment-chemicals and other toxins-as well as increased stress are responsible in part (if not entirely) for the high rates of preterm labor in the United States. The United States has the highest rates of preterm labor and prematurity in the industrialized world, and rates are highest amongst African Americans and Latinas. While genetics and cultural evolution are often blamed for the increases, researchers have come to the conclusion that the rise in various chronic diseases, the rise in preterm births and the health care disparities that exist between the races simply cannot be explained by genetics alone.

Michael K. Skinner, a professor at Washington State University and the founding director of the Center for Reproductive Biology in the School of Biological Sciences is a researcher in epigenetics.

“Genetics is part of the story, an important part of the human story,” says Skinner. “But epigenetics, that is the other half of the equation.”

Epigenetics is the study of molecular changes including DNA methylation, the technical term for the way that our environments and experiences can subtly alter our gene activity. The genes turned “on” and turned “off” when we are exposed to certain chemicals, man-made poisons, or—perhaps most surprisingly—emotional experiences, can make us more or less susceptible to particular health problems.

Elizabeth Corwin, dean of research at Emory University’s Woodruff School of Nursing, and her team of researchers closely tracked more than 100 women during the last three months of their pregnancies. They found that women of all races and ethnicities who were poor during their pregnancies were more likely to suffer from chronic stress, a biologically detectable and quantifiable condition. But what was more alarming was that middle-class black women and all Latinas except for those who were immigrants were also more likely to suffer from chronic stress and they had higher rates of chronic stress and more pronounced negative side effects. According to Corwin and her colleagues,

Black women and Latinas across socioeconomic categories—those with and without insurance, college degrees, and access to the best food and information—were significantly more likely to test positive for elevated levels of stress hormones and conditions than those hormones can set in motion. This made the women more likely to deliver their children early. Chronic stress, the team determined, is the reason approximately 30,000 more African-American babies are born prematurely each year than any other group.

Corwin and her team also found that chronic stress is entirely different from day to day “annoyances”. ‘Chronis stress is created by some combination of financial stress, relationships stress, community pressures, and experiences like racism—actual and perceived.’ (paraphrased from original statement to add clarity)

What is even more alarming is the fact that stress experienced by one generation is actually perceived and affecting offspring 2, 3 and 4 generations out. Skinner and his colleagues have proven exposure to certain chemicals can affect the genes likely to activate in the sperm and egg cells of mice four generations down the line. His findings have been repeated in other large animals, been published in peer-reviewed scientific journals, and have significant implications for humans.

Both Corwin and Skinner know that their research will fall on many a “deaf ear” and opponents will balk at the implication that racism, classism and other forms of subtle and not so subtle discrimination are affecting the health of people and up to 4 generations removed. However, their research is clearly making the case.  Four to five generations ago, the ancestors of today’s middle-class African-Americans were likely to have been enslaved in brutal physical and emotional conditions. Large numbers of Mexican nationals came to the U.S. beginning in the 1940s to work in the agricultural industry were regularly exposed to chemicals used in farming. Some workers were even sprayed with pesticides upon arrival. Descendants of both ethnic groups suffer some of the worst health outcomes across the board. On top of that history, informal social codes, land prices, and land-use laws often leave poor communities closest to local waste facilities, mines where workers rake coal from the earth, or coastlines dotted with refineries and those residents who live in proximity to those areas at increased risk for disease.

Ana Penman-Aguilar is the associate director for science in the Office of Minority Health and Health Equity at the Centers for Disease Control and Prevention. She states that the CDC is very interested in this work as it has far reaching implications for our nation as a whole. “The Health of the Nation as a whole cannot be improved without making significant gains in Minority Health”, she says. And adds that the CDC is also a focusing on the social determinants of disease, “the way income, diet, neighborhood—basically how and where we all live, learn, work, and play—can drive health disparities.”

The study of epigenetics is a relatively new field, but its results are nothing short of astounding! While opponents may want to ignore the cultural and societal implications of this research, we can no longer claim ignorance of the role discrimination is playing in our society, especially as it pertains to the health of certain ethnic groups of people. If our interpersonal behavior is effecting people 2, 3 and 4 generations down the line, we as a society have no choice-if we wish to survive-but to address our societal and cultural biases and meet the needs of ALL our citizens.


Epigenetics: The Controversial Science Behind Racial and Ethnic Health Disparities.  The National Journal


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