by Kirsten Hartil
This post is a modified version of a paper submitted for the Multiculture and Diversity Issues course of Einstein’s MPH Program.
The Centers for Disease Control and Prevention estimates that in the U.S. every year 25,000 infants die before their first birthday. These rates are lower than most low- and middle-income countries. Sierra Leone, for example had an infant mortality rate of 117 deaths per 1,000 in 2012. Still, according to Save the Children’s 14th annual State of the World’s Mothers report, 50 percent more newborns die within their first 24 hours in the U.S. compared to all other industrialized countries combined.
Congenital malformations, pre-term birth or low birth weight, sudden infant death syndrome (SIDS), and maternal complications and injuries (e.g., suffocation) are the major causes of infant mortality in the U.S., accounting for 57% of all infant deaths in the United States in 2010.
Large racial disparities exist in rates of infant mortality. African Americans have significantly higher rates compared to Whites and Hispanics (Figure 1). Infant mortality is 2.3 times higher in African Americans compared to non-Hispanic Whites. In 2009, African American infants were almost four times as likely to die due to complications related to low birth weight and their mortality rate from SIDS was twice that of non-Hispanic White infants, the rate of low birth weight was much higher among infants born to African Americans than infants born to mothers of other racial/ethnic groups. Even after correcting for maternal education the infant mortality rate for African Americans is greater than that of non-Hispanic Whites1.
Why do African American women have a higher probability of having premature, low birth weight babies?
During Introduction to Public Health we watched the PBS series, Unnatural Causes. In one episode Dr. Michael Lu, an Ob/Gyn at UCLA, discussed one theory: the role of racism. He suggests that the chronic stresses of everyday exposure to racism impacts the physiology of the mother and this negatively impacts the fetus putting it at increased risk of death.
In Multiculture and Diversity Issues we discussed multiple forms of racism: structural and institutionalized racism is responsible for differential access to resources such as employment, housing, health care (see the Institute of Medicine, 2002 report, “Unequal Treatment”) and education (60 years after Brown versus the Board of Education, NYC has one of the most racially segregated school systems in the country; African American school children are more likely to be suspended or expelled from public schools than their white peers); and increased exposure to risk factors (such as unnecessary contact with the criminal justice system (for instance, the four times higher incarceration rates of African Americans compared to Whites for marijuana possession.)
A second form, is unconscious racism, the implicit biases a person holds (see The Daily Beast rebuttal of the White Privilege essay written by a white male Princeton student) and microaggressions—“brief and commonplace daily verbal or behavioral indignities, whether intentional or unintentional, that communicate hostile, derogatory, or negative racial slights and insults that potentially have a harmful or unpleasant psychological impact on the target person or group”2. Think about the “I, Too, Am” campaigns, started at Harvard and replicated at NYU and Oxford.
Our Life’s Course Shapes Our Health
Maternal stress is a risk factor for low birth weight and other unfavorable birth outcomes, independent of poverty and poor nutrition 3,4. James W. Collins and Richard J. David at Northwestern University have proposed that the cumulative stress created in women’s bodies after decades of dealing with racism is responsible for the large share of the disparities found in birth outcomes of African American families.
In Social and Behavioral Dimensions of Public Health we covered the life-course perspective and the concept of allostatic load: “the cumulative wear and tear, physiologically, on the body as a result of chronic exposure to the stress response” 5. They attempt to explain how life experiences (including poverty, social support and environmental, genetic and psychosocial factors) shape health across a person’s lifetime and potentially across generations. Latendresse (2009) discusses how stress and allostatic load may explain poor perinatal outcomes resulting from maternal stress 6.
The stress of racism is increasingly becoming recognized as a key determinant of health and epidemiological studies show associations between self-reported racism and poor health 7. Of course association does not imply causation but a growing body of literature suggests that discrimination is associated with worse mental and physical health including anxiety and depression (for reviews see 7-9).
The physiological stress response, responsible for the “fight or flight” response, involves the release of hormones (including cortisol, corticotrophin-releasing hormone and adrenocorticotropin) by the hypothalamic-pituitary-adrenal axis and the release of catecholamines by the autonomic nervous system 10. A causal effect of maternal stress on birth outcomes has been demonstrated in animal models, supporting the epidemiological associations. Adult offspring of mothers stressed in a variety of ways, exhibit physiological changes and altered brain function and behavior (Choe et al, 2011; Chung et al, 2005; Son et al 2006, 2007, Mueller & Bale, 2008; Weinstock, 2008). The mechanism involves changes in the hypothalamic pituitary adrenal axis (HPA) and elevated cortisol levels and can result in long term effects in the offspring.
The Long Term Consequences
For low birth weight infants that survive, their reduced fetal growth has impacts on their physical and mental health. Low birth weight is associated with increased risk of cardiovascular disease and metabolic syndrome, cognitive development, attention-deficit hyperactivity disorder and depression. Additionally low birth weight is associated with lower educational attainment and future income and an increased probability of having a low birth weight infant 11-13.
It should be noted that stress is linked with an increase in unhealthy behaviors such as poor diet, smoking and substance abuse, all of which are risk factors for low birth weight. Collins et al., found that even when including these variables in a logistic model, perceived discrimination still increased the odds of having a very low birth weight child 14.
Whatever the precise mechanisms, African American women and women living in poverty are subjected to unnecessary stress which harms their babies and puts their children at risk of failing to develop their full potential, perpetuating a vicious cycle of poverty.
Kirsten received her PhD in clinical biochemistry from Cambridge University, where she studied the developmental origins of health and disease, an area of research she continued when she joined Dr. Maureen Charron’s lab as a postdoc. In 2010 she joined Dr. Irwin Kurland’s lab in the Diabetes Research Center, and used metabolomics and stable isotopes to study metabolic flexibility. In 2012 she decided it was time for a career change and was accepted into the MPH program at Einstein. She hopes to transition into a career working to prevent obesity in people rather than study obesity in mice. She contends, “as scientists we have a responsibility to communicate research in a way that is both understandable and accurate. Being interesting and fun is a bonus. Some people are better at this than others. Contributing to the EJBM blog is my way of sharing stories that I think are important while improving my own writing skills.”
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