Wednesday, February 13, 2008

Aggressive breast cancer among African Americans in the Chesapeake Bay...can ancestry in Africa explain this?

This new paper in AJHB (abstract below) suggests a framework with which to understand why breast cancer rates in the Chesapeake Bay area are so high compared to the rest of the US, and why they are particularly aggressive among African Americans. They ask: What was the African ancestral source of the African Americans who currently live there, and provide some evidence that it was groups from around the Bight Of Bonny.
first about ethnic disparities in the US:
On a national scale, European American women have a higher incidence of breast cancer than African American women after the age of 35 but African American women have a higher incidence before age 35 and are more likely to die from breast cancer at every age. This disparity is reportedly widening (Jatoi et al., 2005).
What's interesting about the Chesapeake bay:
In the Chesapeake Bay region, comprising Maryland, Virginia, Delaware, and the District of Columbia, (Fig. 1), breast cancer is exceptionally high.
What they hypothesize:
Thus, it is hypothesized that the composition of the founding populations, particularly among local African American women in the Chesapeake Bay region, may explain, in part, the Chesapeake Bay foci for this disease pattern.
What is special about the Chesapeake Bay with respect to African ethnic groups.
The Chesapeake Bay retains the highest concentration in the United States of descendants of enslaved Africans from the Bight of Bonny coastal and hinterlands catchment region. Nationally, this local clustering of Bight of Bonny descendants can be compared with much smaller proportions of Bight of Bonny-region Africans brought to the Carolina Coast (7%) and the Mississippi Delta regions (6%) (Jackson, 1997)
They discuss some of the potential environmental confounders such as "contaminated
local fish and other Bay products", as well as others.
and, a concluding hypothesis from their summary:
We hypothesize that the composition of the founding populations, particularly among local African Americans in the Chesapeake Bay region may play an important role in predisposing many current regional microethnic groups to breast cancer. Ancestral links to the Bight of Bonny may be particularly important in understanding US breast cancer differentials, both between and among African Americans.
I think that they make a valiant effort to figure out, or at least think about why, Chesapeake Bay Americans and particularly the African Americans in that area are at such high risk of aggressive breast cancer by relating it to the ancestral composition of the Africans who were brought there. They discuss this at the "microethnic" scale as they call it, discuss the historical evidence, and narrow it down to the Bight of Bonny. It's definitely a hypothesis-generating kind of study, calling for a more detailed genetic examination of African groups.

Ancestral links of Chesapeake Bay region African Americans to specific Bight of Bonny (West Africa) microethnic groups and increased frequency of aggressive breast cancer in both regions
Fatimah L. C. Jackson
American Journal of Human Biology Volume 20, Issue 2, 2008.
Abstract The high frequency of aggressive, early onset, and highly fatal breast cancer among Chesapeake Bay region African Americans suggests that there may be a contributing ancestral component. This study identifies the region's founding African, European, and Native American Indian populations using ethnogenetic layering and identifies the microethnic substructure of each founding continental aggregate. The largest component (38%) of the enslaved Africans brought to the Chesapeake Bay originally came from the coastal and hinterlands of the Bight of Bonny, a region with very high rates of aggressive, early onset breast cancer. Ethnogenetic layering is applied a second time to reveal the microethnic groups of the Bight of Bonny hinterlands with historical links to the Chesapeake Bay region. These analyses identify the specific microethnic groups within this region of Africa that may be the sources of relevant polymorphisms contributing to the etiology of aggressive breast cancer in the Chesapeake Bay. This report suggests a historical link between specific African microethnic groups and a US health disparity.


jwag13 said...

Still a big mystery WHY though right?

Yann Klimentidis said...

for sure

price per head said...

Disparities exist between African-American and European-American women in the incidence and nature of breast cancer. African-American women are more often diagnosed with breast cancer at an earlier age and with more aggressive disease, characterized by higher grade and negative estrogen and progesterone receptor status. Recent findings reveal specific gene expression patterns associated with the more aggressive breast cancers observed in African-American women. An overview of the current literature about racial differences in breast cancer prompts questions for future research to elucidate causes for the apparent disparities in tumor biology.

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