Posted by Nowa Omoigui

In Reply to: Hypertension In Nigeria and in African American posted by Nccny

Dear Consul:

It is not 'eurocentric arrogance' on the part of the
encyclopedia. What it states is reflected in standard
textbooks and research materials - including books
dedicated to Heart Disease in Blacks to which people
like Prof. Elijah Saunders and Prof. Akinkugbe
contributed.

But one can always invoke inadequate or inaccurate
data capture as a factor in any epidemiologic study.
So your concerns are valid and should lead to a more
detailed research effort to clarify the matter. If new
observations are documented, that may open the door
to new research to establish what has changed in the
more recent post colonial era in Africa. Has the oil
boom (or doom), for example, with all of its effects
on rural-urban migration, diet, exercise, class
differences and lifestyle stress in 'richer' African
countries like Nigeria had any adverse effects? Are
those of us in the modern african elite who have
imbibed western civilization and all of its creature
comforts and competitive stresses bucking the
traditional trend?

Traditionally (and crudely speaking) there has been an
observed increasing gradient in the prevalence of
hypertension from Africa to the Caribbean to the US.
Within Africa itself there is also a gradient from
rural to urban - with rural folk being said to be at
lower risk than urban "westernized" folk - who tend to
consume more salt and live stressful lives.

One classic example of this was illustrated by the Luo
migrant study in Kenya. The Luo are a rural ethnic
group that used to thrive mainly on goat milk. When
Luo were recruited into the British colonial army, and
deployed (ie migrated) to urban centers where they
acquired a different life style, the average blood
pressure of the group increased. When they were
demobilized and returned to their rural life style
blood pressure profiles virtually normalized within 6
months.

Coming to a more tantalizing theory of why
hypertension among US blacks is worse than Caribbean
blacks which in turn is worse than "African" blacks,
it is said that it resulted from a selection process
related to survival in the era of slavery.

Consider this. Picture all those slaves who were
herded together above and below deck in horrendous
circumstances during the various voyages from Africa
to the new world - denied water and food for the most
part to save stocks.

Who was likely to survive such a journey? Answer:
Those with an inherent tendency to retain salt and
hold on to their body water to avoid dying from
dehydration. This highly selected subgroup became the
ancestors of the modern African-American - who has a
much greater tendency to retain salt than his or her
counterparts in the Caribbean or Africa itself (on
average).

Finally, a word of caution. Hypertension is a
multifactorial disease. No matter how biologically
plausible the slave ship salt hypothesis may be, there
are numerous poorly understood genetic and
environmental interactions that are factors in the
disease and many unanswered questions remain about the
aggressive course it tends to take in African
Americans.

Regards,

NAO

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