teristics. But once researchers have
developed a more practical way to
measure levels of key proteins
involved in the disease, such differ-
ences could be crucial for accurate
diagnoses, Morris says. Brain scans
can detect tau as well as amyloid
beta—another protein that builds up
in the brains of Alzheimer’s suffer-
ers—but the scans are expensive
and not widely available.
The study found no racial differ-
ence in amyloid levels. Afri-
can-American study participants,
though, had a much lower concen-
tration of tangled clumps of the tau
protein, whether or not they had
dementia. The research looked at
1,255 people—some with Alzhei-
mer’s, some cognitively normal—in-
cluding 173 African-Americans.
The study also found that a variant
of a gene called APOE4, which
confers a high risk of Alzheimer’s in
whites, seemed to be less of a peril
for African-Americans. The latter
tended to have much lower tau levels
if they had the APOE4 variant,
suggesting they suffered less
neurological damage because of the
lesser tau exposure. “The mechanism
may be different in AfrIcan-Ameri-
cans than it is in whites,” Morris says.
Alzheimer’s occurs more often in
black Americans, even if the gene
itself is more benign. Morris says
some blacks may be more likely to
wait until advanced stages of the
disease before seeking medical care.
Other research has suggested
APOE4 provides some protection
against infectious diseases including
malaria, and that the gene is more
common in people whose ancestors
came to the U.S. from tropical
climates where those diseases are
more frequent. Among the Saint
Louis study participants, African-
Americans were just as likely to
have the APOE4 gene as were
Caucasians. But in an earlier study
in Atlanta that also looked at tau
and APOE4, black Americans with
dementia were far more likely to
carry APOE4. African-Americans had
lower levels of tau in both studies.
Tau may accumulate differently in
the brains of African-Americans
because of genetic differences
between the races or because of
the chronic stress of racism and oth-
er factors, notes William Hu, a
neurologist and researcher at Emory
University School of Medicine who
led the earlier study. It is unclear
what the mechanism might be, butAfrican-Americans are known to
have a different response to inflam-
mation than whites, he says. “There
may be a different inflammatory
response that would lead to a
different tau-based response.”
In the new research, tau was
measured in cerebrospinal fluid.
Patients also underwent PET brain
scans to measure amyloid buildup,
MRIs to gauge brain volume, genetic
testing for APOE4 status and other
clinical evaluations. “This is a critically
important study as we move toward
the goal of individualized medicine,”
Hu says.
If lower levels of the tau protein
mean a patient has less Alzhei-
mer’s-related damage to the brain, as
research suggests, African-Ameri-
cans with these relatively low levels
might be more responsive to drugs
that are being developed to attack
amyloid, Hu says. Amyloid tends to
aggregate before tau in the disease
process.
These regional research efforts,
Hu says, should spur a nationwide
study that examines how race
affects various aspects of disease
progression. Such a study, he adds,
should be designed with a propor-
tionally higher number of blackparticipants to make the findings
statistically valid. The race a person
checks off on a form is a crude
biological measure. Eventually, he
says, this type of study will define
groups by genetic makeup rather
than self-described race to account
for the many individuals of mixed
heritage.
Morris also urges more investiga-
tion to understand how Alzheimer’s
acts in diverse groups of people. “I
hope this publication will stimulate
the need for our research efforts to
become more welcoming to people
of color,” he says, “and not settle for
enrolling individuals who are fairly
easy to enroll: upper-class whites.”
Keith Fargo, the director of
scientific programs and outreach for
the Alzheimer’s Association, says
the study is a reminder that measur-
ing protein levels in the brain and
other advances should not be used
yet in physicians’ offices until they
are better understood. “It’s a good
idea to continue to measure these
biomarkers in all different kinds of
people—and not get too far ahead of
ourselves in terms of clinical prac-
tice,” he says.
—Karen WeintraubN EWS