American Journal of Epidemiology
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Vol. 174, No. 3
Advance Access publication:
June 1, 2011
Practice of Epidemiology
Inclusion of African Americans in Genetic Studies: What Is the Barrier?
Sarah M. Hartz, Eric O. Johnson, Nancy L. Saccone, Dorothy Hatsukami, Naomi Breslau,
and Laura J. Bierut*
* Correspondence to Dr. Laura J. Bierut, Department of Psychiatry, School of Medicine, Washington University, Campus Box 8134,
660 South Euclid Avenue, St. Louis, MO 63110 (e-mail: email@example.com).
Initially submitted July 15, 2010; accepted for publication February 28, 2011.
To facilitate an increase in the amount of data on minority subjects collected for genetic databases, the authors
attempted to clarify barriers to African-American participation in genetic studies. They randomly sampled 78,072
subjectsfrom the community (MissouriFamilyRegistry,2002–2007).Of these, 28,658participated in a telephone
screening interview, 3,179 were eligible to participate in the genetic study, and 1,919 participated in the genetic
study. Response rates were examined in relation to the proportion of subjects in the area who were African-
American according to US Census 2000 zip code demographic data. Compared with zip codes with fewer
than 5% African Americans (average ¼ 2% African-American), zip codes with at least 60% African Americans
(average ¼ 87% African-American) had higher proportions of subjects with an incorrect address or telephone
number but lower proportions of subjects who did not answer the telephone and subjects who refused the
telephone interview (P < 0.0001). Based on reported race from the telephone screening, 71% of eligible African
Americans and 57% of eligible European Americans participated in the genetic study (P < 0.0001). The results
of this study suggest that increasing the number of African Americans in genetic databases may be achieved
by increasing efforts to locate and contact them.
African Americans; consumer participation; data collection; genetic association studies; genetics; minority groups
The majority of genetic studies are constructed with sam-
plesofhomogeneous populationsofEuropean descent. There
are 2 primary explanations for low numbers of ethnic minor-
ities in genetic databases. In part, the number of minority
subjects mirrors the difference in population prevalence. Sec-
ondly, investigators may specifically exclude non-European
Americans in order to increase statistical power to find ge-
netic associations by creating a more uniform genetic and
environmental background (1, 2). However, as the field of
genetics diversifies into personalized medicine, it is essential
that multiple ethnic groups be studied. It cannot be assumed
that findings based on European Americans apply to other
ethnic groups. Moreover, different ancestral groups can be
more informative than a single population, because of varia-
tions in linkage disequilibrium leading to improved localiza-
tion of potentially functional polymorphisms (3).
There is a vast body of literature describing distrust of
medical research in minority populations (4). Much of this
literature has focused on African-American communities,
often attributing the distrust to the historical abuse of African
Americans in the Tuskegee Syphilis Study (5–10). Genetic
studies are thought to have a particular potential for discrim-
ination because of the collection of genetic information. For
this reason, multiple studies have examined African-
American participation specifically in genetic research pro-
tocols (11–17). In these studies, subjects were recruited
from a medical screening or medical study, and recruitment
into the genetic protocol was evaluated by computing the
proportion of participants in the medical screening who also
participated in the genetic portion of the study. In all pub-
lished studies, African-American subjects were statistically
less likely than European Americans to participate in the
genetic component of the study (11–17), although partici-
pation rates of both African Americans and European Amer-
icans were still relatively high.
Although published participation rates in genetic studies
are lower among African Americans than among European
Americans, there is no evidence that distrust of research
leads to decreased participation rates in other medical re-
search. A recent meta-analysis of nongenetic medical stud-
ies found similar participation rates in minority subjects as
compared with European-American subjects (8). A similar
336Am J Epidemiol. 2011;174(3):336–344
study of survey research supported this finding: Once con-
tacted, ethnic minorities were more likely to participate
(18). The combination of lower African-American partici-
pation rates in genetic studies with similar participation
rates in nongenetic medical studies suggests that African
Americans view participation in genetic research differently
than participation in surveys and other medical research.
To better understand differences in participation in ge-
netic studies between African Americans and European
Americans, we used a large, population-based sample col-
lected for a genetic study of nicotine dependence. This study
design allowed us to examine 3 distinct steps in recruitment:
establishment of initial contact, participation in screening,
and recruitment into the genetic study (including a blood
draw). Subjects were randomly selected fromthe community,
contacted by telephone for a screening, invited to participate
in the genetic study, and then brought in to the study center to
undergo an extensive interview and blood draw for genetic
analysis. Prior to telephone screening, at which point ethnic-
ity was self-defined, subjects’ ethnicities were unknown
but were estimated on a population level with US Census
2000 data (http://www.census.gov/main/www/cen2000.html).
By comparing ethnicity and demographic characteristics
at each stage of recruitment and ascertainment, we
evaluated differences between European-American and
African-American participation at each step.
MATERIALS AND METHODS
As part of the Collaborative Study on the Genetics
of Nicotine Dependence (19, 20), 78,072 subjects aged
25–44 years were randomly selected from the Missouri
Family Registry between 2002 and 2007. The Missouri
Family Registry includes all persons with a driver’s
license or state identification card in St. Louis City,
St. Louis County, and St. Charles County, Missouri. Vari-
ables for which data were available were gender, date of
birth, and address. Zip codes with higher proportions of
African Americans were oversampled to increase the
numbers of African Americans in the study. After random
selection, subjects were sent a letter and then contacted
by phone for a brief screening interview. If determined
to be eligible for the study of nicotine dependence, the
subject was invited to participate in a face-to-face inter-
view and a blood draw for genetic analysis. The research
protocol was approved by the Washington University
institutional review board.
In order to prepare the potential subjects for our telephone
call, a letter was sent describing the study and informing them
that they would be called for screening purposes (Figure 1).
The same standard letter was mailed to all subjects.
Subjects not screened
Because many subjects were unavailable or unwilling
to complete the telephone screening, we evaluated whether
the various reasons for lack of contact were related to
ethnicity. Of the 78,072 subjects who were selected as
the target population, 28,658 (37%) were screened by
phone. Of the remaining subjects, we tracked the reason
that the subject had not been screened, including: 1) in-
ability to find the subject because of an incorrect address
(returned letter) and/or a discontinued or inaccurate
phone number; 2) no answer on the telephone after mul-
tiple attempts; and 3) refusal to participate in the tele-
Although we did not know the characteristics (including
ethnicity) of unscreened subjects, we compared the reasons
a subject had not been screened with US Census 2000
demographic characteristics based on the subject’s zip code
(http://factfinder.census.gov). This particular data set was
used because subjects were recruited between 2002 and
2007, and it was the closest census for which data were
available. Because of the ethnic segregation by zip code in
the St. Louis region, we were able to compare subjects from
zip codes with less than 5% African Americans (average ¼
2% African-American) to subjects from zip codes with
at least 60% African Americans (average ¼ 87% African-
American), inferring race based on the zip code. This
allowed us to evaluate reasons for failure to contact potential
subjects by estimated ethnicity.
The telephone interview was designed to determine
medical eligibility for a case-control study of genetic factors
in nicotine dependence (19, 20) and self-identification
as either European-American or African-American. The
interview took, on average, 5 minutes to administer and
consisted of questions regarding nicotine use, family
structure (living parents or siblings), and demographic
factors, including race, age, marital status, employment
status, and health insurance. Eligible subjects were re-
quired to have smoked 100 cigarettes in their lifetime,
to meet the definition of case/control status (a Fagerstro ¨m
Test for Nicotine Dependence (21) score of 0 for con-
trols and ?4 for cases), and to have both a living parent
and a living adult full sibling. The text was not geared
toward a particular ethnic group. An excerpt from a sam-
ple text of the telephone interview follows (see Figure 2,
My name is... and I’m calling from Washington University.
We recently sent you a letter describing our study of smoking.
Did you receive the letter? Yes/no
If yes: Good; as you may recall...
If no or don’t remember: Well, let me tell you a bit about
the study... Washington University received funding from
the National Cancer Institute to do a study on smoking. Would
you be willing to take a few minutes to answer some questions?
If yes: Participation is voluntary, and your answers will be kept
Once eligibility for the genetic study had been determined,
the following sample text for recruitment was read (see
Figure 2, part B).
Inclusion of African Americans in Genetic Studies337
Am J Epidemiol. 2011;174(3):336–344
As we mentioned earlier, this is a family study of smoking,
and the goal of the project is to understand why some people
become addicted to cigarettes and others quit smoking
or never even start to smoke. Your participation in the study
would involve a completely confidential interview that in-
cludes questions about your medical history, use of alcohol
and drugs, your mood and personality, and your family’s
smoking history. This takes approximately 3 hours, and
you will receive $100 for your time. Your answers will
be kept strictly confidential and will not be shared with any-
one outside of our research staff. We also ask that you
provide a blood sample. Are you willing to participate in
This text initiated a discussion about participation in the
study. If a subject decided to participate, an interview was
On-site interview and blood draw
Eligible participants were invited to the in-person inter-
viewandblooddrawforgenetic studies.Prior toparticipation
Introduction letter sent prior to a telephone screening call for a genetic study of nicotine dependence, St. Louis, Missouri, 2002–
338 Hartz et al.
Am J Epidemiol. 2011;174(3):336–344
in the study, the informed consent form was read to the sub-
jects, where the details of the genetic study and the risks of
participation in a genetic study were described in depth (see
Figure 2, part C).
Subjects who participated in the studycompleted a 4-hour
in-person interview and a blood draw for later genetic anal-
ysis. Subjects received $100 in compensation for their time.
The interview included an extensive history on smoking and
substance use in addition to a full psychiatric, medical, and
Zip codes were stratified into 4 groups based on the per-
centage of persons aged 25–44 years who were African-
American: <5%, 5%–<30%, 30%–<60%, and ?60%.
Demographic differences in zip codes between the 4 strata
of African Americans were evaluated using analysis of var-
iance, where each zip code was weighted by the sample size
within the zip code. Proportions of persons living in poverty
and persons with a college degree throughout the sampled
region were calculated using a weighted average of these
levels across the zip codes, weighted by the number of per-
sons sampled in the zip code. Associations between reasons
for lack of contact and proportion of African Americans
in a zip code were evaluated using weighted regression.
Participation rate was defined as the proportion of eligible
subjects who both donated blood and participated in the
face-to-face interview. The v2test was used to statistically
evaluate differences in participation rates between groups.
We attempted to contact 78,072 people, and we con-
ducted telephone interviews with 28,658 (Figure 2). Al-
though the demographic characteristics of the unscreened
subjects were unknown, we tallied the reasons for lack of
contact by zip code and compared these data with the US
Census 2000 demographic data for the zip code (Table 1).
There were 86 zip codes with at least 10 sampled persons,
for a total of 77,886 persons (99.8% of the sampling frame).
We stratified the zip codes by the proportion of African
Americans in the zip code. Compared with zip codes with
less than 5% African Americans (average proportion ¼ 2%
African-American), zip codes with at least 60% African
Americans (average proportion ¼ 87% African-American)
had higher proportions of subjects with an incorrect address
or phone number (51% vs. 39%, P < 0.0001) but lower
proportions of subjects who did not answer the telephone
despite repeated attempts (14% vs.17%, P < 0.0001) and
lower proportions of subjects who refused the telephone
interview; B) offer of study participation; C) signing of the informed consent form prior to participation in the study. Difference in participation rates
between European Americans and African Americans: P < 0.0001.
Selection of participants for a genetic study of nicotine dependence, St. Louis, Missouri, 2002–2007. A) Initiation of the telephone
Inclusion of African Americans in Genetic Studies339
Am J Epidemiol. 2011;174(3):336–344
Characteristics of Zip Codes Sampled for a Genetic Study of Nicotine Dependence, Including Demographic Factors and Reasons for Lack of Screening, St. Louis,
% of African Americans in Zip Code
<5 5–<30 30–<60
No. % (SD)
No. % (SD)
No. % (SD)
No. % (SD)
No. of zip codes441613 13
No. of subjects aged
299,180123,404 21,127 63,139
No. of subjects sampled26,316 13,252 21,12717,191
Average % of African
2 (1)12 (6) 47 (8)87 (9)
% of persons below
4.7 (2.6) 9.7 (5.5) 19 (12)31 (13)
% of college graduates**
31 (19) 29 (18)28 (13) 10 (6)
Annual per capita
28,571 (12,619) 24,093 (8,464)20,629 (5,236)13,015 (3,419)
Participated in telephone
35 (8)37 (4)35 (7) 32 (6)
9 (5) 7 (3)5 (2) 3 (1)
Did not answer
17 (6)16 (2)14 (2) 14 (1)
Incorrect address or
39 (12)39 (7)46 (9) 51 (7)
Abbreviation: SD, standard deviation.
* P < 0.05; **P < 0.0001.
aP value for difference between proportions of African Americans, based on weighted regression.
Hartz et al.
Am J Epidemiol. 2011;174(3):336–344
interview (3% vs. 9%, P < 0.0001). Because the proportion
of African Americans in a zip code is highly correlated with
the other demographic characteristics of the zip code, the
observed associations between proportion African-American
and reasons for failure to contact were confounded by these
demographic characteristics. In particular, the correlation be-
tween the percentage of persons under the poverty level and
the proportion of African Americans in these zip codes was
0.85. Therefore, we were unable to determine whether the
difficulty in contacting these subjects was due to poverty or
To evaluatewhether the subjects participating in the study
represented the general population, we compared some
demographic characteristics of the participating subjects
with those of the sampled region estimated from the US
Census 2000 data. The proportions of subjects living under
the poverty line in our sample were 38% of African Amer-
icans and 16% of European Americans, as compared with
the US Census 2000 rates of 25% of African Americans and
10% of European Americans (for the sampled region). The
proportions of subjects with a college degree in our sample
were 11% of African Americans and 43% of European
Americans, as compared with the US Census 2000 rates
of 18% of African Americans and 30% of European Amer-
icans. Although our sample in the genetic study appears
to have been different from a random sample selected from
the community, it is interesting that the participating sub-
jects had higher rates of poverty and African Americans
had lower proportions of college degrees than the region
overall. This suggests that the recruited sample of African
Americans was not a more selectively advantaged popula-
tion than the sampled region.
The participation rate, calculated by dividing the number
eligible, was significantly lower in European Americans than
in African Americans (57% vs. 71%, P < 0.0001). This
difference was driven by the higher rate of participation
by African-American cases (76% participation) than by
African-American controls (63% participation), although
both of these rates were higher than the European-American
participation rates of 57% in cases and 58% in controls.
The demographic characteristics of the subjects who com-
pleted telephone screening and qualified for the study are
given in Table 2. In both European-American and African-
American populations, subjects with some college education
were more likely to participate than subjects without any col-
lege education (P < 0.001). In European Americans, women
were more likely to participate than men (P < 0.001), and
unemployed subjects were more likely to participate in the
genetic study than employed subjects (P < 0.05). There was
no difference between the younger age group and the older
age group. In African Americans, there were no statistical
differences between participants and nonparticipants in
terms of gender, age, or employment.
Using data collected for a large genetic study of nicotine
dependence, we traced subjects from random selection in
the community through participation in a telephone inter-
view and finally recruitment into the genetic study. This
comprehensive design enabled us to evaluate which steps
posed barriers in the recruitment of African Americans into
genetic studies. First, we found considerable difficulty in
locating subjects who lived in zip codes with higher pro-
portions of African Americans because of changes of ad-
dress or phone number. However, with a correct phone
Dependence, by Ethnicity, St. Louis, Missouri, 2002–2007
Demographic Characteristics of Screened Subjects Who Qualified for a Genetic Study of Nicotine
European AmericansAfrican Americans
% ParticipationNo. % Participation No.
Age group, years
25–34 60 89374*
35–44 561,580 70*
High school diploma or less 54**
Beyond high school61**
Total 572,473 71706
* P < 0.05; **P < 0.001.
aInformation on gender was missing for 1 European American.
bP value for test of difference between participation rates within each ethnic group.
Inclusion of African Americans in Genetic Studies341
Am J Epidemiol. 2011;174(3):336–344
number, these subjects were more likely to answer the
phone and more likely to participate in the telephone in-
terview. Finally, when identified as eligible, African Amer-
icans were more likely to participate in the genetic study
than European Americans. This suggests that the willing-
ness to participate in genetic studies is not a significant
barrier. In contrast, our data suggest that the strongest bar-
rier is the establishment of initial contact. These results are
consistent with findings in nongenetic studies, where locat-
ing minority subjects is the critical barrier to obtaining their
participation (8, 18). This suggests that strategies developed
in medical and survey research would also be effective for
the recruitment of ethnic minorities into genetic studies
(22). In particular, targeting geographic regions (e.g., census
blocks) with a high prevalence of minority households or
otherwise oversampling minorities from a known sampling
frame will increase contact rates among minorities at
a given level of effort/cost in community-based surveys.
Additionally, extending the number of telephone contact
attempts, sending out additional mailings, and extending
the data collection period have proven to be effective tech-
niques for overcoming low contact rates and increasing
recruitment of minorities for research, though at a higher
cost (18, 23).
To clarify the discrepancy between our findings and the
literature highlighting lower participation of African Amer-
icans in genetic studies, we examined the published partic-
ipation rates in the published genetic studies (11–17). Two
of these 7 studies were population-based, as ours was, and
the remaining 5 were other medical studies that requested
that the person participate in the genetic component. None
of these studies ascertained substance dependence or other
psychiatric illness. Although all published genetic studies
had significantly lower participation rates (P < 0.05) among
African Americans as compared with European Americans
(11–17), the magnitude of the difference between partic-
ipation rates was small relative to the sample size of the
individual studies (Table 3). Therefore, the hypothesis that
willingness to participate does not seem to be a barrier
in genetic studies is supported by previously published
A limitation of our study is that we did not know the
precise demographic characteristics of the unscreened sub-
jects. We reduced this limitation by comparing the zip codes
of the unscreened subjects and the reasons for lack of
screening with demographic data on subjects aged 25–44
years from US Census 2000. Although there was an associ-
ation between the proportion of people we failed to contact
and the proportion of African Americans in a zip code, this
association was highly confounded by poverty and other
socioeconomic variables. Therefore, we were unable to sep-
arate the contributions of ethnicity and poverty at the step
prior to contact. Interestingly, during community recruit-
ment for a study involving an invasive test, low-income
European Americans were found to be the most difficult
to contact (24). This suggests that poverty, rather than eth-
nicity, may be the dominant force behind the difficulty with
locating and contacting subjects.
Table 3. Participation Rates in Published Genetic Studies, by Ethnicity, 2000–2008
European AmericansAfrican Americans
Aagaard-Tillery, 2006 (11) Women enrolled in a study of
consented to unrestricted use
of maternal and fetal DNA
1,727 76 1,6827434
Espeland, 2006 (12)Volunteers for a study of
type 2 diabetes
2,70692 66682 67
Ford, 2006 (13) Colorectal cancer patients1,055 6323444
Green, 2006 (14)Participants in a multiethnic
study of atherosclerosis
McQuillan, 2006 (15) Participants in the National
Health and Nutrition
Examination Survey who
consented to ‘‘future genetic
2,878 901,026 8821
Mezuk, 2008 (16) Participants in the Baltimore,
Maryland, portion of the
Area Study who consented
to ‘‘future genetic research’’
662 83374 824
Williams, 2000 (17)Participants in the Family
Heart Study who consented
to ‘‘future DNA testing’’
1,875981,965 89 177
aAll participation rates in African Americans were significantly lower (P < 0.05) than participation rates in European Americans.
bThe additional number of African Americans who would be included in the study if the participation rate in African Americans were the same as
that in European Americans.
342 Hartz et al.
Am J Epidemiol. 2011;174(3):336–344
Subjects may have passively avoided participation in our
study by either refusing the telephone screening or declining
to answer the phone. Interestingly, avoiding contact was
inversely correlated with proportion of African Americans
in the zip code: The highest rates of both refusing the tele-
phone screening and not answering the phone were in the
zip codes with the lowest proportion of African Americans.
As we expand genetic databases to include more minority
populations, it is important to understand potential barriers
to minority recruitment. It is widely believed that minority
populations in the United States, particularly African Amer-
icans, have a distrust of genetic research that leads to lower
participation rates (7). In contrast, we found that eligible
African Americans participate in genetic studies as fre-
quently as European Americans. The major barrier to mi-
nority recruitment in our study was the fact that African
Americans were more difficult to locate in the community.
Notably, because of decreased access of African Americans
to health care in comparison with European Americans (25),
recruitment of African Americans at clinical centers is
likely to be less representative than community-based re-
cruitment. Although addressing feelings of distrust of med-
icaland genetic research inminoritiesmay remainimportant
generally, our study suggests that increasing the participa-
tion of African Americans in genetic databases may be
achieved by increasing efforts to locate and contact them.
Author affiliations: Department of Psychiatry, School of
Medicine, Washington University, St. Louis, Missouri (Sarah
M. Hartz, Laura J. Bierut); Behavioral Health and Criminal
Justice Research Division, Research Triangle Institute Inter-
national, Research Triangle Park, North Carolina (Eric O.
ington University, St. Louis, Missouri (Nancy L. Saccone);
Department of Psychiatry, Tobacco Use Research Center,
University of Minnesota, Minneapolis, Minnesota (Dorothy
Hatsukami); and Department of Epidemiology, College of
Human Medicine, Michigan State University, East Lansing,
Michigan (Naomi Breslau).
The authors represent investigators in the Collaborative
Study on the Genetics of Nicotine Dependence.
This work was supported by National Institutes of Health
grants P01 CA089392 from the National Cancer Institute,
U01 HG004422 from the National Human Genome Re-
search Institute, R01 DA019963 and K02 DA021237 from
the National Institute on Drug Abuse, and T32 MH014677
from the National Institute of Mental Health, and by Clin-
ical and Translational Science Award UL1RR024992.
The funding organizations had no role in the design and
conduct of the study; in the collection, analysis, and inter-
pretation of the data; or in the preparation, review, or ap-
proval of the manuscript.
Dr. Laura J. Bierut is listed as an inventor on US patent
20070258898(‘‘Markers of Addiction’’),coveringthe useof
certain single nucleotide polymorphisms in determining the
diagnosis, prognosis, and treatment of addiction. Dr. Nancy
L. Saccone is the spouse of Dr. Scott Saccone, who is also
listed as an inventor on the above patent. Dr. Bierut acted as
a consultant for Pfizer, Inc., in 2008.
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