Association of African genetic admixture with resting metabolic rate and obesity among women

OBJECTIVE: To investigate the role of genetic admixture in explaining phenotypic variation in obesity-related traits in a sample of African-American women (n = 145) and to determine significant associations between obesity traits and admixture genetic markers. RESEARCH METHODS AND PROCEDURES: Associations between genetic admixture and BMI, resting metabolic rate, fat mass, fat-free mass, and bone mineral density were tested using linear regression considering the estimation of admixture by 1) a maximum-likelihood approach (MLA) and 2) a Bayesian analysis. RESULTS: Both the conservative MLA and the Bayesian approach support an association between African genetic admixture and BMI. Evidence for the associations of African genetic admixture with fat mass and fat-free mass was supported by the Bayesian analysis; the MLA supported an association with bone mineral density. When the individual ancestry informative markers that were used to estimate admixture were tested for associations with BMI, significant associations were identified in chromosomes 1, 11, and 12. DISCUSSION: These results provide evidence supporting the application of admixture mapping methods to the identification of genes that result in higher levels of obesity among African-American women. Further research is needed to replicate and further explore these findings.     

Socioeconomic Status and Lung Cancer: Unraveling the Contribution of Genetic Admixture

Objectives. We examined the relationship between genetic ancestry, socioeconomic status (SES), and lung cancer among African Americans and Latinos.Methods. We evaluated SES and genetic ancestry in a Northern California lung cancer case–control study (1998–2003) of African Americans and Latinos. Lung cancer case and control participants were frequency matched on age, gender, and race/ethnicity. We assessed case–control differences in individual admixture proportions using the 2-sample t test and analysis of covariance. Logistic regression models examined associations among genetic ancestry, socioeconomic characteristics, and lung cancer.Results. Decreased Amerindian ancestry was associated with higher education among Latino control participants and greater African ancestry was associated with decreased education among African lung cancer case participants. Education was associated with lung cancer among both Latinos and African Americans, independent of smoking, ancestry, age, and gender. Genetic ancestry was not associated with lung cancer among African Americans.Conclusions. Findings suggest that socioeconomic factors may have a greater impact than genetic ancestry on lung cancer among African Americans. The genetic heterogeneity and recent dynamic migration and acculturation of Latinos complicate recruitment; thus, epidemiological analyses and findings should be interpreted cautiously.Associations between socioeconomic status (SES) and cancer incidence or mortality and accompanying racial/ethnic differences are common findings across cancers and populations.1–9 An inverse association between socioeconomic measures and lung cancer incidence and mortality is a consistent observation among populations,7,10–18 especially among men, although for lung cancer mortality in the United States, this pattern is a reversal of that of earlier decades.19 Socioeconomic measurements are also known to vary across diverse populations.20 In the United States, African Americans and Latinos have, on average, lower education, larger household sizes, and lower income and are frequently unmarried compared with Whites.21–24 Smoking is more prevalent among people characterized by low socioeconomic factors such as low education, low income, and working-class occupations.20,25–27 Studies examining the relationship between SES and lung cancer, or cancer in general, have used surveys and registries with large sample sizes, thereby increasing the precision of effect estimates.7,11,12 However, these studies have been constrained by the lack of data on important risk factors for lung cancer11 or have linked aggregate socioeconomic exposure data to individual-level disease status.6,7,11 Ascribing attributes of a group to an individual may not be appropriate and can result in inaccurate inferences, especially if the exposure, SES, is misclassified.28,29Despite known disparities in lung cancer incidence30 and consistently observed associations between SES and both lung cancer and race/ethnicity, few studies have examined this interrelationship, which is thought to result from a complex interplay of environmental, social, economic, and genetic factors. Using incident cancer registry data, Krieger et al.31 observed an inverse relationship between lung cancer incidence and socioeconomic deprivation among African Americans but an increase in incidence with economic prosperity among Latinos. A study examining lung cancer among Latinos found that incidence increased as income increased and the percentage of Latinos residing in the census tract decreased.32 Many studies examining socioeconomic differences in lung cancer risk have suggested the increased risk cannot be fully explained by smoking, occupational, or dietary exposures,13,15,16,33,34 whereas others have found that controlling for several measures such as smoking,35 dietary fat, and perceived health removed associations with SES.17 Some studies examining racial/ethnic differences in lung cancer found ethnic differences disappeared after adjusting for SES.6,7,11 Together, these findings highlight the complexities of understanding the relationship among SES, lung cancer, and race/ethnicity.Self-reported race/ethnicity represents a combination of several factors—genetic, social, economic, and environmental.36 Moreover, because of the ancestral heterogeneity of Latinos and African Americans, self-reported race/ethnicity does not provide precise genetic information. Recent advances in statistical tools and identification of genetic markers informative for ancestry have enabled the genetic heterogeneity of populations to be described and applied to epidemiological studies. Genetic ancestry associations are a useful tool to suggest that a genetic component contributes to disease disparities and admixture mapping is implemented to identify genetic factors contributing to disease.37,38 Of importance is that genetic ancestry may be associated with socioeconomic factors.39–43 For example, Sánchez et al.42 revealed Amerindian ancestry was greater in individuals with fewer years of education. Complex associations among SES, ancestry, and lung cancer require examination to disentangle their contributions to lung cancer. We examined the relationship among SES, genetic ancestry, and lung cancer in a case–control study conducted with African Americans and Latinos.     

Heterogeneity in management of diabetes mellitus among Latino ethnic subgroups in the United States.

BACKGROUND: Recent debate suggests that general racial/ethnic categories may obscure potentially important subgroup differences within minority groups. The purpose of this study was to examine the quality of diabetes care among ethnic subgroups of the Latino population in the United States while accounting for aspects of acculturation and access to care. METHODS: We evaluated adults (> or =18 years old) with previously diagnosed diabetes in the 2003 National Health Interview Survey (n = 2136; United States population estimate = 13,471,587). The Latino subgroups (n = 373; United States population estimate = 1,556,259) were Mexicans, Puerto Ricans, and Other Latinos. Through a series of logistic regressions we examined ethnic group and quality of care for diabetes while controlling for demographics, access to care, and acculturation. RESULTS: Among Latinos, 43% conducted their interview in Spanish and 59% were immigrants to the United States. Ethnic group differences were apparent in the analyses. In a logistic regression analysis including all Latinos, with Puerto Ricans as the reference group, Mexicans (odds ratio, 0.24; 95% CI, 0.07-0.85) and Other Latinos (odds ratio, 0.15; 95% CI, 0.04-0.58) were significantly less likely to have only one doctor for their diabetes care. Mexicans were less likely than Puerto Ricans (odds ratio 0.39; 95% CI, 0.18- 0.84) to know about glycosylated hemoglobin. Similarly, among Latino immigrants, Mexicans (odds ratio, 0.13; 95% CI, 0.02-0.81) and Other Latinos (odds ratio, 0.09; 95% CI, 0.01-0.63) were significantly less likely than Puerto Ricans to have only one doctor for their diabetes care and management. Measures of acculturation and immigration were not independent predictors of diabetes quality of care. CONCLUSIONS: Differences in diabetes management exist between Latino ethnic subgroups; treating Latinos in the United States as one homogenous category may be a barrier to the appropriate provision of care.     

Relationship of prevalence of non-insulin-dependent diabetes mellitus to Amerindian admixture in the Mexican Americans of San Antonio, Texas

A genetic and epidemiological survey of non-insulin-dependent diabetes mellitus (NIDDM) was conducted among the Mexican Americans residing in three socioeconomically distinct areas of San Antonio, Texas: a low socioeconomic (SES) traditional area (barrio), a middle SES, ethnically balanced area (transitional), and a high SES, predominantly Anglo area (suburb). Seventeen polymorphic markers were used to relate the prevalences of NIDDM with the extent of Amerindian ancestry of 1,237 Mexican Americans of these three residential areas. While only the RH and haptoglobin loci showed evidence of association with NIDDM, an admixture analysis of the combined allele frequency data revealed a pattern of decreasing NIDDM prevalence with increasing socioeconomic status (as approximated by neighborhood of residence) and a parallel decrease in Amerindian ancestry. The rank-order correlation between NIDDM prevalence and Amerindian admixture is 0.943 (P less than .001) for the crude prevalence rate and 0.829 (P less than .02) for the age-adjusted rate. Nested gene diversity analysis revealed that the heterogeneity of allele frequencies is more pronounced when individuals were classified by their NIDDM disease status as compared to the classification by neighborhood. Estimation of Amerindian ancestry of each individual did not reveal any significant change in the shape of the distributions of individual admixture proportions in diabetics as compared to the controls. Nevertheless, the results suggest that genetic factors partially explain the differences in NIDDM prevalence observed between the Mexican American and Anglo populations in the southwestern United States.     

Information on ancestry from genetic markers

It is possible to estimate the proportionate contributions of ancestral populations to admixed individuals or populations using genetic markers, but different loci and alleles vary considerably in the amount of information that they provide. Conventionally, the allele frequency difference between parental populations (delta) has been used as the criterion to select informative markers. However, it is unclear how to use delta for multiallelic loci, or populations formed by the mixture of more than two groups. Moreover, several other factors, including the actual ancestral proportions and the relative genetic diversities of the parental populations, affect the information provided by genetic markers. We demonstrate here that using delta as the sole criterion for marker selection is inadequate, and we propose, instead, to use Fisher's information, which is the inverse of the variance of the estimated ancestral contributions. This measure is superior because it is directly related to the precision of ancestry estimates. Although delta is related to Fisher's information, the relationship is neither linear nor simple, and the information can vary widely for markers with identical deltas. Fortunately, Fisher's information is easily computed and formally extends to the situation of multiple alleles and/or parental populations. We examined the distribution of information for SNP and microsatellite loci available in the public domain for a variety of model admixed populations. The information, on average, is higher for microsatellite loci, but exceptional SNPs exceed the best microsatellites. Despite the large number of genetic markers that have been identified for admixture analysis, it appears that information for estimating admixture proportions is limited, and estimates will typically have wide confidence intervals.     

Developing a family-based diabetes program for Latino immigrants: do men and women face the same barriers?

This study examined barriers and facilitators to diabetes self-management among Latino immigrants with diabetes and whether similarities and differences were observed by gender. Eight focus groups were conducted with 24 women and 21 men Latinos; four focus groups involved women only and four involved men only. Themes were identified using a combined deductive/inductive approach and an iterative process of consensus coding. Gender similarities and differences emerged. Barriers to self-management were primarily social for the women, whereas for men, structural aspects related to work were prominent. Interventions aimed at improving diabetes self-management among US Latino immigrants should consider tailored approaches to help men and women overcome distinct barriers.     

Alcohol Use Among Latinos: A Comparison of Pre-Immigration,Post-Immigration,and US Born Latinos

US born Latinos have higher rates of alcohol use than Latino immigrants. Yet, little is known about drinking patterns of Latinos before their immigration to the US This exploratory study compares the past month regular, binge, and heavy alcohol use patterns of Latino immigrants prior to immigration with that of post-immigration and US born Latinos. Data on past month alcohol use prior to immigration was collected from 516 recent adult Latino immigrants. Results were compared with US born and post-immigration Latinos using national aggregate data. Alcohol use patterns among Latino immigrants prior to immigration were similar to that of US born Latinos. Alcohol use patterns were lower among Latinos after immigration when compared to pre-immigration and US born Latinos. This study provides a foundation for further exploration of the drinking patterns of Latinos in the US before they immigrated to this country. Findings suggest more research is needed to uncover the underlying factors associated with the higher rates of alcohol use among Latinos prior to their immigration when compared to alcohol use patterns of post-immigration Latinos.     

Analysis of pedigree data in populations with multiple ancestries: Strategies for dealing with admixture in Caribbean Hispanic families from the ADSP

Multipoint linkage analysis is an important approach for localizing disease‐associated loci in pedigrees. Linkage analysis, however, is sensitive to misspecification of marker allele frequencies. Pedigrees from recently admixed populations are particularly susceptible to this problem because of the challenge of accurately accounting for population structure. Therefore, increasing emphasis on use of multiethnic samples in genetic studies requires reevaluation of best practices, given data currently available. Typical strategies have been to compute allele frequencies from the sample, or to use marker allele frequencies determined by admixture proportions averaged over the entire sample. However, admixture proportions vary among pedigrees and throughout the genome in a family‐specific manner. Here, we evaluate several approaches to model admixture in linkage analysis, providing different levels of detail about ancestral origin. To perform our evaluations, for specification of marker allele frequencies, we used data on 67 Caribbean Hispanic admixed families from the Alzheimer's Disease Sequencing Project. Our results show that choice of admixture model has an effect on the linkage analysis results. Variant‐specific admixture proportions, computed for individual families, provide the most detailed regional admixture estimates, and, as such, are the most appropriate allele frequencies for linkage analysis. This likely decreases the number of false‐positive results, and is straightforward to implement.     

Acculturation and Cardiovascular Behaviors Among Latinos in California by Country/Region of Origin

Despite generally lower socioeconomic status and worse access to healthcare, Latinos have better overall health outcomes and longer life expectancy than non-Latino Whites. This "Latino Health Paradox" has been partially attributed to healthier cardiovascular (CV) behaviors among Latinos. However, as Latinos become more acculturated, differences in some CV behaviors disappear. This study aimed to explore how associations between acculturation and CV behaviors among Latinos vary by country of origin. Combined weighted data from the 2005 and 2007 California Health Interview Survey (CHIS) were used to investigate associations between acculturation level and CV behaviors among Latinos by country of origin. Among all Latinos, increased acculturation was associated with more smoking, increased leisure-time physical activity, and greater consumption of fast foods, but no change in fruit/vegetable and less soda intake. These trends varied, however, by Latino sub-groups from different countries of origin. Country of origin appears to impact associations between acculturation and CV behaviors among Latinos in complex ways.     

Availability of Commonly Consumed and Culturally Specific Fruits and Vegetables in African-American and Latino Neighborhoods

Although the importance of culture in shaping individual dietary behaviors is well-documented, cultural food preferences have received limited attention in research on the neighborhood food environment. The purpose of this study was to assess the availability of commonly consumed and culturally specific fruits and vegetables in retail food stores located in majority African-American and Latino neighborhoods in southwest Chicago, IL. A cross-sectional survey of 115 stores (15% grocery stores, 85% convenience/corner stores) in African-American neighborhoods and 110 stores (45% grocery stores, 55% convenience/corner stores) in Latino neighborhoods was conducted between May and August of 2006. χ² tests were used to assess differences in the availability (presence/absence) of commonly consumed (n=25) and culturally specific fruits and vegetables for African Americans (n=16 varieties) and Latinos (n=18 varieties). Stores located in neighborhoods in which the majority of residents were African American or Latino were more likely to carry fresh fruits and vegetables that were culturally relevant to the dominant group. For example, grocery stores located in Latino neighborhoods were more likely to carry chayote (82.0% vs 17.6%, P<0.05), whereas grocery stores located in African-American neighborhoods were more likely to carry black-eyed peas (52.9% vs 20%, P<0.05). Most stores, however, carried fewer than 50% of commonly consumed or culturally specific fruits and vegetables. Findings from this study highlight that limited availability of culturally specific as well as commonly consumed fruits and vegetables in the neighborhood may be a barrier to fruit and vegetable consumption among African Americans and Latinos.     

The Theory of Planned Behavior as a Model of Intentions for Fighting Among African American and Latino Adolescents

OBJECTIVES: To test the theory of planned behavior as a model for predicting and understanding behavioral intentions for fighting among inner-city adolescents and to determine whether its predictive power differs as a function of ethnicity (African American versus Latino). METHODS: Participants were 956 (511 females, 445 males) African American (n = 702) and Latino (n = 254) adolescents (mean age = 12.72 years; SD = 1.12) recruited from sixth, seventh, and eighth grade classes in public middle schools serving two inner-city communities in New Jersey who completed self-administered, confidential questionnaires. RESULTS: Consistent with the theory of planned behavior, hierarchical multiple regression analyses revealed that attitudes, subjective norms, and perceived behavioral control predicted intentions for fighting. Although the theory of planned behavior accounted for substantial variance in intentions to fight in both ethnic groups, it accounted for greater variance among Latinos than among African Americans. The strength of the relations of subjective norms and perceived behavioral control to intentions was similar in the two groups. but the relation of attitudes to intentions to fight was significantly stronger among Latinos. CONCLUSIONS: The findings strongly suggest that the theory of planned behavior provides a potentially useful conceptual framework for guiding the creation of interventions for African American and Latino adolescents that are designed to reduce violent behavior and the tragedies that such behavior leaves in its wake.     

Neighborhood contributions to psychological distress among Latino New York City adults

Objective: Neighborhood-level factors such as ethnic densities and social cohesion have been negatively associated with psychological distress among Latino Americans. Yet, existing evidence is based on either specific neighborhood factors or particular Latino subgroups. The objective of the study was to assess difference in psychological distress between each of four Latino subgroups (Puerto Ricans, Dominicans, Mexicans, other Latinos) and non-Latino white adults in New York City, and quantify total neighborhood-level influence on these differences.

Design: We used the combined Community Health Survey data from 2009, 2010, and 2012 surveys. We estimated the odds ratios (ORs) for self-reported non-specific psychological distress (Kessler-6 questions scale ≥ 13) by race/ethnicity using logistic regression models. We further adjusted these estimates for both observed and unobserved neighborhood-level confounding using the conditional pseudolikelihood method for complex survey data.

Results: Puerto Ricans were more likely to be psychologically distressed (OR?=?1.58, 95% CI?=?1.18, 2.12) compared with non-Latino whites, whereas the opposite was seen in other Latino subgroups. Accounting for full neighborhood-level confounding increased the disparity for Puerto Ricans (OR?=?1.79, 95% CI?=?1.26–2.54). For the other subgroups, lower odds of psychological distress were no longer observed or attenuated after accounting for neighborhood-level confounding. Overall neighborhood-level factors were associated with lower psychological distress at greater extent among all Latinos subgroups versus non-Latino whites in New York City.

Conclusion: Despite substantial variations of psychological distress across Latino subgroups, the study shows evidence that neighborhood-level factors might play a protective role in all Latino subgroups.     

Neighborhood Context and Hypertension Outcomes Among Latinos in Chicago

Although a health advantage in hypertension has been documented among Latinos, this advantage appears to be eroding. Of particular concern is the observation that Latinos are less likely to be screened and treated for hypertension and to having it controlled. Scholars have suggested that, above and beyond individual-level factors, neighborhood characteristics may be important predictors of health and health care. We analyzed 2001–2003 data from the Chicago Community Adult Health Study to examine (a) the relationship between the Latino and immigrant composition of neighborhoods in Chicago and several outcomes among Latinos: having hypertension, utilizing hypertension-related health care, and being treated for hypertension; and (b) whether there was a differential effect of neighborhood Latino/immigrant concentration by language of interview and nativity status. We controlled for additional neighborhood characteristics relevant to hypertension and to the availability and accessibility of health care resources. Neighborhoods with higher concentrations of immigrants and Latinos were associated with Latinos having lower odds of hypertension (OR?=?0.60, p?=?0.03). However, among those with hypertension, our results point to deleterious effects on hypertension care (OR?=?0.55, p?=?0.06) and treatment (OR?=?0.54, p?=?0.04) associated with living in neighborhoods with higher concentrations of immigrants and Latinos. We detected no significant interaction effects between immigrant/Latino neighborhood composition and language of interview or being an immigrant in this sample. These results suggest that improving access to care for Latinos with hypertension requires enhanced placement of community clinics and other safety-net health centers in neighborhoods with higher proportions of immigrants and Latinos.     

A multiethnic cohort in Hawaii and Los Angeles: baseline characteristics

The authors describe the design and implementation of a large multiethnic cohort established to study diet and cancer in the United States. They detail the source of the subjects, sample size, questionnaire development, pilot work, and approaches to future analyses. The cohort consists of 215,251 adult men and women (age 45-75 years at baseline) living in Hawaii and in California (primarily Los Angeles County) with the following ethnic distribution: African-American (16.3%), Latino (22.0%), Japanese-American (26.4%), Native Hawaiian (6.5%), White (22.9%), and other ancestry (5.8%). From 1993 to 1996, participants entered the cohort by completing a 26-page, self-administered mail questionnaire that elicited a quantitative food frequency history, along with demographic and other information. Response rates ranged from 20% in Latinos to 49% in Japanese-Americans. As expected, both within and among ethnic groups, the questionnaire data show substantial variations in dietary intakes (nutrients as well as foods) and in the distributions of non-dietary risk factors (including smoking, alcohol consumption, obesity, and physical activity). When compared with corresponding ethnic-specific cancer incidence rates, the findings provide tentative support for several current dietary hypotheses. As sufficient numbers of cancer cases are identified through surveillance of the cohort, dietary and other hypotheses will be tested in prospective analyses.     

Screening Latino adolescents for latent tuberculosis infection (LTBI)

OBJECTIVES: To investigate the rates of latent TB infection (LTBI) in a sample of young people in San Diego County and examine potential predictors of a positive tuberculin skin test (TST). METHODS: Latino and foreign-born students from ten public middle and high schools were invited to screenings along with a random 10% sample of all other students. After obtaining parental consent, Mantoux tests were placed (N=2,698) and read (n=2,667 [98.9%]) in 48-72 hours. A positive TST was defined as > or =10 mm induration. The mean age of the sample was 14.34 years (SD=1.81); 50.1% were female (n=1,353); 78.5% were Latino (n=2,108); 35.7% were foreign-born (n=939); and 44.3% were uninsured (n=930). RESULTS: The positive TST rate for Latinos was 21.8% vs. 5.6% for non-Latinos, p<0.001. Foreign-born Latinos had the highest infection rate (31.3%), followed by foreign-born non-Latinos (20.4%), U.S.-born Latinos (15.4%), and U.S.-born non-Latinos (1.0%), p<0.001. Logistic regression was conducted to determine predictors of TST positivity. Being Latino (odds ratio [OR]=3.27), uninsured (OR=1.60), foreign-born (OR=3.90), and living in the south county region closest to the U.S./Mexico border (OR=2.72) were significant predictors. CONCLUSIONS: Results suggest that Latino youth near the California/Mexico border are at high risk for infection, for remaining undiagnosed, and for being under-treated for LTBI.     

The Relationship Between Ethnicity and Fatigue in a Community-Based Sample

Estimates of fatigue severity vary according to whether participants are recruited from hospital-based tertiary care clinics, primary medical care, or community-based samples. Sampling methodology is a central issue in epidemiological research because differences in utilization and differential access to health care among participants of varying sociodemographic backgrounds have biased earlier prevalence and severity estimates of fatigue. Most existing studies do not employ randomly selected representative samples and do not examine ethnic and other sociodemographic differences. Findings presented herein derive from a community-based study of fatigue severity and prevalence in an ethnically and socioeconomically diverse sample of 28,673 households in Chicago. The study examined sociodemographic differences in fatigue across African American, White, Latino, and Asian American samples according to age, gender, socioeconomic status, marital status, and parental status. Latinos who were female, Latinos who were older, and Latinos of higher socioeconomic status reported the highest relative severity of fatigue. The implications of these findings are discussed.     

Latino parents' perceptions of their ability to prevent obesity in their children

The obesity epidemic in Latino children has reached staggering proportions. This study explored Latino parents' perceptions of their ability to prevent obesity in children. Three focus groups were conducted with 26 Latino parents of preschoolers at a New York City Head Start program. Parents perceived high levels of ability to prevent obesity primarily via dietary influence. Four factors negatively impacted parents' ability: family history, intergenerational and interparental issues, adolescence, and societal pressures. Culturally effective, family-based obesity interventions among Latinos should build upon parental perceptions of ability to prevent obesity, while simultaneously helping parents address the factors they perceive challenge this ability.     

The Association between Multiple Domains of Discrimination and Self-assessed Health: A Multilevel Analysis of Latinos and Blacks in Four Low-Income New York City Neighborhoods

Objective. This study examines the association between discrimination due to race and other attributes (e.g., sex, age) and self-assessed mental and physical health among Latinos and blacks.
Data Source. Latino and black adult participants ( n =873) identified by random digit dialing were interviewed by telephone in four low-income neighborhoods in New York City: the South Bronx, East Harlem, Central Harlem, and Bedford-Stuyvesant.
Study Design. In this cross-sectional study, generalized estimating equations were used to fit multilevel multivariable models to test the association between discrimination and poor mental and physical health while controlling for socioeconomic status, access to health care, social support, smoking, and the racial and ethnic composition of each neighborhood.
Principal Findings. Discrimination due to race and discrimination due to other attributes were associated with poor self-assessed mental but not physical health in separate multivariable models. Persons who experienced multiple domains of discrimination had a greater probability of reporting poor mental health than persons who experienced no discrimination.
Conclusions. Discrimination due to race and other attributes was a significant correlate of mental health among Latinos and blacks independent of other accepted determinants of health.     

Using Genetic Admixture to Study the Biology of Obesity Traits and to Map Genes in Admixed Populations

Differences among ethnic and racial groups in obesity-related traits have been clearly established in the scientific literature. To explore the genetic component underlying these differences, the genetic admixture approach has been used. In this approach, ancestry informative genetic markers are used to estimate a quantitative value representing the degree of ancestral background in individuals of admixed genetic background. Genetic admixture has been successfully used to explain racial and ethnic variation in obesity related traits; however, the understanding and measure of cultural and environmental components that also influence these phenotypes still requires further exploration     

PAMAM: Power analysis in multiancestry admixture mapping

Admixed populations arise when two or more previously isolated populations interbreed. Admixture mapping (AM) methods are used for tracing the ancestral origin of disease-susceptibility genetic loci in the admixed population such as African American and Latinos. AM is different from genome-wide association studies in that ancestry rather than genotypes are tracked in the association process. The power and sample size of AM primarily depend on proportion of admixture and differences in the risk allele frequencies among the ancestral populations. Ensuring sufficient power to detect the effect of ancestry on disease susceptibility is critical for interpretability and reliability of studies using AM approach. However, there is no power and sample size analysis tool existing for AM studies in admixed population. In this study, we developed power analysis of multiancestry AM (PAMAM) to estimate power and sample size for two-way and three-way population admixtures. PAMAM is the first web-based bioinformatics tool developed to calculate power and sample size in admixed population under a variety of genetic and disease phenotype models. It is a valuable resource for investigators to design a cost-efficient study and develop grant application to pursue AM studies. PAMAM is built on JavaScript back-end with HTML front-end. It is accessible through any modern web browser such as Firefox, Internet Explorer, and Google Chrome regardless of operating system. It is a user-friendly tool containing links for support information including user manual and examples, and freely available at https://research.cchmc.org/mershalab/PAMAM/login.html .