About the Study

The Cameron County Hispanic Cohort (CCHC):

CCHC team

The CCHC is a cohort of Mexican Americans established in 2004 and currently numbering 4,584 individuals living on the Texas-Mexcio border (Figure1).22,25,37,38 The CCHC has been funded by the National Center for Minority Health Disparity (MD000170 P20, Dr. McCormick, PI; UL1 TR000371). Dr. Fisher-Hoch (contact PI of this proposal) along with Dr. McCormick has directed, developed, and expanded the cohort over 14 years. The provides a low income, homogenous ethnic population with high health risk which is largely missing from large national cohorts. The CCHC recruitment and examinations will be in the CTSA supported Clincal Research Unit which is located at Valley Baptist Medical Center Brownsville in donated space. Further recruitment at our other CRU's in Hidalgo and Laredo enlarges the sampling from of this cohort.

map3 Composition of the CCHC:

The CCHC (N=4,584) is recruited from randomly ascertained households, and is enriched for older participants. The mean age of the population at baseline is 47.8 years (median 46.9). At baseline, 62% of participants were over 40 years of age. Currently, 72% of participants are over 40 years of age, nearly half (52%) are over 50 years of age, and 98% identify themselves as Mexican American. To better understand the ethnic background of this population and the potential impact of ancestry genetics and culture, we assessed admixture using ancestry informative markers. The median proportion of European ancestry was 45.8% (coefficient of variation (CV) 32.5%), median African ancestry 11.0% (CV 59.5%), and median Amerindian ancestry 42.9% (CV 37.0%).

Population characteristics:

The majority of the cohort has been recruited in Brownsville which has a large population of Mexican Americans resident for several generations. It is an American city with a strong Mexican flavor and culture with strong family and community ties. Laredo has a similar population and is the oldest city on the south Texas border (established 1755, population 236,091, 95.6% Hispanic) also with a large long-time resident Mexican American population. Most of the Hispanics along the border are Mexican Americans, particularly in the poorer communities and many have relatives in large cities across Texas and the United States (U.S.), Hispanics are the most rapidly growing minority in the U.S. now accounting for ~58 million, and constituting 37.6% of the population of Texas most of whom (31.6%) are Mexican American.3 This ethnic group generally represents a difficult-to-reach, low-income population with high health risk which is mostly missing from large national cohorts.

 Composition of the CCHC

The CCHC is recruited from randomly ascertained households, and is enriched for older participants. The mean age of the population at baseline is 47.8 years (median 46.9). Currently, 72% of participants are over 40 years of age, nearly half (52%) are over 50 years of age, and 98% identify themselves as Mexican American. The median proportion of European ancestry is 45.8%, median African ancestry 11.0% (CV 59.5%), and median Amerindian ancestry 42.9% (CV 37.0%).

Sampling frame:

The CCHC is a true randomly-selected cohort. This relatively homogenous Mexican American sample is selected randomly by US Census Bureau tracts/blocks, stratified into socioeconomic strata (SES) quartiles, and not recruited through advertisement, as in most other cohorts. Recruitment is ongoing in households and occupied dwelling designated in randomization is visited up to 5 times. Poverty levels in the catchment area is over 30%, twice the national average (15.4%), making these districts among the very poorest in the country. Concentrating sampling in Brownsville and Laredo now give us a predominantly Mexican American cohort. We benefit from years of experience with this community, taking care to provide a safe environment for participants increasingly fearful of authority. Both recruitment and follow up present particular challenges in this population, which is among the poorest in the nation and often mobile. We have improved our follow up as we continue to build a respected identity in the community. 

Clinical Examination

Individuals from the households who agree to participate visit the Clinical Research Unit . We accommodate participants as much as possible, such as scheduling appointments for their convenience, e.g. Saturdays, and make home visits if requested. Once a participant arrives at the CRU, the protocols are explained in detail and an IRB approved individual written informed consent is obtained from each participant to participate in the examination and to allow the measurements, collection of data and bispecimens outlined below. The informed consent form specifically includes consent to access electronic medical records (EMR), consent for use of archived materials for new studies including genetics, and permission to be contacted for new studies and for follow up studies. All results are returned to participants with explanation, and recommendations for follow up are given if needed with advice to either visit their physician if they have one, or one of the local Federally Qualified Clinics (FQC). Participants may opt out of any part of the study at any time as they wish.

Robust methodology has been in place since 2004 that extensively phenotypes individuals using consistent, comprehensive protocols and procedures. Validated questionnaires are administered by staff in English or Spanish. These cover sociodemographics, medical and medication histories, behavioral/environmental, family medical histories, diet and physical activity, and alcohol and smoking behaviors. A mental health examination to assess anxiety, depression, and cognitive function is routinely administered using the validated instruments including the Center for Epidemiological Studies: Depression Scale and Zung’s Self-Rating Anxiety Scale (see CCHC website for further details). Complete medical histories are taken, and family histories include records of  sociodemographics, medical and family histories, diet, physical activity, smoking and alcohol use, and performing clinical examinations. We measure participants’ weight with their shoes removed using a portable electronic scale and record the weight to the nearest 0.2 kg. Height is measured to the nearest 0.2 cm with a stadiometer. Body mass index (BMI) is calculated and waist circumference (visceral adiposity) is determined at the level of the umbilicus to the nearest 0.2 cm, with participants in a standing position and breathing normally. We measure blood pressure according to the protocol described in the National High Blood Pressure Education Program(National Heart, 2003) and obtain an electrocardiogram (EKG). Participants are asked to fast for 10 hours prior to blood collection, and we reschedule any participants who have not fasted. We obtain routine clinical hematology (white blood cell count, differential, hematocrit, hemoglobin)  and chemistries (lipid profile, metabolic profile, urinalysis, liver function tests) and glycated hemoglobin, C-reactive protein, and urinalysis  are performed in our local Clinical Reference Laboratory (CRL) and the remainder of the specimens archived at optimal -80oC We perform in house insulin assays and Luminex adipocytokine panels.. In addition, Since 2012 we have sequentially added imaging modalities to all visits; specifically, ultrasound measures of carotid intimal thickness (cIMT), flow mediated dilatation (FMD), echocardiograms, and a range of measures of peripheral artery disease (PAD), using Doppler based techniques, and more recently retinal exam with optical coherence tomography with angiography, eye pressure, and a stool sample is collected for microbiome studies. We measure liver stiffness using the FibroScan VCTE-CAP technology. These new measures represent ancillary study content that builds upon the CCHC infrastructure.

The major areas of research revolve around obesity, diabetes, and their effect on heart disease, liver disease, infectious diseases and mental health. In addition, the CRU and CCHC serve as a means to evaluate the behavioral and biological effects of population based and clinical interventions. Several publications using data from this important minority, health disparity cohort are published and many more are in progress of Medicine in Houston. We are currently performing 5, 10 and 25-year follow-up visits to track our participants and their health. We obtain death certificates from the Center for Disease Control.

Specimen Archive

A separate freezer room with restricted access contains 15 ultra-low freezers for with a large archive of  specimens, liquid nitrogen, freeze dry equipment, general storage, and space for equipment used occasionally, and is supported by a backup generator (5-day capacity) for possible power failures (e.g., hurricanes). Specimens are frozen at minus 80oC at the collection sites, then transferred on frozen ice packs to the archive. This now includes longitudinal plasma, serum, DNA and peripheral blood RNA.  Stored specimens have been assayed for quality control showing high quality. Samples are managed and tracked using Pro® (Brooks Automation, Inc., Chelmsford, MA, USA).

Description of Research Questions that have been investigated in the CCHC and major findings:

In the context of the national epidemics of increasing obesity in adults (national prevalence 39.8%, 2015 data), Hispanics context of the national epidemics of increasing obesity in adults (national prevalence 39.8%, 2015 data), Hispanics have the highest prevalence (47.0%).41 Similarly the national prevalence of diabetes is 9.4%, but among Hispanics it is 12.1%, rising to 13.8% in Mexican Americans.42 We therefore first sought to establish the prevalence of obesity and diabetes in the CCHC population. Table 4 shows rates of diabetes and obesity considerably higher than those reported nationally. The CCHC represents a population with many chronic conditions that go undiagnosed.22,25 Findings in the CCHC are generalizable to the Mexican American population, and novel since this is an understudied minority.. For example, we have shown that the Framingham risk score used for predicting cardiovascular events is inaccurate in Mexican Americans.18-21 Another study showed that a high proportion of participants (77.8%) were found to be metabolically unhealthy. In addition to studies looking at cardiovascular risk factors, the CCHC data shows that the prevalence of liver disease, including cirrhosis and hepatocellular carcinoma, is much higher than the national rates. Furthermore, we have shown that hepatocellular carcinoma is the third most common cancer in men and seventh in women.46 We performed elastography to determine levels of hepatic fibrosis in CCHC participants and find that 15% had evidence of significant fibrosis, mostly presumed due to non-alcoholic liver disease. Given the general poor health of this community, the CCHC should allow for clear definition of some of the key biologic aspects of the nature and even veracity of the Hispanic Paradox observation. The availability of this population-based sample with extensive measures of cardiometabolic and cardiovascular disease, coupled with lifestyle and demographic data (such as place of birth and length of time in the US), provides a unique opportunity to examine the distribution of sub-clinical disease in the CCHC and the predictors of cardiovascular outcomes.

Community Outreach Projects

The BRC community outreach programs focus on health problems and solutions specific to the border area. Special areas of interest include intervention research with adults and children to prevent and control obesity and diabetes. Students in Brownsville have a great opportunity to gain invaluable experience in international health with numerous bi-national programs with Mexican organizations and studies in adjacent areas of Mexico.

Tu Salud Si Cuenta

The Your Health Matters!  Curricula are designed to provide scientifically accurate information to community health workers and people outside of the health profession about healthy food choices and physical activity in a manner that promotes individual behavior change and/or policy, environmental and system changes.  For more information, go to Your Health Matters Curricula and become educated on the Fitness For Life, Nutritious Eating, Growing Active Communities, Growing Active Healthy Communities and Tu Salud Si Cuenta. 

Outreach Media

Belinda Reininger: Designs and examines the effectiveness of interventions based on behavioral theory and the Ecological Model to improve health outcomes associated with obesity and related chronic diseases among Mexican Americans.

Brownsville Farmers’ Market

To fight an epidemic of obesity and its life-threatening complications in the Brownsville area, faculty and students at the BRC developed a strong weapon: a farmers’ market loaded with fresh fruits and vegetables. The Brownsville Farmers’ Market is a collaborative effort to provide locally grown produce and increase the awareness of chronic diseases associated with obesity. The market provides affordable fresh produce to the community, and it provides local farmers an outlet to sell their produce. It also gives health care experts the opportunity to educate shoppers on nutrition, obesity and diabetes.

Promotora Outreach

Community Health Workers (CHWs) or “Promotores” are the foundation of our work in the community, and lead our chronic disease management and prevention efforts. They are from the community, and understand the culture, language and needs of the participants we serve. The Brownsville Regional Campus employs over 20 CHWs, certified through a 160 hour course provided by the Texas Department of State Health Services (DSHS). They receive ongoing continuing education and training and are involved in research and service delivery. Our campus also has 6 DSHS certified CHW Instructors and has developed multiple training of trainers curriculum for continuing education delivered across the state.

CHW’s are trained in Motivational Interviewing, phlebotomy, case management, Diabetes education and teach exercise, nutrition and healthy cooking classes throughout the community. They also provide follow-up home visits to participants with high blood pressure, high BMI and/uncontrolled diabetes and work with community partners including clinics, mental health authority, community non-profits, schools and churches to address barriers to healthcare access, healthy lifestyle choices and disease management.

Obesity and Body Image among Mexican-Americans

The research is funded through Salud America!, a subdivision of the Robert Wood Johnson Foundation, whose aim is to reduce and prevent obesity among Latino youth.