The MESA is a large, population based, multi-center cohort study designed to describe risk factors related to the development and progression of subclinical coronary atherosclerotic heart disease. The cohort is comprised of 6814 Caucasian, African-American, Hispanic, and Asian men and women aged 45-84 who were clinically free from cardiovascular disease at baseline and followed for a period of eight years. Study participants were recruited from six communities (Los Angeles County, CA; Manhattan, New York, NY; Baltimore, MD; Chicago, IL; St. Paul, MN and Forsyth County, NC) in the United States. Internal Review Boards at each participating centers approved the studies and each participants gave written informed consent. Participants with active cancer, cognitive impairment, or weight greater than 300 pounds (136 kg) and pregnant individuals were excluded. This study has been described in detail elsewhere[26].

In addition to the MESA exclusion criteria, we additionally excluded for the following: significant alcohol consumption (defined as > 14 drinks on average per week in men and > 7 drinks on average per week in women), a history of Hepatitis C and the absence of a visible liver and/or spleen on cardiac CT (Figure 1). This study focused on comparing Hispanics of Mexican and Caribbean Origin (Dominican and Puerto Rican). Hispanics of Cuban Origin were excluded due to the small number of individuals with NAFLD; n = 2 out of total n = 41 total participants. Hispanics that were described as of Central American origin (n = 46), South American origin (n = 66) and “other” were excluded (n = 12) in an effort to maintain homogeneity.

Open in New Tab   Full Size Figure   Download Figure

Figure 1 Multi-ethnic study of atherosclerosis participants: Exclusion criteria. Study exclusion criteria. Participants without adequate imaging for liver:spleen ratio calculations were excluded as were individuals with self-reported history of hepatitis C and significant alcohol consumption (> 14 drinks per week in men, > 7 drinks a week in women); Non-Hispanic and Hispanics not of Caribbean origin were excluded; Cubans, due to small number with non-alcoholic fatty liver disease (n = 2) were also excluded. MESA: Multi-ethnic study of atherosclerosis.

We utilized the baseline serum, anthropometric and radiographic measurements obtained between 2000 and 2002 of the MESA study. Information on sociodemographic factors (age, sex, and education), lifestyle factors (alcohol consumption and smoking status) and self-reported medical history (hypertension, diabetes, liver disease and cirrhosis) were collected at the baseline examination using standardized questionnaires. A central laboratory (University of Vermont, Burlington) measured levels of total and HDL cholesterol, triglycerides, plasma glucose, and high-sensitivity C-reactive protein in blood samples obtained after a 12 h fast. Waist circumference was measured horizontally at the level of the umbilicus. Hip girth was measured at the maximum circumference of the buttocks. Body mass index was calculated as weight in kilograms divided by height in meters squared. Homeostatic model assessment was used to measure insulin resistance (HOMA-IR) calculated as fasting glucose (mg/dL) × fasting insulin (μU/mL) /405[27].

All participants in the MESA study obtained non-contrast cardiac computed tomography (CT) scans at baseline that included areas of the upper abdomen. Attenuation coefficients in HU were measured in four areas of the liver and two areas of the spleen. Measurements for each area included the minimum, maximum and mean HU for a 2 cm round or ellipse region of interest (ROI) in the right and left lobes of the liver, as well as in the spleen. If sufficient tissue was not available for a 2 cm measure, a 1 cm measurement was obtained. If less than 1 cm of tissue was evident on the cardiac scan, the study was deemed not sufficient for measure. A final HU value for each liver was calculated by averaging the four ROI analyzed. Similarly a final HU value for the spleen was calculated by averaging the two ROI analyzed. A liver/spleen attenuation ratio (LS ratio) was then calculated comparing the final HU measurement between the liver and spleen on each CT scan. NAFLD was defined as a LS ratio of < 1. LS ratio < 1 has an area under the receiver operating curve (AUROC) of 0.991 when measuring hepatic steatosis > 30%, corresponding to moderate to severe steatosis on histology[28-31].

Results of summary outcome measures were reported as mean ± standard deviation and proportions. Differences between groups were tested using χ² analyses for categorical data and two sample Student’s t test for continuous variables. Logistic regression was used to determine predictors of NAFLD using univariate and multivariate analysis. In our analytical models we included a core set of covariates which included age (as a continuous measure), gender and education (measured dichotomously; completed high school yes or no). We included the variables that were significant with a P value of 0.20 or smaller on univariate analysis into our multivariate model of the entire population. All analyses were performed using Stata version 11.0 (StataCorp LP, College Station, Texas).

After applying our exclusion criteria there were a total of 788 participants available for analysis, baseline descriptive characteristics are reported in Table 1. The mean age (years) of participants was 61 ± 10 and 54% of participants were female. Of the final study population, 67% (n = 524) were of Mexican (MX) origin, 15 % (n = 121) of Dominican (D) origin and 18% (n = 143) of Puerto Rican (PR) origin. Diabetes was reported in 19% of the population. A total of 225 (29%) participants had radiographic NAFLD at baseline as defined by LS ratio < 1. Radiographic NAFLD was found in 34% of participants of Mexican origin (n = 179), 17% (n = 21) of Dominican origin and 17% (n = 25) of Puerto Rican origin (Figure 2).

Open in New Tab   Full Size Figure   Download Figure

Figure 2 Prevalence of non-alcoholic fatty liver disease by Hispanic subgroup.

There were several differences in the descriptive baseline variables between participants of Mexican and Dominican origin. When compared to participants of Dominican origin, Hispanics of Mexican origin were older, more likely to be male, have a higher BMI and have a larger waist circumference. There were also several physiologic and metabolic differences between these two groups. When compared to participants of Dominican origin, Hispanics of Mexican origin had lover HDL levels, higher triglyceride levels and HOMA insulin resistance scores. They were more likely to have metabolic syndrome but less likely to have hypertension (Table 2).

Participants of Puerto Rican and Mexican origin were similar with respect to descriptive baseline variables except that when compared to those of Puerto Rican origin, Hispanics of Mexican origin had a lower rate of high school completion. There were several differences with respect to physiologic and metabolic parameters. When compared to participants of Puerto Rican origin, Hispanics of Mexican origin had higher triglyceride and HOMA insulin resistance levels, lower HDL levels and higher rates of metabolic syndrome (Table 3).

Hispanics of Dominican and Puerto Rican origin were similar with respect to baseline descriptive values except that participants of Dominican origin had lower BMI (kg/m²) and smaller waist circumference (cm) than participants of Puerto Rican origin as well as lower rates of high school completion. With respect to physiologic and metabolic parameters, participants of Dominican and participants of Puerto Rican origin were similar except that participants of Puerto Rican origin had higher HOMA insulin resistance scores (Table 4).

Univariate analysis: Being a Hispanic of Dominican origin was associated with a significantly lower crude odds ratio for the presence of NAFLD when compared to being a Hispanic of Mexican origin. Similarly Hispanics of Puerto Rican origin had significantly lower crude odds ratio of NAFLD prevalence when compared to Hispanics of Mexican origin (Table 5).

We compared the predictors of NAFLD in individuals with NAFLD in each subgroup. There was no statistically significant difference in any predictor across groups (Table 6). When we compared the groups to each other, the only significant difference found was that Hispanics of Mexican origin with NAFLD had a significantly higher BMI than Hispanics of Dominican origin with NAFLD (P = 0.05) and Hispanics of Puerto Rican origin with NAFLD had significantly more individuals with hypertension than those of Mexican origin (P = 0.04) with NAFLD.

Multivariate analysis: Hispanics of Dominican and Puerto Rican origin had a significantly lower risk for the prevalence of NAFLD compared to Hispanics of Mexican origin on multivariate analysis after controlling for age, sex, BMI, waist circumference, hypertension, level of education, serum HDL, triglyceride and CRP levels and HOMA. Adjusted odds ratios can be seen in Table 5.

Nonalcoholic fatty liver disease (NAFLD) is the most common etiology of chronic liver disease and is projected to soon be the leading cause of liver transplants. Hispanics are significantly more likely to have NAFLD when compared to other ethnic groups. Hispanics with NAFLD are also more likely to have advanced disease steatosis and fibrosis on histology compared to other ethnic groups. As a result, it is recommended that liver biopsy should be obtained in Hispanic patients found to have NAFLD according to American Association for the Study of Liver Diseases guidelines. The term “Hispanic” applies to a very diverse group of people and it is unclear if this increased risk and therefore the need for liver biopsy is uniform.

NAFLD is the leading cause of chronic liver disease. A research hotspot in this field is being able to better define which individuals are at risk.

The majority of studies evaluating NAFLD in United States Hispanics are performed on Mexican Americans. This is the first study to compare Hispanic subgroups in the United States.

Currently guidelines recommend liver biopsy in those individuals deemed high risk for non-alcoholic steatohepatitis. Their findings allow for appropriate risk stratification among a culturally and genetically diverse group of people.

According to the US census bureau The term “Hispanic” is used to describe people who classify themselves as being of “Mexican, Mexican Am., Chicano” or ”Puerto Rican” or “Cuban” - as well as those who indicate that they are “another Hispanic, Latino, or Spanish origin”. They further state that origin can be viewed as the heritage, nationality group, lineage, or country of birth of the person or the person’s ancestors before their arrival in the United States and people who identify their origin as Hispanic, Latino, or Spanish may be of any race.

This is a cross-sectional observational study to compare prevalence rates of NAFLD between the two largest subpopulations of Hispanics. NAFLD was diagnosed by computed tomography. The results of this study show that Hispanics of Mexican origin had a significantly higher prevalence of NAFLD than Dominican or Puerto Rican origin.