ATLANTA -- Mexican-Americans living in the United States demonstrated more risk factors for liver cancer than their counterparts in Mexico, according to results of a study presented at the 10th AACR Conference on The Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved, held here Sept. 25-28.
"Liver cancer incidence and mortality have been on the rise in the United States, despite a steady decline in overall cancer incidence and mortality over the past 15 years," said the study's lead author, Yvonne N. Flores, PhD, associate professor at the UCLA Cancer Prevention and Control Research Center, Fielding School of Public Health and Jonsson Comprehensive Cancer Center, and the UCLA Kaiser Permanente Center for Health Equity. "Chronic liver disease, which can lead to liver cancer, is a leading cause of mortality in Mexico and among people of Mexican descent living in the United States. We wanted to compare the prevalence of risk factors in these two groups."
Flores and colleagues examined data for Mexican-Americans living in the U.S. from the 1999-2014 National Health and Nutrition Examination Survey; and data from Mexican residents from the Health Worker Cohort Study, conducted from 2004 to 2006, with follow-up conducted from 2011 to 2013. The total study sample included 13,798 individuals -- 9,485 Mexicans residing in Mexico; 2,324 U.S.-born Mexican-Americans living in the United States; and 1,989 Mexican-Americans who were born in Mexico and now live in the United States.
They evaluated the participants for the primary known risk factors for liver disease, including infection with hepatitis B or C virus, metabolic syndrome, high total cholesterol, diabetes, overall obesity, abdominal obesity, and heavy alcohol use.
After controlling for age, marital status, and education level, the results showed that Mexican-American men and women were more likely to be obese (overall and abdominal obesity), diabetic, and heavy drinkers than those born and living in Mexico.
The results were reversed for hepatitis B or C infection. The study showed that Mexican-American men and women were less likely to have hepatitis B or C infections than their counterparts in Mexico.
Flores said it is important for health care practitioners to be aware of the numerous risk factors that may lead to liver disease in their patients of Mexican descent. "Having a combination of risk factors for liver disease, such as obesity and excessive drinking, or diabetes and chronic hepatitis C infection, has been shown to increase risk of liver cancer," she said. "More studies are needed to evaluate how the accumulation of specific risk factors may be contributing the increased risk of chronic liver disease in Mexican-Americans."
Flores added that other ethnic minority groups, including Asians, other Latinos, and African-Americans, also face liver cancer incidence and mortality rates significantly higher than the rates for non-Hispanic whites, and a deeper understanding of liver cancer risk factors could help inform prevention efforts.
"We need more comprehensive and precise exposure assessment approaches that can improve the prevention, early detection, and treatment of chronic liver disease, in order to delay or prevent the progression to liver cancer," she said.
Flores cautioned that further research would be necessary to determine whether the results of this study are applicable to all Mexicans and Mexican-Americans. She said the study's primary limitation is that the data from Mexico came from the Health Worker Cohort Study, so the participants may have been younger and more educated than the general public. She said the researchers consulted broader Mexican population studies and found similar overall trends.
The study was funded by grants from the Programa de Investigación en Migración y Salud, the Instituto Mexicano del Seguro Social, and the Consejo Nacional de Ciencia y Tecnologia. The authors declare no conflicts of interest.
Risk factors for liver disease/cancer among adults of Mexican descent in the United States and Mexico. Yvonne N. Flores1, Zuo-Feng Zhang2, Roshan Bastani1, Mei Leng3, Catherine M. Crespi4, Paula Ramirez5, Heather A. Stevens6, Jorge Salmerón7. 1UCLA Department of Health Policy and Management, Fielding School of Public Health, Los Angeles, California, 2UCLA Department of Epidemiology, Fielding School of Public Health, Los Angeles, California, 3UCLA Division of General Internal Medicine and Health Services Research, Los Angeles, California, 4UCLA Department of Biostatistics, Fielding School of Public Health, Los Angeles, CA, 5Unidad de Investigación Epidemiológica y en Servicios de Salud, Morelos, IMSS, Cuernavaca, Morelos, Mexico, 6University of Washington, School of Medicine, Seattle, WA, 7Unidad Académica en Investigación Epidemiológica, UNAM, Ciudad De Mexico, DF, Mexico.
Background: Latinos in the United States (US) have disproportionately higher rates of chronic liver disease (CLD). Since 2002, CLD has consistently been the sixth leading cause of overall mortality for Latinos, and the third cause of death among Latino males, ages 55-64. Latino men and women are twice as likely to have CLD and are 1.7 and 1.8 times more likely to die from liver cancer, respectively, than non-Hispanic whites (whites). The frequency of earlier stage liver disease, such as steatohepatitis, is also higher among Latinos (45%), than among whites (33%), or Blacks (24%). In Mexico, cirrhosis and other forms of CLD were the fifth leading cause of general mortality in 2015, and the third among males between the ages of 45 and 65 years. By 2050, an estimated 90% of cases of CLD in Mexico will be attributable to obesity and excessive alcohol consumption, as compared to other populations that have high rates of CLD due to infection with hepatitis B (HBV) or hepatitis C (HCV).Although infection with HBV or HCV and heavy alcohol use are well known risk factors for CLD and liver cancer, up to 50% of cases do not present these risk factors. Other risk factors for CLD include obesity and diabetes, and the proposed mechanism is through the development of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). NAFLD is found in 80-90% of obese adults, 30-50% of diabetics, and 90% of patients with hyperlipidemia. In the US, the prevalence of NAFLD and NASH is highest among Latinos, followed by whites and Blacks. Rates of obesity are also higher among Latinos (42.5%) than whites (34.5%) in the US. In 2012, approximately 69% of men and 73% of women in Mexico were overweight or obese, and these numbers are predicted to rise to 88% and 91%, respectively by 2050. The objective of this study was to compare the prevalence of risk factors for liver disease/cancer in a representative sample of Mexican-Americans who were born in the US or Mexico, to a sample of adults who reside in Mexico. We hypothesized that Mexican-Americans in the US would be at greater risk for CLD than their counterparts in Mexico. This hypothesis is based on studies suggesting that immigrant Mexican-Americans have better health outcomes than more acculturated, US-born Mexican-Americans.
Methods: Data for Mexican-Americans in the US was obtained from the 1999-2014 National Health and Nutrition Examination Survey (NHANES), a cross-sectional, representative, examination survey of the total civilian non-institutionalized population. The NHANES sample was restricted to Mexican-American participants who were 20 years and older, born in the US or Mexico, not pregnant or breastfeeding, with medical insurance. The final NHANES sample consisted of 2,097 males and 2,177 females with complete questionnaire and laboratory data.
The data in Mexico came from the Heath Worker Cohort Study (HWCS), a longitudinal study of workers and their immediate family members from two large health care institutions in Cuernavaca, Mexico: the Mexican Institute of Social Security (IMSS) and the National Institute of Public Health (INSP). Briefly, the HWCS collects information using physical examinations, self-reported questionnaires, and laboratory tests, which are comparable to those used for the NHANES surveys. From 2004 to 2006 (Wave 1), approximately 9,000 health workers enrolled in the HWCS. During 2011 to 2013 (Wave 2), a total of 1,855 participants were followed-up. The final HWCS sample consisted of 3,010 men and 6,475 women 20 years and older who reside and were born in Mexico, with complete questionnaire and laboratory data. The total study sample of 13,798 individuals consisted of 9,485 Mexican subjects who currently reside in Mexico, 2,324 US-born Mexican-Americans who live in the US, and 1,989 Mexican-Americans who were born in Mexico and now live in the US.
The following known risk factors for liver disease/cancer were evaluated: elevated aminotransferase levels (elevated ALT was defined as >40 IU/L for men and women; elevated AST was defined as >40 IU/L for men and women), infection with HBV or HCV, metabolic syndrome, high total cholesterol, diabetes, obesity, abdominal obesity, and heavy alcohol use. The main independent variables for this study classified individuals by country of residence (i.e., Mexico versus the US) and place of birth (i.e., US-born versus Mexico- born). The HWCS participants represent Mexicans who were born and currently live in Mexico. Individuals from the NHANES sample were further classified by birthplace (US-born versus Mexico-born). The following three groups were compared: (1) HWCS (Mexico resident, Mexico-born), (2) NHANES (US resident, Mexico-born), and (3) NHANES (US resident, US-born). Other independent variables included age, sex, marital status, and education level. Regression analyses were used to investigate liver disease/cancer risk factors.
Results: After controlling for age, marital status, and education level, the logistic regression results indicate that Mexico-born Mexican-American males were less likely to have HBV or HCV (OR 0.2, 95% CI 0.1-0.6) but were more likely to have high cholesterol (OR 1.4, 95% CI 1.1-1.8), than their counterparts in Mexico. US-born Mexican-American males were more likely to have metabolic syndrome (OR 1.4, 95% CI 1.1-1.9) and diabetes (OR 3.0, 95% CI 1.9-4.8), than males in Mexico. Mexican-American males were much more likely to be obese, diabetic, have abdominal obesity, or be heavy/binge drinkers, than Mexican males. The prevalence ratios and prevalence differences confirm the multivariate analyses findings and may provide more precise estimates of the increased risk of diabetes, obesity, abdominal obesity, and heavy/binge drinking observed among Mexico- and US-born Mexican-American males, as compared to males in Mexico. The probability of having any of the aforementioned risk factors is greater among US-born Mexican-Americans than among their Mexico-born counterparts.
The adjusted multivariate results for females also indicate that Mexican-American females were significantly more likely to be obese, diabetic, have abdominal obesity, or be heavy/binge drinkers, than Mexican males. The prevalence ratios and prevalence differences mirror the multivariate analyses findings for the aforementioned risk factors, showing a greater risk among US-born as compared to Mexico-born Mexican-Americans. However, the prevalence ratio results indicate that Mexico- and US-born Mexican-American females are significantly less likely to be infected with HBV or HCV than females in Mexico.
Conclusions: The results of this binational analysis indicate that Mexican-Americans in the US have more risk factors for liver disease/cancer than their counterparts in Mexico. These results can be used to design and implement more effective health promotion programs to address the specific factors that put Mexicans at higher risk of developing liver disease/cancer in both countries. This study adds to the relatively scarce literature on binational research, and provides preliminary data for future studies of migrant health in the US and Mexico. Other binational primary data collection projects with representative samples and comparable demographic, socioeconomic and health status measures are needed to further investigate the growing problem of liver disease/cancer among Mexicans in both countries.
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