HONOLULU, April 25 – For years, scientists have been puzzled by reports that Mexican Americans, who have high rates of obesity and diabetes, are less likely than Caucasians to die from heart disease. Now a new study challenges the so-called “Hispanic paradox.”
Researchers found higher rates of heart disease deaths in Mexican Americans than in non-Hispanic whites, according to a study presented today at the American Heart Association’s Asia Pacific Scientific Forum.
Kelly J. Hunt, Ph.D., a postdoctoral fellow at the University of Texas Health Science Center in San Antonio, led the study that compared death rates of elderly Hispanics and non-Hispanic whites. Researchers found that U.S.-born Mexican Americans were more likely to die from all causes than non-Hispanics, and more likely to die from heart disease than non-Hispanics. Mexico-born Hispanics were at least as likely to die, or to die from heart disease, as non-Hispanics.
“We are not surprised by the results, but this is only one study, and it needs to be replicated in studies that follow individuals over time,” says Hunt. “However, if the “Hispanic paradox” is false, it is important to establish this.
“Hispanics are the largest and fastest-growing minority group in the United States, and Mexican Americans are the largest sub-group of Hispanics. It is important not to underestimate the burden of disease in this population,” says Hunt.
The Hispanic paradox is widely recognized by epidemiologists and public health researchers. It has been documented among Hispanics, but the enigma has been especially recognized among Mexican Americans. Nonetheless, there have been few studies of heart disease and cardiac mortality rates in which Hispanics born in Mexico and in the United States were compared with non-Hispanic whites.
Hunt and her colleagues compared all cause and heart-related death rates in 845 U.S.-born Mexican Americans, 182 Mexico-born Mexican Americans and 678 non-Hispanic whites. They were between the ages of 50 and 64 when they enrolled in the San Antonio Heart Study. They were followed from their enrollment until 1999 for an average of 13.5 years. Because migrants tend to be healthier than non-migrant populations, the researchers separately compared rates for Mexico- and U.S.-born Hispanics with those of non-Hispanics.
To compute death rates, earlier studies have typically used denominator information from the U.S. Census, with vital status (numerator) information supplied from a state bureau of vital statistics or the National Death Index.
Because they have not followed individuals over time, earlier studies are limited by potential biases. For example, ethnic misclassification may affect the reported number of deaths among Hispanics if ethnicity is coded incorrectly on the death certificate. Additionally, Hispanics who have immigrated to the United States but died in their country would not have been counted as deaths in these studies,” says Hunt.
During the study, 365 deaths were reported, 197 from cardiovascular disease (CVD), including coronary heart disease, stroke and other circulatory disorders, with 92 from coronary heart disease. Adjusted for age and gender, U.S.-born Mexican Americans were 1.4 times as likely to die of cardiovascular disease as non-Hispanic whites, while Hispanics born in Mexico were 1.2 times as likely to die from any cause.
For cardiovascular disease, United States-born Mexican Americans were 1.7 times more likely to die from CVD and 1.9 times more likely to die from coronary heart disease than non-Hispanic whites. Mexico-born Mexican Americans were 1.5 times more likely to die from CVD or coronary heart disease than non-Hispanic whites.
These risk ratios indicate an increased risk among Hispanics, rather than a decreased risk as predicted by the Hispanic paradox, Hunt says.
The higher rate may be due to cardiovascular disease or cancer, and differences in established CHD risk factors, including diabetes, anti-diabetic medication use, hypertension and anti-hypertension medicine use, levels of blood fats (lipids) and tobacco smoking. Nonetheless, even after adjusting for these factors, hazard ratios remained higher for mortality from all causes when comparing Mexico- and U.S.-born Hispanics to non-Hispanics.
Hispanics face the same or higher risk of dying from heart disease as do non-Hispanics in the United States, regardless of whether they were born in Mexico, concludes Hunt.
Co-authors of the study are Roy G. Resendez, M.A.; Ken Williams, M.S.; Steve M. Haffner, M.D.; Michael P. Stern, M.D. and Helen P. Hazuda, Ph.D., all with the University of Texas Health Science Center at San Antonio, San Antonio, Texas.
NR02-1054 (EPI02/Hunt)
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