Undiagnosed disease, especially diabetes, casts doubt on some of reported health 'advantage' of recent Mexican immigrants.

Newly arrived Mexican immigrants in the United States generally report better health than do native-born Americans, but this health advantage erodes over time. At issue is whether the advantage is illusory-a product of disease that goes undiagnosed in Mexico but is discovered after immigration. Using results from the National Health and Nutrition Examination Survey, we compared clinical to self-reported diagnosed disease prevalence and found that Mexican immigrants are not as healthy as previously thought when undiagnosed disease is taken into account, particularly with respect to diabetes. About half of recent immigrants with diabetes were unaware that they had the disease-an undiagnosed prevalence that was 2.3 times higher than that among Mexican Americans with similar characteristics. Diagnosed prevalence was 47 percent lower among recent Mexican immigrants than among native-born Americans for both diabetes and hypertension, but undiagnosed disease explained one-third of this recent immigrant advantage for diabetes and one-fifth for hypertension. The remaining health advantage might be explained in part by immigrant selectivity-the notion that healthier people might be more likely to come to the United States. Lack of disease awareness is clearly a serious problem among recent Mexican immigrants. Since undiagnosed disease can have adverse health consequences, medical practice should emphasize disease detection among new arrivals as part of routine visits. Although we found little evidence that health insurance plays much of a role in preventing these diseases, we did find that having health insurance was an important factor in promoting awareness of both hypertension and diabetes.