Hispanic health trends in the U.S. present a bit of a puzzle for epidemiologists. As a demographic group, Hispanics are similar to American blacks in factors that normally affect health—education, income, and poverty—but their health outcomes more closely resemble those of whites. This is known as the Hispanic paradox: lower mortality despite lower social and economic status.

In 2013, non-Hispanic whites died at a rate of 747 per 100,000, while for Hispanics the rate was 567, according to the CDC. The difference can’t be explained completely by older immigrants leaving the U.S., skewing death records. Researchers who examined infant mortality among Mexican immigrants found lower rates than whites.

Demographers offer a number of possible explanations for the paradox. Tight family and community networks might support better health, or people who choose to migrate might be in better shape overall. Hispanics also smoke less than whites. Whatever the explanation, it seems that the advantages may erode as families become assimilated and generations born in the United States adopt American lifestyles rover those of their parents. “People’s genes don’t change when they come to this country,” CDC Director Tom Frieden said on a call with reporters. Behavior and lifestyle influence health.