Conventional wisdom holds that children of US immigrants should lead more prosperous lives than their foreign-born parents, but recent research shows that when it comes to health, first-generation Americans are actually faring worse. As the New York Times reports, several studies have exposed an alarming discrepancy in the life expectancies of immigrants and their US-born children, with the latter demonstrating higher rates of heart disease, diabetes, and high blood pressure.

The trend is particularly sharp among Hispanics, who now comprise the largest immigrant group in the US. Among this demographic, the foreign born live an average of three years longer than those born in the US, according to several studies. It's difficult to identify a single cause for this discrepancy, but researchers say this growing body of evidence suggests that America's higher wages and better standards of living are often outweighed by a more sedentary, less healthy lifestyle.

"We have a time bomb that's going to go off."

Most agree that socioeconomic status likely plays a role. A 2011 study from Brown University found that higher smoking rates among second generation Hispanics could explain half of the three-year discrepancy between life expectancies of children and their parents. According to the researchers, US-born Hispanics are generally part of a lower income group that exhibits higher smoking and drinking rates — behaviors that immigrant children tend to adopt.

It's not clear how this trend will evolve over future generations; as second- and third-generation Americans attain higher socioeconomic levels, they may see their health improve. There's also wide variation across ethnic groups; US-born Puerto Ricans, for instance, exhibit among the shortest lifespans, which could drag down the averages for Hispanics as a whole.

Nevertheless, the numbers remain alarming. A 2006 study found that cancer mortality rates were about 20 percent lower among immigrants compared to their US-born counterparts, with mortality rates from cirrhosis about 24 percent lower. Compared to white US-born adults, Hispanics are 14 percent more likely to be obese, and exhibit even higher rates of diabetes.The implication for some, then, is that the healthy diets and lifestyles adopted in other countries tend to fade away once families relocate to the US, where fast food culture and economics tend to dominate.

"We have a time bomb that's going to go off," Dr. Amelie Ramirez, a professor of epidemiology and biostatistics at the University of Texas, told the Times. "Obesity rates are increasing. Diabetes is exploding. The cultural protection Hispanics had is being eroded."