But when the researchers plugged in a number of other variables, such differences disappeared.

In a multi-state study of assisted living, for instance, University of North Carolina researchers found that a host of variables—the facility's type, size or age; whether achain owned it; how attractive the neighborhood was—had no significant relationship

What we have to do is make sure we know what these are and take into account all the possible variables

I suspect that some experts in the field will be keen to address alternative explanations, such as unassessed variables playing a role in the well-being decline.

So what other variables could be used if the racial concept is thrown out?

These prior efforts all examined the degree to which different environmental, social, and geographic variables correlated with a number of languages found in a given location.