The health of a nation’s economy and the health of its people are connected, but in some surprising ways. At times like these, when the economy is strong and unemployment is low, research has found that death rates rise.

At least, in the short term. In the long term, economic growth is good for health. What’s going on?

One study of European countries just before and during the Great Recession found that a one-percentage-point increase in the unemployment rate is associated with a 0.5 percent decline in the overall mortality rate. Other studies of Europe during different periods, as well as those of the United States, found a similar relationship between joblessness and mortality.

This is counterintuitive, since economic growth is a major factor in higher living standards. When the economy is more productive, we have more resources to promote health and well-being.

But a surging economy does more than generate greater income. An industrial economy also pumps out more air pollution as more goods are produced. Polluted air, it turns out, is a major contributor to the mortality-increasing effect of an economic boom. In their analysis of how economic growth increases mortality, David Cutler and Wei Huang, of Harvard University, and Adriana Lleras-Muney, of U.C.L.A., found that two-thirds of the effect can be attributed to air pollution alone.