Income inequality is making us sick.

Well, it's not making all of us sick. Only the poorest of us.

That's what a new paper in Health Affairs by Hilary Seligman, Ann Bolger, David Guzman, Andrea López, and Kirsten Bibbins-Domingo found they looked at when people go to the hospital for hypoglycemia (low blood sugar).

The basic idea is that people struggling to make it paycheck-to-paycheck (or benefits-to-benefits) might run out of money at the end of the month—and have to cut back on food. If they have diabetes, this hunger could turn into an even more severe health problem: low blood sugar. So we should expect a surge of hypoglycemia cases at the end of each month for low-income people, but not for anybody else. That's what researchers found when they looked at the numbers for California between 2000 and 2008.

Okay, but isn't it possible that poorer people just tend to be less healthy in general? Sure. That's why the researchers also looked at when people go the hospital for appendicitis, which doesn't depend on diet. So there shouldn't be any end-of-the-month increase for low-income people if tight budgets are the problem. There wasn't. Appendicitis cases were flat across the month for both high (blue) and low (purple) income people.

In other words, poorer people don't need more care at the end of the month for every kind of condition. Just the ones that get worse when you don't have enough to eat.