New research has uncovered one reason for the alarming rise in credit card use among older Americans: medical bills. When people age 50 or older experience “health shocks” – newly diagnosed medical conditions – their credit card balances rise, according to research published in the Journal of Consumer Affairs. The worse the medical condition, the more they charge. A mild, new medical problem, for example, adds $230 to credit card bills – that’s a 6.3 percent increase on a starting balance of $3,654. If the new condition is severe, balances increase by $339, or 9.3 percent. Separately, the researchers looked at the effect of out-of-pocket medical costs, such as copayments for doctor visits and prescriptions not covered by private insuranc…