More and more Americans are suffering from chronic illnesses such as diabetes and high blood pressure, often having more than three at a time. This has led to average annual out-of-pocket medical costs (those not covered by health insurance) rising from $427 per American in 1996 to $741 in 2005. Adjusting for inflation, that translates to 39 percent more out-of-pocket spending per person.

Among those 65 and older who had three or more chronic conditions, the average was $2,588 in out-of-pocket medical expenses.

Based on government survey data, 44 percent of Americans in 2005 had at least one chronic medical condition, which could include diabetes, high blood pressure, high cholesterol levels, cancer, arthritis, heart failure and others.

The rise in multiple chronic illnesses comes as obesity and sedentary lifestyles have grown more common. Obesity contributes to many chronic ailments including diabetes, a disease which has increased by about 90 percent over the past decade.