Washington - More Americans are burdened by chronic illnesses such as diabetes and high blood pressure, often having more than three at a time, and this has helped fuel a big rise in out-of-pocket medical expenses, a study released on Tuesday showed.

    With prescription drugs playing a key role, average annual out-of-pocket medical costs - those not covered by health insurance - rose from $427 per American in 1996 to $741 in 2005, researchers wrote in the journal Health Affairs.

    Adjusting for inflation, that translated to 39 percent more in out-of-pocket spending per person over that time, according to Kathryn Paez of Maryland-based health research organization Social & Scientific Systems Inc. and colleagues.

    The figures were much higher among the elderly. For example, a person insured through the Medicare program for those 65 and older who had three or more chronic conditions paid an average of $2,588 of out-of-pocket medical expenses.

    A separate report published in the journal on Tuesday showed U.S. health care spending rose to $2.2 trillion in 2007, or $7,421 per person.

    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. That compares to 41 percent in 1996.

    The study did not look directly at the causes of the increases, but there appear to be several factors.

    The rise in Americans with multiple chronic illnesses comes as obesity and sedentary lifestyles have grown more common. Obesity contributes to many chronic ailments including diabetes. U.S. health officials say the rate of new cases of diabetes soared by about 90 percent in the past decade.

    Triple Burden

    But the percentage of Americans with three or more chronic illnesses rose even more sharply.

    It jumped from 13 percent in 1996 to 22 percent in 2005 for ages 45 to 64, to 45 percent for ages 65 to 79, and rose from 38 percent to 54 percent for those 80 and older. Among all ages, it went from 7 percent in 1996 to 13 percent in 2005.

    "The burden of chronic conditions is becoming heavier. People who already have chronic conditions no longer just have one. Now they might have three," Paez said in a telephone interview.

    Chronic disease accounts for three-fourths of the more than $2 trillion spent on health care yearly in the United States.

    The chronic disease increase was seen not just among the very oldest age groups but also in middle age and early old age - regardless of sex, race, ethnicity and income level.

    President-elect Barack Obama takes office on January 20 with plans to try to tackle the rising costs of the U.S. health care system, the world's most expensive. This study suggests that growing amounts of chronic illness may complicate his efforts.

    The increase in out-of-pocket medical expenses reflects not only more chronic illness, but likely other factors as well, including worrisome levels of people with no medical insurance as well as reduced coverage from some employers, Paez said.

    The higher costs may make it harder for some people to pay for needed medications - and they may not stay on them or skip doses, worsening their medical problems, Paez added.

    The findings were based on nationally representative surveys of about 32,000 people in 2005 and 22,000 people in 1996.

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    Editing by Maggie Fox and Cynthia Osterman.