Out-of-pocket costs may be causing millions of older adults in the U.S. to cut back on prescriptions for conditions as serious as diabetes, asthma and depression, a new study suggests.

Researchers found that among more than 4,000 chronically ill adults age 50 and older, 18 percent said that costs had caused them to cut back on needed medications at least once in the past year. Fourteen percent said that at least once a month they skipped medication doses, delayed filling their prescriptions or took other measures to cut costs.

Translated to the wider U.S. population, the findings suggest that more than one million diabetics may skimp on their medication to lower blood sugar, while three million adults with asthma may cut back on drugs needed to control their disease, the study authors estimate.

The findings are published in the October issue of the American Journal of Public Health.

The new findings are “very concerning,” lead study author Dr. John D. Piette said in an interview, because they show that some older adults regularly cut back on medications needed for serious health conditions.

These conditions included those that can lead to complications like heart attack and stroke, such as high blood pressure, High cholesterol and diabetes.

But more commonly, study participants cut back on drugs for back pain, arthritis, ulcers, asthma and depression - all disorders that can significantly affect quality of life, said Piette, of the University of Michigan in Ann Arbor.

Not surprisingly, he and his colleagues found that people with lower incomes or higher out-of-pocket drug costs were particularly likely to underuse medications. Survey respondents who lacked prescription drug coverage altogether were at least three times more likely than those with coverage to cut back on medications for high blood pressure, heart disease, heartburn and back pain.

According to Piette, past research has shown that two out of three patients who skimp on medications due to costs do not tell their doctors.

He advised that patients bring up financial problems with their doctors instead of resorting to self-imposed cutbacks. Doctors may be able to switch patients to generic drugs or provide information on payment assistance programs.

In addition, some patients may shortchange themselves on medication for reasons other than ability to pay. Not all low-income people cut back on their prescriptions, Piette noted, while some with relatively high incomes do. That implies that some older adults may not fully realize the importance of taking their prescriptions.

The new Medicare prescription drug plan may help alleviate some of the problem of medication underuse, according to Piette.

On the other hand, he pointed out, study participants in their 50s were more likely than those age 65 and older to cut back on medication, and Medicare reform does not affect that younger group.

SOURCE: American Journal of Public Health, October 2004.