Even though Booth thinks universal drug coverage helps explains the findings, she said it is not the sole reason for the gap between the rich and poor.

“It’s more complicated than that,” Booth said. Diabetes is a complex condition that requires people to keep up a healthy lifestyle, and tackle daily tasks like measuring blood sugar.

So differences in diet, exercise, smoking and general “health literacy” - a person’s ability to read and understand information about a health condition - are all important, according to Booth.

“Drug coverage is one piece,” she said. “We think it’s an important piece, but it’s not the only one.”

Booth also said she thinks her findings are relevant to other countries, including the U.S., where the Medicare program for older Americans has covered the cost of prescriptions since 2006.

Studies have shown that since that benefit started, Medicare recipients’ adherence to their medications has generally improved. That includes the poorest and sickest beneficiaries.

Those studies have also found that “non-drug” spending - mostly for hospitalizations - has declined among Medicare recipients who previously had only limited drug coverage.

Medicare drug coverage is subject to coverage gaps, in which seniors have to pay full price for their prescriptions. Recent studies have found that participants often drop their medications when they hit that so-called “donut hole” in coverage, but have not documented any health consequences from that choice. (See Reuters Health stories of July 2, 2012 and August 17, 2012.

Still, Booth said the overall evidence argues for better drug coverage for younger people as well. “More and more people are being diagnosed with diabetes at younger ages,” she noted.

Older age is a major risk factor for type 2 diabetes, by far the most common form of diabetes. But so is obesity. And in the U.S., about 36 percent of all adults are now obese.

An estimated 26 million Americans have diabetes, including 14 percent of all people between the ages of 45 and 64, according to the Centers for Disease Control and Prevention.

SOURCE: Diabetes Care, online August 13, 2012.