Lead researcher Bruce Stuart of the University of Maryland said Medicare patients in the northern regions of the nation spent more for Part D drugs for diabetes and heart failure and tended to adhere better to taking them than did patients in the South.
All of the 10 lowest-spending areas were in southern states, and all of the 10 highest-spending areas were in northern or central states.
Of the 50 lowest-cost regions, 43 were south of the 37th parallel, which extends roughly from the Virginia-North Carolina border to central California, and 43 of the 50 highest-cost regions were above that line, Stuart said.
Researchers did not find any strong evidence of Medicare savings in treating diabetes and heart failure -- savings such as lower hospital costs or fewer medical services -- as a result of higher Part D spending, Stuart said.
"However, this is only half a story because there are several plausible conjectures behind these findings," Stuart said in a statement. "The Part D program came into play in 2006 and for many of the people who got the benefit, this could be the first time they were using the drugs."
Also, these drugs are primarily for long-term benefit. "The answer is likely that it takes a while for these drugs to work," Stuart added.
The study, published in the journal Health Affairs, found regions in the South with lower medication adherence had higher average Medicare spending for all A and B services -- doctors visits, hospitalization, preventive medicine -- compared with northern regions.