THURSDAY, Jan. 29, 2015 (HealthDay News) -- People with diabetes are less likely to take their diabetes medications if they've been diagnosed with cancer, researchers report.
The new study included more than 16,000 diabetes patients, average age 68, taking drugs to lower their blood sugar. Of those patients, more than 3,200 were diagnosed with cancer.
"This study revealed that the medication adherence among users of [blood sugar-lowering drugs] was influenced by cancer diagnosis," the researchers wrote.
"Although the impact of cancer was more pronounced among cancers with a worse prognosis and among those with more advanced cancer stages, the difference in prognosis associated with these cancers seemed to only partly explain the impact of cancer on medication adherence," they added.
To determine the impact, the Dutch and Canadian researchers analyzed the patients' medication possession ratio (MPR), which represents the amount of medication patients had in their possession over a certain period of time.
In this study, a 10 percent decline in MPR translated into three days a month where patients did not take their diabetes medications.
At the time of cancer diagnosis, there was an overall 6.3 percent drop in MPR, followed by a 0.20 percent monthly decline following a cancer diagnosis.
The researchers also found that MPR rose about 2 percent after a prostate cancer diagnosis and fell only 0.5 percent after a breast cancer diagnosis. Large drops in MPR occurred among patients with liver (35 percent), esophageal (19 percent), lung (15.2 percent), stomach and pancreatic cancers, as well as those with late-stage cancer (10.7 percent).
For each extra month after cancer diagnosis, the largest declines in MPR were seen in patients with pancreatic cancer (0.97 percent) and in those with late-stage cancer (0.64 percent).
The research was led by Marjolein Zanders, of the Netherlands Comprehensive Cancer Organization in Eindhoven, and Jeffrey Johnson, of the School of Public Health at the University of Alberta in Edmonton. The findings were published Jan. 28 in the journal Diabetologia.
Cancer patients with diabetes are also much more likely to die than those without diabetes, and part of that might be explained by the decline in medication adherence, the researchers noted in a journal news release.
"In future studies, the reason for the decline in MPR needs to be further elucidated among the different cancer types -- is it the patient who prioritizes the fight against cancer or the advice of the physician to stop the treatment?" they wrote.
The American Academy of Family Physicians has more about diabetes.