Firm glucose control may diminish CV benefit in patients with diabetes, comorbidities

Evaluation of comorbidities may be beneficial when tailoring glucose-lowering therapy in diabetes.

Strict control of blood glucose levels in patients with type 2 diabetes and serious comorbidities did not lower their risk for cardiovascular events or mortality.

However, firm glucose control — defined as HbA1c levels <7% — reduced CV outcomes for patients with diabetes and fewer or less severe comorbidities.

“The findings reveal that strict glucose control benefits some patients but not others depending on certain factors, mainly concurrent illnesses,” researcher Sherrie H. Kaplan, PhD, MPH, associate dean of the school of medicine at University of California Irvine, said in a press release. “They also raise serious questions about guidelines advocating a single approach for all diabetics.”

The researchers reviewed data on 2,613 patients with type 2 diabetes under the care of 205 physicians in Italy. They analyzed histories of heart disease, heart failure, lung disease, urinary tract disease, arthritis, foot issues and digestive conditions. Using the Total Illness Burden Index, a validated patient-reported measure of comorbidity, researchers classified patients into high and low–to–moderate comorbidity subgroups.

During five years of follow-up, patients who attained an HbA1c level of <6.5% at baseline had a lower five-year incidence of CV events in the low-to-moderate comorbidity subgroup (adjusted HR=0.60; 95% CI, 0.42-0.85). However, the incidence was increased in the high comorbidity subgroup (adjusted HR=0.92; 95% CI, 0.68-1.25).

A baseline HbA1c level of 7% was associated with prediction of fewer CV events in the low-to-moderate comorbidity subgroup (adjusted HR=0.61; 95% CI, 0.44-0.83) but not the high comorbidity subgroup (adjusted HR=0.88; 95% CI, 0.66-1.17).

Accounting for comorbidities

Researchers said these findings suggest that guideline developers and physicians should account for a patient’s related comorbidities when determining diabetes treatment goals.

“In certain cases, doctors should aim for just moderate blood glucose levels and aggressively treat coexisting conditions,” researcher Sheldon Greenfield, MD, Donald Bren professor of medicine at University of California Irvine and co-executive director of the Health Policy Research Institute, said in a press release.

According to the researchers, these data may help explain inconsistencies in previous studies, such as ACCORD, ADVANCE and VADT, on whether a <7% HbA1c goal decreases CV events in patients with type 2 diabetes. Some data indicate it does whereas others indicate no such link.

In an accompanying editorial, David M. Nathan, MD, professor of medicine at Harvard Medical School, said with consideration of these data, future studies should include patients with fewer comorbid conditions and lower CV disease risk that in previous studies.

The researchers noted limitations of this study, including the observational nature that did not allow for causal interference, the limited length of data collection and unavailable information on clinical management.

This study was funded by Pfizer of Italy.

Greenfield S. Ann Intern Med. 2009;151:854-860.

Nathan DM. Ann Intern Med. 2009;151:888-889.