Cardiovascular Benefit of Glycemic Control Is Limited to Those with Low Comorbidity

Does an HbA1c level of 7% remain an appropriate goal?

The effect of glycemic control on preventing adverse cardiovascular events has been difficult to demonstrate, possibly because such effects are limited to particular patient subgroups.

To determine whether achieving glycosylated hemoglobin (HbA1c) targets of 7% versus 6.5% had differential effects by comorbidity, industry-sponsored researchers studied 2613 Italian patients with type 2 diabetes who received care from general practitioners or in diabetes clinics. Comorbidity was measured by questionnaire and was dichotomized at a level that was associated with excess mortality. Comorbidities included heart disease, lung disease, arthritis, genitourinary disease, vision loss, adverse gastrointestinal conditions, and foot disease.


Among patients who had HbA1c levels of <6.5%, 5-year incidence of adverse cardiovascular events was lower for those with low comorbidity (hazard ratio, 0.6) than for those with high comorbidity (HR, 0.9) in analyses adjusted for age and sex. For an HbA1c target level of 7%, the same finding was noted (i.e., lower incidence of adverse cardiovascular events only among those with low comorbidity).
Comment: When individual randomized trials have been analyzed in systematic reviews, intensive control (HbA1c <7% but not <6.5%) modestly lowered incidence of adverse cardiovascular events (mainly nonfatal myocardial infarction) at a cost of excess severe hypoglycemia.

Results of this observational study suggest that cardiovascular benefits might accrue only to those without substantial comorbidity. An editorialist concludes that 7% remains an appropriate goal to prevent adverse microvascular, neurological, and, possibly, cardiovascular events. However, for many patients with substantial comorbidity, the overall benefits of even a 7% goal might not exceed the burdens or harms associated with trying to achieve that goal.

— Richard Saitz, MD, MPH, FACP, FASAM
Published in Journal Watch General Medicine January 26, 2010
Citation(s):
Greenfield S et al. Comorbidity affects the relationship between glycemic control and cardiovascular outcomes in diabetes: A cohort study. Ann Intern Med 2009 Dec 15; 151:854.
Original article (Subscription may be required)
Medline abstract (Free)
Nathan DM. The role of glycemia management in the prevention of cardiovascular disease — Starting over? Ann Intern Med 2009 Dec 15; 151:888.
Original article (Subscription may be required)
Medline abstract (Free)

Dato' Dr. Ismail Yaacob
Medical Director/Consultant Physician
Kedah Medical Centre