Many trials over the last decade have suggested little cardiovascular benefit from treating diabetics to aggressive HbA1c levels of 6.5-7.0%.  However, post hoc analyses and other meta-analyses have suggested that a benefit may still be possible if treatment is started before diabetes has become well established.

Greenfield and colleagues conducted a five-year longitudinal observation study to of patients with type two diabetes to determine whether obtaining haemoglobin HbA1c targets of 6.5% or less or 7.0% or less for glycaemic control at baseline led to any clinical benefits for patients with high (vs. low) levels of comorbidity.  Patients were initially categorized using the Total Illness Burden INdex (TIBI) into high and low-to-moderate comorbidity subgroups.

2613 patients were succesfully recruited from over 200 diabetes outpatient clinics and general practitioners clinics in Italy.  Over the course of follow-up, attaining an HbA1c level of 6.5% or less at baseline was associated with a lower 5-year incidence of cardiovascular events in the low-to-moderate comorbidity subgroup (adjusted HR, 0.60; p=0.005) but not in the high comorbidity subgroup (adjusted HR, 0.92; p=0.61).  A similiar trend was when the HbA1c target used was 7.0%.

Conclusions:

In patients with type 2 diabetes, the benefits of aggresive glucose control may be limited in patients with high levels of comorbidity.  Comorbidity levels must be considered when deciding on glucose management in type 2 diabetics.

•    Greenfield S, Billimek J, Pellegrini F et al.  Comorbidity affects the relationship between glycaemic control and cardiovascular outcomes in diabetes.  Ann Intern Med 2009; 151: 854-860.