Could overcontrol of glucose levels be a bad thing?

This study examined the associations between blood glucose levels, other medical conditions, and mortality risk in patients with type 1 or 2 diabetes.

The main treatment focus for types 1 and 2 diabetes is glycemic control: controlling the levels of blood glucose (sugar). For patients with diabetes, this often means replacing the insulin (the hormone that breaks down the glucose taken in from food) that the body cannot make or is not sensitive to. The target HbA1c level (a measure of average blood glucose over 3 months) for a diabetic patient is approximately 6.5%. However, some studies have found that diabetic patients with intense glycemic control, meaning HbA1c levels lower than 6.0%, have higher mortality rates than patients with HbA1c levels between 7.0% and 7.9%. This may be partly due to the treatments they receive, particularly in patients with other conditions such as hypertension (high blood pressure) or other cardiovascular disease. For patients with co-existing medical conditions a higher target HbA1c level may be more appropriate. 

The current study examined the association between HbA1c levels, concurrent medical conditions, and mortality risk in patients with long-standing type 1 or 2 diabetes. This authors analyzed the records of 8820 patients with recorded type 1 or 2 diabetes, as well as hypertension, depression, coronary artery disease (narrowing of the blood vessels to the heart), or congestive heart failure (the heart cannot pump enough blood through the body). HbA1c levels were recorded quarterly for each patient, and patients were followed for an average of 9 years.

At the start of the study, 54% of patients had diabetes plus at least one of the mentioned conditions. By the end of the study, 85% of patients had at least one of the mentioned conditions.

The average HbA1c level over the study was 7.88%. Patients with an HbA1c level less than 6.4% were 45% more likely to have died during the nine year follow-up period than were patients with HbA1c levels between 7.1% and 7.5%. Of those patients with HbA1c levels less than 6.4%, those with congestive heart failure were 5 times more likely to have died, and those with both congestive heart failure and depression were 6.34 times as likely. Patients with HbA1c levels higher than 8.7% were 36% less likely to have died during the study compared to those with HbA1c levels between 6.9% and 7.7%.

This study concluded that adults with HbA1c levels less than 6.4%, with co-existing medical conditions to diabetes, had a higher mortality risk than did those with higher average blood glucose levels.

Consult with your physician if you are worried that your blood glucose levels may be too low.