Can early control of blood sugar levels reduce the risk of heart disease?

Patients with type 2 diabetes are advised to control blood sugar levels as early as possible. Medications, such as metformin (Glucophage), are used together with changes to diet and exercise. It is recommended that patients maintain an HbA1c level (average blood glucose over 3 months) of less than 7% to prevent complications. High blood sugar levels can lead to complications such as kidney and heart disease. It is not clear whether or not early control of blood sugar levels can decrease the risk of developing heart disease. 

This study examined the medical records of 24,752 T2D patients who had started using metformin in Northern Denmark between 2000-2012. Six months after starting treatment, the patients were divided into five groups depending on their HbA1C levels. After an average of 2.6 years, the rates of heart  attack, stroke or death (from any cause) were compared between the groups. 

Compared to those with a HbA1C below 6.5%, those with a HbA1C between 6.5 and 6.99% were 18% more likely to experience heart attack, stroke or death (from any cause). Those with HbA1C levels between 7.0 and 7.49% were 23% more likely. Those with levels between 7.5 and 7.99% were 34% more likely. Those with levels greater than 8% were 59% more likely.

Among those who initially had HbA1C levels above 7.5%, those who managed to reduce their levels by 2-4% were 2 to 20% less likely to experience heart attack, stroke or death.

This study concluded that T2D patients who manage to control their blood sugar early are less likely to develop heart disease.

This study can only demonstrate associations. Further trials are needed to show a cause-and-effect relationship. This study also did not measure factors such as weight, diet, physical acitivity, social support, motivation or self-care. All of the above factors can also affect blood sugar levels.