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Excess Mortality from Cardiovascular Causes in Type 1 Diabetes

Degree of glycemic control is investigated for excess risk of death due to cardiovascular cause….

When compared to the general population, patients with type 1 diabetes are at increased risk of premature death. The most common cause of death is cardiovascular disease in patients over thirty years of age. Adequate glycemic control lowers the risk of such complications. Over 20% of type 1 diabetes patients however have poor glycemic control with an HbA1c of greater than 8.8%. Previous studies have not been performed to assess the effect varying glycemic control has on excess risk of death from cardiovascular disease.

This study used the Swedish National Diabetes Register to assess how varying degrees of glycemic control impact excess risk of death from any cause and cardiovascular disease when compared to the general population. Type 1 diabetes patients were selected and then matched to five controls by age, sex and county. A Cox regression model was used to measure the association between type 1 diabetes patient outcomes and their level of glycemic control. A total of 33,914 patients with type 1 diabetes were included along with 169,249 matched controls. The average HbA1c at baseline was 8.2%.

A higher proportion of type 1 diabetes patients died from any cause compared to the controls (8.0% vs 2.9%, aHR 3.52, 95% CI 3.06 to 4.04) as well as a result of cardiovascular disease (2.7% vs 0.9%, aHR 4.60, 95% CI 3.47 to 6.10). Those with an HbA1c of 6.9% or lower were still at an increased risk of death from a cardiovascular cause (aHR 2.92, 95% CI 2.07 to 4.13). The risk increased as the HbA1c became less controlled and higher (HbA1c 7.0 to 7.8%- aHR 3.39, 95%CI 2.49 to 4.61. HbA1c 7.9 to 8.7%- aHR 4.44, 95% CI 3.32 to 5.96. HbA1c 8.8 to 9.6%- aHR 5.35, 95% CI 3.94 to 7.26. HbA1c 9.7 and higher- aHR 10.46, 95% CI 7.62 to 14.37).

The results of this study show that those with type 1 diabetes are at increased risk of death from any cause including cardiovascular causes when compared to the general population. Even for those with well controlled glycemic levels, the risk was twice as high as the general population. Even though type 1 diabetes patients with adequate glycemic control are at increased risk of death, strict glycemic control still needs be advised. As the results show, the risk of death from cardiovascular cause increased dramatically as the HbA1c levels became less controlled.

Practice Pearls:

  • The most common cause of death in type 1 diabetes patients over the age of thirty is from a cardiovascular cause
  • Patients with type 1 diabetes who had an HbA1c of 6.9% or below still had a risk twice as high for death due to a cardiovascular cause when compared to controls
  • The chances increased as HbA1c became more uncontrolled and higher

Lind M, Svensson AN, Kosiborod M, Pivodic A, Wedel H et al. Glycemic Control and Excess Mortality in Type 1 Diabetes. The New England Journal of Medicine. 2014 November 20.